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Help with Cam selection (again)

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Sonic Silver View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic Silver Quote  Post ReplyReply Direct Link To This Post Posted: Oct/09/2018 at 11:52am
Originally posted by AMXrated AMXrated wrote:

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.
They are probably concerned about suggesting too small of a cam with your compression ratio. I would lean toward the smaller of those 2, if not a bit smaller.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken_Parkman Quote  Post ReplyReply Direct Link To This Post Posted: Oct/09/2018 at 2:35pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JERSEYJOE Quote  Post ReplyReply Direct Link To This Post Posted: Oct/09/2018 at 4:33pm
I would stay wit something abound 224-228 degrees at .050 and lift in the .500 range max 112 centers
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SPEED COSTS MONEY HOW FAST DO YOU WANT TO GO?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMXrated Quote  Post ReplyReply Direct Link To This Post Posted: Oct/09/2018 at 10:33pm
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! 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Oct/10/2018 at 6:05am
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.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post Posted: Oct/10/2018 at 5:23pm

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. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMXrated Quote  Post ReplyReply Direct Link To This Post Posted: Oct/10/2018 at 6:10pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic Silver Quote  Post ReplyReply Direct Link To This Post 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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1982AMCConcord Quote  Post ReplyReply Direct Link To This Post 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...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post Posted: Oct/10/2018 at 10:04pm
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.
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