Help with Cam selection (again)
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Forum Name: AMC V8 Engine Repair and Modifications
Forum Description: AMC-made V8 engine mechanical, ignition and fuel from basic repair to high-perf modifications
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Topic: Help with Cam selection (again)
Posted By: AMXrated
Subject: Help with Cam selection (again)
Date Posted: Oct/06/2018 at 12:53am
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Thought I would revisit my cam search in a new post. Thanks to everyone who responded to my last one. I have a bit more info this time around so maybe it will help narrowing my cam choice down. Engine is a 72 360 bored .030" over. Wiseco PTS539A3 flat top pistons. SCAT forged H-beam rods with 5.885 length New main & rod bearings New double roller timing set Heads have been reworked with new seals, guides, and springs rated to .600 lift. Have a Torker SP manifold currently but planning to go to the Performer DP 750 cfm carb Planning on headers, glass packs, and 2.5" pipes all the way back Going to port the heads once I get the new intake Electronic ignition (probably) Planning on new hydraulic lifters, push rods, ARP studs, and 1.6 rollers Have a functional cowl induction hood but no breather at this point B/W 4 spd (V-code T-10 with 2.2 first and AMC 20 diff with 3.54 positrac) The Diamond Racing CR Calculator is showing 10.26:1 Static CR with 8.3:1 Dynamic. This car is going to mostly be a weekend cruiser and realistically will not see a track very often. So, looking for a cam that gives low to mid level power and still sounds great at idle--don't want it to rattle my teeth out, but want everyone to know it is definitely not stock. I like the Lunati cams which take advantage of the AMC lifter diameter and kind of leaning toward the 703. Although the Edelbrock 7132 looks pretty good as well. Lunati recommended the 704 (probably because of the CR) but it has .569 exhaust lift and I don't know if I have clearance for that. Also, concerned about vacuum. I hope to have the pistons in next week and will check my clearance before ordering any cam, but need to make a decision soon. Does anyone have the Lunati 703 or 704 or the EB 7172 in a set-up similar to mine. If so, what do you think? Thanks. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Replies:
Posted By: AMXrated
Date Posted: Oct/06/2018 at 12:23pm
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Also, has anyone used the Howard Cam # 311451-08? Looks like they also optimize their cams based on the wider AMC lifter diameters. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: Jason1180
Date Posted: Oct/06/2018 at 5:54pm
| Call Bullet cams and get a custom grind. |
Posted By: Trader
Date Posted: Oct/06/2018 at 9:30pm
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With the 3.54 you will be wanting the low end torque for the street and your build is sound for higher RPM's so the Lunati 703 would be good but have a look at the 702 also. I don't have your build and not an expert, but from what you are stating the goals are, the 702 would take more advantage of the fuel/air supply you have and give you the tone/street performance your looking for also. Just my opinion. I would don't know enough detail to provide a manufacturer information for a custom grind myself. Just going by advertised specifications.
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Posted By: AMXrated
Date Posted: Oct/06/2018 at 11:28pm
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So how does the "custom grind" thing work? Do I need to tell them what duration/LSA/lift I want? Or, do I just tell them the parameters I am shooting for and they will figure out what I need? Sorry if that is a stupid question--I've never ordered a custom cam before. I'm having trouble just picking one out of a catalog, so I know I wouldn't feel confident telling someone how to grind one. Thanks. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: 401jim
Date Posted: Oct/07/2018 at 9:47am
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Bullet is the only way to go!!!! They are very smart towards our line of engines. I got a custom grind in less than two weeks. Awesome cam. ------------- 
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Posted By: 401jim
Date Posted: Oct/07/2018 at 9:48am
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My Hornet with a 365 inch engine does the 1/4 in 11:30,s. Love that cam. -------------
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Posted By: akimmet
Date Posted: Oct/07/2018 at 10:00am
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The cam company will come up with the specific grind details. They will want to know about your car and engine build. Most of the information needed is in your first post. Car weight and rear tire diameter will also be important details. |
Posted By: Red Devil
Date Posted: Oct/07/2018 at 11:03am
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Most really mean a "custom order" cam when they say a "custom grind". The cam manufacturer picks from their library of lobes to suit your engine build, drivetrain specs, car weight, application and desired cam type (hydraulic flat tappet, mechanical flat tappet, hydraulic roller, mechanical roller). It usually helps if you have a pretty good idea of the basic cam specs you want. Many go this route when an off-the-shelf cam doesn't exist for their application - similar to getting a tailored suit when off-the-rack doesn't fit. A "custom grind" would typically be a one-off special lobe profile for an all-out race application or a new lobe profile for an odd combination where existing lobe profiles don't work. Crane used to list pricing in their catalogues for custom-grind development work - a bunch more than a custom order. Hope this helps,RD
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Posted By: PHAT69AMX
Date Posted: Oct/07/2018 at 11:27am
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Since it is a "Hobby Car" not a "daily driver" may want to consider using a Mechanical Solid Lifter Cam. -------------  Link to a http://www.youtube.com/watch?v=MySiKQsmWxU" rel="nofollow - Short YouTube Burnout Video |
Posted By: AMXrated
Date Posted: Oct/07/2018 at 9:56pm
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Thanks for the suggestions. I filled out online forms for both Howards and Bullet so we will see what they have to say. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: AMXrated
Date Posted: Oct/07/2018 at 10:00pm
I'm not very familiar with solid lifter cams (or any type of cam for that matter...) but I thought they are better for higher RPM ranges. Why do you think it would be good in my application? Thanks, Jack ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
PHAT69AMX wrote:Posted By: PHAT69AMX
Date Posted: Oct/08/2018 at 10:58am
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There are many choices so it's just an opinion, to get the "definitely not stock" idle sound, use a solid lifter cam that is for higher rpms and will get "the sound" and it will also run at higher rpms if and when it is decided to do so, just an opinion... Yes lash needs checked and adjusted occasionally with Mechanical cams, but with a "hobby car" that is less frequent since they get "few" miles put on them, relatively. My car was a street car hobby car, it had a cam for rpms beyond 5500, spec was maybe 6500, and I really like that when I did go to make 1/4 mile passes, it pulled through the traps in "D" and it did not bother me at all otherwise while street driving. Then "freshened" the engine, changed cam to a "smaller" lower rpm cam and afterward it was very aggravating the few times I went to the track and it fell on it's face at 5200.... and no real difference with normal street driving... ------------- Link to a http://www.youtube.com/watch?v=MySiKQsmWxU" rel="nofollow - Short YouTube Burnout Video |
Posted By: 67 Marlin
Date Posted: Oct/08/2018 at 1:00pm
| It would be cool if there was a sticky thread where people could put 10 second videos of their idle and which cam they had in their set up, brief build info, etc. To more fully contribute to this question, I would say to call Mike Jones and see if he can grind something to your liking. |
Posted By: PHAT69AMX
Date Posted: Oct/08/2018 at 1:33pm
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My burnout video with the link in my signature block is with the "smaller" lower RPM cam, an Elgin Super Stock E1041P , specs were: 218 deg dur at .050", 2,000 to 4,800 RPM Range. The old cam, hydraulic, I have no video of sadly, and it sounded a lot "cooler" and it had 227 / 246 deg dur at .050", .512" / .529" at Valve... and was a lot more fun, to me anyways... ------------- Link to a http://www.youtube.com/watch?v=MySiKQsmWxU" rel="nofollow - Short YouTube Burnout Video |
Posted By: Red Devil
Date Posted: Oct/08/2018 at 2:38pm
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Main reasons I like a mechanical lifter cam for a seldom-driven street car: - no lifter bleed down, so no start-up rattle (other than the soft clickity-clack with standard lash) - can run a more aggressive cam since seat duration is less as valve doesn't start to move until it takes up lash - may have better metering of oil to top end (depending on lifter) - better higher rpm lifter stability - sounds cool ... but not sure who's making good solid flat tappets or solid rollers these days and not many off-the-shelf cams? Hope this helps,RD
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Posted By: AMXrated
Date Posted: Oct/09/2018 at 9:35am
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Heard back from Howards and Bullet. Here is what they are suggesting in a custom cam: Howards: .523/.520 valve lift 225/235 @ .050 279/289 advertised duration 112 lobe separation 108 intake centerline Bullet: Intake 236 @.050 .350” lobe lift, .560” with 1.6 rocker 283 duration @.006” Exhaust 244 @.050 .350” lobe lift, .560” with 1.6 rocker 294 duration @.006” 112 lobe separation 108 intake centerline IO 10 IC 46 EO 58 EC 6 Anyone have any thoughts on those recommendations? Thanks. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: Trader
Date Posted: Oct/09/2018 at 11:20am
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My first thoughts are what is the projected RPM range of these profiles? A total guess would be 2000+ to 5800+ and you will not have much low end street torque. Of the 2 the Howards looks more streetable.
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Posted By: 67 Marlin
Date Posted: Oct/09/2018 at 11:21am
| Those sound like pretty big cams for low to mid range power, which is what you said you were looking for. Did they say where the peak HP would be? I'd guess around 6K if those .050 numbers aren't exaggerated for appearance purposes. But heck, if you have a four-speed and gears, you can always rev the thing up at low speeds and scorch the tires that way, especially with a lighter car. Whichever way you go, I'm sure you're going to end up grinning like a righteous idiot every time you touch the gas pedal! |
Posted By: AMXrated
Date Posted: Oct/09/2018 at 11:42am
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They seemed like pretty big cams to me as well compared to what I've been looking at. I gave them the exact specs listed in my original post and noted that I wanted low to mid RPM power. I think my build specs probably lean more toward high RPM use so maybe they were just trying to optimize that. I'm going to reply to them and ask what RPM range they are targeting. Thanks. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: Sonic Silver
Date Posted: Oct/09/2018 at 11:52am
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Posted By: Ken_Parkman
Date Posted: Oct/09/2018 at 2:35pm
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As a ballpark I do not suggest more than 230 degrees intake on a hydraulic. Above that means you are looking for pretty serious power at rpm levels that get problematic for a hydraulic lifter. My opinion is only go bigger than that with a hydraulic is when the rules require it. Can it be done - yes. My opinion is if you want a cam that big go to a solid, and add 8-10 degrees to compensate for the different take up ramp. A solid will have a better rpm band, both high and low as the idle will be better with an equivalent solid. I did break my own guideline on my own build with a 232 degree cam, but not by much. There are also some efforts to mitigate the hydraulic problems with light valves, beehives, and good rocker gear. It worked, and the engine pulls clean to 6500 without obvious signs of lifter collapse. The power curve does not nose over. It made 567 hp @ 6050 rpm. The discussion of how it sounds is a different one. So to me 236 is a pretty radically big cam for a hydraulic. |
Posted By: JERSEYJOE
Date Posted: Oct/09/2018 at 4:33pm
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I would stay wit something abound 224-228 degrees at .050 and lift in the .500 range max 112 centers ------------- 1985 J-20 PLOW TRUCK 1977 CJ 7 360 T-18 D 300 1970 AMX ex-SCCA car SPEED COSTS MONEY HOW FAST DO YOU WANT TO GO? |
Posted By: AMXrated
Date Posted: Oct/09/2018 at 10:33pm
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Bullet Cams said the cam they spec'd would have best power between 2,500-5,500 RPM with 6,000 being about the max. Howard estimated 2,000 - 5,500 RPM. Not sure either qualifies as "low" as in "low to mid level power". But I suppose everything is relative... Probably my fault for not giving them a target RPM range to work with. It's been a long time since I did any real engine work or owned a performance vehicle--What is a good RPM range for "hot street"? 1,500 to 5,000? Seems like I'd want it to idle around 750-800, right? Also, think I want to stay with hydraulic lifters. The solids are interesting, but don't think I want to have to worry about adjusting them even though the car probably won't see a lot of use. A lot of good, helpful info so far--Thanks! ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: Trader
Date Posted: Oct/10/2018 at 6:05am
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1500-1600 bottom and 5500-6000 top would be my aim. Idle with this would have to be about 800 as you state. You won't get full use of the 750 CFM carburetor but that's not the point of what you state you want the car for. A 650 CFM would be a better match but not worth the change for the little difference it would make, and you already have a 750. |
Posted By: Greyhounds_AMX
Date Posted: Oct/10/2018 at 5:23pm
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Those two custom cams are using wide lobes in order to get the DCR down, as the static CR is so high. I'd try to get the static CR down then take another look at cam selection. Probably the easiest way is to open up the combustion chambers to 62-65 cc, as the de-shrouding will give you more flow anyway. In my opinion the EVO number of 58 is just too high for your application. That's going to bleed off cylinder pressure and kill low RPM torque, trading it for reduced high RPM pumping losses. And it will also be ludicrously loud. Not simply lumpy/rumbly, but ear splitting, wife complaining, neighbors calling the cops kind of loud. Even the EVO of 54 from the Howards cam is just too much. Howards was using their standard 842 lobes on that custom cam too, not their 904 Mopar lobes. An easy way to spot their 904 lobes is that the duration at 0.050 numbers are even numbers, while all of their other lobes have odd numbers. I think they actually call them Mopar 0.903 lobes.------------- 1968 AMX 390 w/T5 |
Posted By: AMXrated
Date Posted: Oct/10/2018 at 6:10pm
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Well...now I'm worried. Not so much about the wife or neighbors, but I don't want my eardrums split. I was trying to compensate for the lower CR AMC implemented in the 72 360, but obviously have went too far with the Wiseco flat tops. Probably why guys build their engines around the cam and not the other way around. Geez, I really don't want to have to machine the chambers on the heads--just got them back from the machine shop..I think before I do that, I'd like to take a shot with a stock cam and see what the result is. If I have to open the heads and buy another cam later, then so be it. I'm already over budget on the engine work any way. Based on the replies I have received on this post, here is what I think is a summary of recommendations on what I should be looking for: Duration @ .050 of 224 - 230 max .500 lift max 112 LSA 1,500-6,000 RPM .904 lobes And (if all that is correct) I am wondering if something like the Lunati 10100702LK might be in the ballpark with these specs: Hydraulic Flat Tappet Duration @ .050: 220/226 Gross Valve Lift: .507/.527 LSA/ICL: 112/108 RPM Range: 1,600-5,800 Lobe width: .904 Obviously the lift is a bit higher than recommended, but not horribly high. I've read some reviews on it and people say they have been disappointed in the idle being smoother than expected. But, not every set-up is the same either. Anyone have any thoughts on that cam or used it in the past? Thanks.
------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: Sonic Silver
Date Posted: Oct/10/2018 at 7:10pm
| I believe Howard's also has a 223 -.480 or so lift on 114 centers. Not a modern fast acting cam, but it at least has a late closing intake, a reasonable idle, and not a tremendous amount of lift. It's similar to the Chevy 350/350 and L82 cam and also the AMC Group 19 cam I believe. That is what was considered a good hi-po replacement back when the car was new. I would appreciate Greyhound's opinion. |
Posted By: 1982AMCConcord
Date Posted: Oct/10/2018 at 8:58pm
| I'd also like to mention... I've talked to Howard's several times and they will custom grind whatever you want for only $150... and they grind in house... They don't repackage Eddy or Summit or Crane etc... So just FYI... |
Posted By: Greyhounds_AMX
Date Posted: Oct/10/2018 at 10:04pm
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I'm still hung up on the compression ratio though. With iron heads and standard 93 octane fuel 9.5:1 is what most people consider the limit. Are you going to run octane booster in every tank, or maybe race fuel? We have ethanol free 93 octane here at the pumps, but that's as good as it gets. I think someone mentioned E85, but in my mind more ethanol is not a good thing with our old tech gasket materials, fuel pumps diaphragms, etc. Granted you can back the timing off if it's pinging, but then they tend to overheat. Overheating and pinging = new pistons. Another thing to consider: The single plane intake manifold will have a more aggressive idle than a dual plane intake, so if you really want the beefiest idle sound possible you might want to go with the Torker. ------------- 1968 AMX 390 w/T5 |
Posted By: Airdrie AMX
Date Posted: Oct/10/2018 at 10:10pm
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Personally i would trust the recomendations given to you by the folks who do this for a living. Given the specs on your build i don't think either is too big, if it were me I'd go with the Howards. ------------- 72 amx javelin 401 4spd |
Posted By: Sonic Silver
Date Posted: Oct/10/2018 at 10:13pm
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Posted By: Red Devil
Date Posted: Oct/11/2018 at 8:56am
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... maybe this would be a case for a Comp Thumpr cam or similar? http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1447&sb=2" rel="nofollow - http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1447&sb=2 From Comp Cam's Lobe Profile Catalogue (if Greyhound'sAMX wants to plug numbers into his spreadsheet for comparison)   ... or best to go with advice from the cam companies. Can always ask them for another option if you don't like their first suggestions. A bit of back-and-forth to narrow in on the right cam is typically worthwhile. Hope this helps,RD |
Posted By: AMXrated
Date Posted: Oct/11/2018 at 9:29am
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@Red Devil: Thanks for advice--I did contact Howards & Bullet and told them that I was really looking for something that would run in the 1,600-5,500 range and idle around 800. Haven't heard back from Howards but here is Bullet's response. I will say that the guy from Bullet is on it and seems really excited about my project: From Bullet: If the compression ratio will be close to 10 to 1 (9.5-10.25) it can use some duration. Especially with this being a 4 speed. This will have a good sound and will still be Driveable with the 3.54 gear. Yes, these are .904” lobes ! Intake 231 @.050” .340” lob lift, .544” with 1.6 rocker 276 duration @.006” Exhaust 234 @.050” .335” lobe lift, .536" w/ 1.6 284 duration @.006” 112 lobe separation 108 intake centerline Duration and lift are still pushing the envelope based on some of the above recommendations, but it seems less aggressive than their first spec. Thanks. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: AMXrated
Date Posted: Oct/11/2018 at 9:45am
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@Red Devil: I did contact Comp Cam's and ask about the Thumper line of cams and they came back with a recommendation to use their XE274H. Greyhound pointed out that would be a bad choice due to my high DCR--plus the guy from Comp was complete @$$hole--very arrogant and rude. Told him I had no idea what I was doing when it came to cams and he talked down to me the entire conversation. Figured there were a lot of other cam grinders out there that might actually want my business. Guess I could give them another shot--I can deal with jerks if they have what I need... [EDIT] Sorry--I asked them about their Magnum line of cams not the Thumper (but the guy was still a jerk).
------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: Red Devil
Date Posted: Oct/11/2018 at 10:55am
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The Thumpr line of cams were designed mostly to get that "cackling" idle most like ... but they also tend to bleed off compression, have a rougher idle and lower idle vacuum. Some like them. Some not so much ... and yes, Comp tech aren't always the best to deal with. FWIW, I'm running a Bullet cam and also found them quite helpful and good to work with, so I wouldn't be afraid of going with their recommendation ... but I also don't know your tolerance level for a bigger cam ... although not overly "big" compared to some. My cam is 250@0.050", 0.616"/0.624", solid roller, a 6 speed and power brakes. Works fine for me and I'm not a racer - just wanted a fun street toy. The stick makes a big difference in cam tolerance as you can basically pick your "stall speed". May want a bit more rear gear with the 2.23 1st to slip the clutch less ... and maybe eventually a 5 speed if you do much interstate cruising ... but expect that cam should have pretty good torque. http://vid41.photobucket.com/albums/e273/RedDevil401/74%20Javelin%20AMX%20exhaust%20sound_zpsu7lq3xzr.mp4" rel="nofollow - exhaust sound Hope this helps,RD |
Posted By: PHAT69AMX
Date Posted: Oct/11/2018 at 11:28am
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This Hughes Performance Mopar page tech write-up on .904 dia Lifters is pretty good info... http://www.hughesengines.com/TechArticles/1camshaftfrequentlyaskedquestions.php" rel="nofollow - http://www.hughesengines.com/TechArticles/1camshaftfrequentlyaskedquestions.php ------------- Link to a http://www.youtube.com/watch?v=MySiKQsmWxU" rel="nofollow - Short YouTube Burnout Video |
Posted By: Greyhounds_AMX
Date Posted: Oct/11/2018 at 1:05pm
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I disabled the static compression ratio limits on the spreadsheet and then it came up with just 4 off the shelf cams. Three really, as the Elgin and Summit are the same cam. I couldn't get a very clear screen shot, so here's a link. I had it plot the smallest and largest just for fun. The revised Bullet cam came in at 8.25 DCR so it didn't make the cut. ------------- 1968 AMX 390 w/T5 |
Posted By: AMXrated
Date Posted: Oct/11/2018 at 1:20pm
THAT sounds awesome! Exactly what I am shooting for. Thanks for posting. --Jack ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: AMXrated
Date Posted: Oct/11/2018 at 1:40pm
Wow, I'm impressed. Thanks for running the numbers. Just so I understand, is there a DCR target that I need to stay below? I think when I came up with the 8.3:1 number before I used the calculator on pcengines.com and used the Lunati 703 cam specs. Looks like the cams on your spreadsheet are all below 8:1. Thanks again, Jack ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: Greyhounds_AMX
Date Posted: Oct/11/2018 at 1:56pm
Yes, there's a nice chart available courtesy of David Vizard: ------------- 1968 AMX 390 w/T5 |
Posted By: Sonic Silver
Date Posted: Oct/11/2018 at 2:10pm
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Posted By: Ken_Parkman
Date Posted: Oct/11/2018 at 2:24pm
| Be careful using dynamic compression ratio calculations, as cranking compression really tells you nothing about operating cylinder pressure and detonation resistance. Far more to it than that. |
Posted By: AMXrated
Date Posted: Oct/11/2018 at 2:32pm
Ok, think I understand. 8:1 or less is the target for 93 octane and to ensure against detonation, right? Based on that, the 3 cams in your spreadsheet should run with pump gas, correct? Looks like the Summit cam is targeting an RPM band of 2200-5500, the Crower is 1800-4500. Can't find any specs on the Erson E710018 but I would guess it is going to be close to the Crower. Sorry--I forgot to respond to your earlier question about what fuel I was going to run. 93 pump gas would be nice, but I am not opposed to running an additive or blending with E85 if it helped open my cam spec options. Thanks. [EDIT] Sorry--I think I was looking at the Summit 8601 cam specs. The 8600 has an RPM range of 1,500-5,000.
------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: AMXrated
Date Posted: Oct/11/2018 at 2:33pm
Whoops--guess I should have waited for Ken's response before asking my last question about DCR and detonation... ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: AMXrated
Date Posted: Oct/11/2018 at 2:57pm
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Noticed Crowers also has a 45243 cam that is a little more aggressive than the 45246. Duration: 228/234 Lift: .512/.525 LSA: 112 RPM Range: 1800-4500, Redline @ 5K. The 112 LSA would make for a rougher idle. Wonder what the effect on DCR would be? Greyhound, do you have that cam in your library? Maybe your spreadsheet already eliminated it. Thanks. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: AMXrated
Date Posted: Oct/11/2018 at 3:30pm
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This is interesting--I filled out Crower's online cam rec form yesterday and they just replied recommending the 45243 Cam which I just posted info on. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: Greyhounds_AMX
Date Posted: Oct/12/2018 at 10:31am
I've got pretty much every off the shelf catalog cam available for AMC V8's loaded in to the spreadsheet. There's only about 135 of them, so it's really not too much data. I've also loaded in a few interesting custom cams that folks have used. The spreadsheet calculates something called Overlap Factor, which is probably the most accurate indicator of idle quality for a given cam in a given combination. It accounts for bore size, valve size, the flow capacity of the valves in the reverse direction, etc. So the spreadsheet sorts the cams in order of increasing Overlap Factor. I extended the DCR limit to 8.3 and set the Overlap Factor range from 1.8 to 2.5, and that gives a pretty interesting group of cams to look at. I've got it comparing the 2nd Bullet custom cam with the Crower 85243. uploads/3041/AMXrated2a.pdf" rel="nofollow - uploads/3041/AMXrated2a.pdf Here's some key points that I noticed: 1) Flow Capacity: The Crower has about 4% less intake flow capacity because it's not a 904 lobe profile and runs a little less intake duration. 2) Overlap Factor: It's so close between the two cams that they should have the same idle. 3) DCR: The Crower has a lower DCR, which may allow you to run lower octane fuel. 4) EVO: The EVO for both cams is the same, and as the Overlap Factor is also essentially the same these two cams should have extremely similar power bands. 5) Intake H.I.: The Intake Hydraulic Intensity is higher (lower number) on the Bullet cam at 51, and actually in the more aggressive range as you would see on a VooDoo or Comp cam lobe. The slightly lower Hydraulic Intensity of 59 on the Crower will have lower valvetrain noise and lower risk of wear.
------------- 1968 AMX 390 w/T5 |
Posted By: Greyhounds_AMX
Date Posted: Oct/12/2018 at 10:37am
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Another thing that may help you is that for your application you can ignore the cam lift numbers. Any cam you use will be between 0.450 and 0.600 lift, and the flow rate of your heads peaks at about 0.450, so anything above that doesn't significantly increase flow. Certain relationships between duration and lift are required though in order to prevent mechanical problems, so lift will increase along with duration. There are exceptions (like dwell nose cams), but they aren't reliable or quiet enough for street use. For example, here's a comparison of the flow you will get
when using the lowly Edelbrock 2132 cam versus a much higher lift Engle,
assuming your typical ported iron AMC dogleg heads. The peak flow rates are the
same, only the increased duration adds to the flow area (the graph on the
right). The increased peak lift doesn't really matter.
If we compare the same two cams again but with ported
Edelbrock heads, you can see that the improved peak flow rates of the heads
complement the increased lift of the Engle cam.
------------- 1968 AMX 390 w/T5 |
Posted By: AMXrated
Date Posted: Oct/12/2018 at 11:00am
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"only about 135 of them...really not too much data" Ha! Thanks again for running the numbers for me. Still very impressed with the spreadsheet--I work in business analytics so I know a good one when I see it. I am really liking the specs on the Crower 45243. Based on everyone's thoughts/recommendations it seems to hit the high points. And, given the estimated DCR, it at least gets me closer to possibly using pump gas if everything else works in relation. Kind of wanted a cam that took advantage of the .904 lifter diameters, but based on the link that Phat69AMX sent, it looks like it has the greatest effect on gross lift and rate of lift if the cam is designed around that. Are there any issues running narrower lobes on the .904 lifters? Thanks again. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: AMXrated
Date Posted: Oct/12/2018 at 11:08am
The car came with a functional cowl induction hood, but the breather is missing (naturally...) and I was considering doing some mild porting on the intakes. If I were to do both/either of these things, would it be better to have some extra lift available? Or, will it have much effect on overall flow? Thanks. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: Red Devil
Date Posted: Oct/12/2018 at 11:49am
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If you read through the sticky on AMC cylinder head flows, I don't see flows stalling at 0.450" lift ... particularly with a bit of porting. http://theamcforum.com/forum/cylinder-head-flow-numbers-factory-aftermarket_topic159.html" rel="nofollow - http://theamcforum.com/forum/cylinder-head-flow-numbers-factory-aftermarket_topic159.html If you are planning some mild porting work, as someone mentioned already, you could open up the chambers to unshroud the valves, increasing combustion chamber cc which will reduce your compression. Spec on the Wiseco PTS539A3 lists 10.5:1 w/ 58cc heads. Many AMC heads measure closer to 60cc.  Flat tappet cams have a pointy nose and move across the lifter from edge-to-edge. A larger diameter lifter allows this action to start sooner and end later without falling off the edge of the lifter. That's why a 0.904" lobe profile can have a greater rate of duration increase and greater lift for same seat duration, typically translating into more cylinder pressure, more torque and more power. If you're running pump gas and have too much compression, maybe that's a negative. If worried about valvetrain loading, maybe also a negative as spring forces will be slightly higher. Most off-the-shelf AMC cams are Chevy 0.842" or Ford 0.875" lobes on an AMC core. Ultimately, tough to get a conclusive answer on a Forum unless someone is running your exact combination ... but a bigger cam is likely the right direction. Greyhounds AMX: Do you have the Comp Thumpr cams in your spreadsheet? Curious how they would compare (not recommending one ... just curious)? Thanks,RD. |
Posted By: Greyhounds_AMX
Date Posted: Oct/12/2018 at 12:07pm
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Yep, the Thumpr cams are in there, but they don't seem to fit much. Just too aggressive i think. Jack, you can certainly use 842 or 875 cams with 904 lifters. Most AMC builds with hydraulic cams are using lobes designed around 842 Chevy lifter limitations. ------------- 1968 AMX 390 w/T5 |
Posted By: AMXrated
Date Posted: Oct/12/2018 at 12:44pm
Thanks RD--That is an interesting read. If I'm reading the data right on the stock unported heads, flows don't stop after .450, but they do start to decrease at an increasing rate after that point and the gains get incrementally smaller. And, you're probably right on the cam selection--no one's going to be able to tell me what I need since everyone's set-up and preferences are different. Going to have to just make a decision and go for it. If I had to make the call right now, think I'd go with the bigger Crower. Should have the pistons in tonight (unless the wife wants to go out to dinner...). Hopefully can do a clearance check tomorrow, although it looks like the Wiseco's have pretty healthy reliefs on them so I doubt it will be a problem. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: Ken_Parkman
Date Posted: Oct/12/2018 at 1:16pm
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More lift is almost always better as long as you do not exceed durability limits. More lift is still better even if the flow separates and falls off at high lift - a typical problem with too large a valve for a given port configuration and usually happens above .25 l/d. the point is peak lift is only for an instant, but with higher lift you get more overall flow area under the curve. And flow separation characteristics on a flow bench may not be the same thing in a running engine when the delta P is much greater. Also I don't worry a lot with lifter diameter for street type applications. Yes a .904 lifter is better, but I had a conversation with a lobe designer one time and he told me there is not much in it on less than all out circumstances. to make a difference the contact patch has to move far enough from the centerline to be close to the edge. Much more of a concern on the race technology. |
Posted By: Greyhounds_AMX
Date Posted: Oct/12/2018 at 2:49pm
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That's one of the things my spreadsheet is trying to illustrate via the graph on the right side. It a plot of the flow that heads will pass at the lift of the selected cam as is goes thru the travel. The curve is then integrated to get the total area under the curve, and thats the "Intake Area" and "Exhaust Area" listed in the table. The difference in area under the curve of the two selected cams is shown on the graph. ------------- 1968 AMX 390 w/T5 |
Posted By: AMXrated
Date Posted: Oct/12/2018 at 6:08pm
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I've noticed that in many cam designs the gross lift is either the same for Intake/Exhaust or the Intake is slightly higher than the Exhaust. But in a few designs (like the custom spec'd by Bullet), the Intake is higher than the Exhaust lift. What is the effect of that? Also, I have read that AMC engines like for the Exhaust lift to be slightly higher than the Intake--is this true or just another one of those "you shouldn't believe everything you read on the internet" things? Thanks. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: jpnjim
Date Posted: Oct/12/2018 at 6:46pm
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Cam designers like to run a few more degrees of exhaust duration to help make up for a restrictive exhaust system. A lot of the time they'll choose an exhaust lobe with less intensity so it can have that extra duration, while still having about the same lift as the intake. In that case, the intake, or the exhaust lobe may have slightly more lift than the other, just the luck of the draw of using existing lobes. I'd say only the Bullet designers would know if they're actively trying to maximize intake vs exhaust lift, or if the extra intake lift is just the by-product of the more intense intake cams they are using. ------------- 71 P-code 4spd Javelin/AMX some Jeeps and some Fords |
Posted By: jpnjim
Date Posted: Oct/12/2018 at 7:42pm
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I copied your original two recommendations:
The biggest problem is the 10.26:1 CR 360 would make me want a bigger cam to get the DCR down, and 2.23 first gear T-10 with just a 3.54 rear would want me to get a smaller cam to help me pull the gear. My T-10 Javelin with a 360 had 3.91 gears and it was a chore coming out of the hole sometimes. I like the 112-114 lobe center to close the intake valve a little later, and lower the DCR without going crazy on duration. Howards cams are high quality, they make customs fast (mine took around a week) and the price is very good. Their
"Aggressive Flat Tappet Hydraulic" line of lobes are a pretty good
compromise of intensity without the higher lifts you'd end up with the
same durations in a .904 lobe. File Name @0.006" @0.020" @.050" @.200" 1.6000 lift 3HF223323 270 247 223 137 .5173 3HF225327 272 249 225 139 .5227 3HF227330 274 251 227 141 .5280 3HF229333 276 253 229 143 .5333 3HF231333 278 255 231 145 .5333 The 904 lobes have a higher intensity & a bit more lift File Name @0.006" @0.020" @.050" @.200" 1.6000 lift HM2243450A 271 248 224 144 .5520 HM2263500A 273 250 226 147 .5600 HM2283525A 275 252 228 148 .5640 HM2303541A 277 254 230 150 .5666 I bet if you went with something like the 3HF229333 276 253 229 143 .5333 on a 114 you'd be at a healthy
compromise between what the 10.26:1 compression ratio wants to run on
pump gas and what the (tallish) 7.89 first gear wants to pull a bubble
fender Javelin in first gear. If you want to drop the DNC a little, then maybe go a little bigger, or pick something from the "Standard Ramp Hydraulics" that have greater .006" duration, without bumping up the .050" duration too much: File Name @0.006" @0.020" @.050" @.200" 1.6000 lift 1hf225310 279 252 225 137 .4960 1hf225327 279 252 225 138 .5227 1hf225330 279 252 225 138 .5280 1hf227313 281 254 227 139 .5013 1hf227320 281 254 227 140 .5120 1hf227327 281 254 227 140 .5227 1hf231300 285 258 231 139 .4800 1hf231313 285 258 231 142 .5013 1hf231320 285 258 231 143 .5120 ^these
would potentially bleed off some more cylinder pressure for the same
.050" duration (since the gross, or .006" duration is higher), but they also give up duration at .200". The second lobe from the top is the intake lobe Howards chose for you, this is the exhaust: File Name @0.006" @0.020" @.050" @.200" 1.6000 lift 1hf235325 289 262 235 147 .5200 I'm not a cam designer, so I don't really have a recommendation just putting some thoughts down  Edit, it also makes some sense why Howards recommended the relatively mild 1hf225327 intake lobe, and the fairly aggressive 1hf235325 exhaust on a 112, trying to find a good balance between DNC and low end torque.
 ------------- 71 P-code 4spd Javelin/AMX some Jeeps and some Fords |
Posted By: AMXrated
Date Posted: Oct/13/2018 at 12:02am
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@jpnjim: Thanks for the thoughts/analysis. I am absolutely blown away at how much you guys know about this stuff. The last time I worried about cam specs, we called them 3/4 Racing cams...probably dating myself. I've heard really good things about Howard's, but never got a reply from the guy after I asked him to reconsider his spec's targeting a 1600-5500 RPM range. I even sent him a follow-up email this morning. ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: AMXrated
Date Posted: Oct/13/2018 at 12:50am
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Also, noticed Crower had this cam on clearance on their website. Too small for my application, but it's a good deal for $98. https://www.crower.com/clearance/amc-290-401-power-compu-pro-hydraulic-camshaft.html ------------- You can have my Hurst shifter when you pry it from my cold dead hand. |
Posted By: jpnjim
Date Posted: Oct/13/2018 at 6:27am
Your welcome, I like to try to wrap my head around the numbers sometimes, so these threads can get pretty interesting I'll give you my understanding, right or wrong here it is..... Cams are tough to figure because different manufacturers can use different points in the cam to advertise their duration at, I'm just going to type about Hydaulic Cams here because Solid Cams add even more issues to the numbers to confuse things (me!) even more. There are crazy aggressive 300 degree duration cams and very mild 300 degree duration cams, the STOCK 401 cam is very mild, but has an advertised duration of 296 intake/304 exhaust! (The stock 304/360 cam is 264/264 duration, 401 stock lift is .4576, 304/360 lift is .4256). So you can look at the advertised duration and lift and take a good guess at the cams intensity. Then you read their descriptions, which are all over the place too. Some advertise their cams in the range they best work, others list the entire range that the engine would work. So the same came could be listed as working from 2800-5500 by one company, and 2200-6000 by the other cams advertising department. Then they started using net duration. That's the .050" duration in the lists I copied earlier. .050" duration is great because its a standard point that all the manufacturers seem to be using (hydro cams), and comparing one .050" number to another .050" number is apples to apples, for the most part. If you want to figure intensity you look at the advertised duration (usually .006", but not always). A big .050" duration with a not big .006" number = a fast acting/intense cam. The .200" number would most likely back this up. How long the cam stays open past .200" says a lot about the cam's profile, the bigger the .200" number is compared to the .050" number, the more intense the cam will be. So you can have a lazy 225 degree (at .050") cam that acts like its smaller than its middle of the road numbers wpuld suggest, or you can have a pretty intense 225 degree (at .050") cam that is much faster acting ^the fast acting cam might have the same .200" duration as a slower acting 230 degree, or bigger cam so the intense cam could move almost as much, or maybe even more air during its shorter event timing. Lift tells you a lot too, but if you have the .006", .050" and .200" numbers you can start to compare them all to each other and see how it all fits togther. ^this seems to work for me, but I'm the guy who will keep reading the same thing 20 times over until I think I understand it or my brain starts to hurt. Lobe seperation is the next big thing to consider but I'll leave that for next time.  ------------- 71 P-code 4spd Javelin/AMX some Jeeps and some Fords |
Posted By: jpnjim
Date Posted: Oct/13/2018 at 6:55am
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heres an intense 224 degree .552 lobe compared to a less intense (but not mild) 231 degree .512 lobe: lobe name .006" .020" .050" .200" 1.6:1 lift HM2243450A 271 248 224 144 .5520 1hf231320 285 258 231 143 .5120 The first cam would be considered at the mild end of things with 224 net duration, but its open past .200" for 144 cam degrees of rotation, longer than the 143 degrees that the much bigger 231 cam is open. That tells you that the 224 cam is going to breath a lot better than a typical 224. Now look at the .006" numbers, the intense 224 has just 271 degrees advertised duration, that tells you it's opening quickly, closing quickly and getting its work done fast without a lot of gross duration ^that can be good for cylinder pressure (all things being equal, lobe seperation and cam advance plays a big part in this too). The more serious (but less intense) 231 cam has 285 degrees advertised/gross duration, so it would have much more overlap with it's other lobe (all things being equal), most likely lower DCR (not because of the overlap, and again, all things being equal), and it would be easier on valve components compared to the intense 224. If you didn't have all the other numbers, you could look at the 224 degree .552 lift and guess that it would be more intense than a 231 .512 lift cam. If you found a 231 degree .480 lift cam (at the same 1.6 ratio) it would be a good guess that the smaller lift cam was even less intense. Last thing, lifter size can allow for greater intensity, AMC's and Chryslers have the widest lifters of all regular production V8's, many cams were originally designed for narrow Chevy lifters, and it shows in their mild intensity and lower lifts (Small Block Chevy's use 1.5:1 rockers so that makes their valve lift lower too) ------------- 71 P-code 4spd Javelin/AMX some Jeeps and some Fords |