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'69 390 Build Advice - 500 HP/TQ Goal |
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pcking 
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Joined: Nov/06/2009 Location: W. Babylon, NY Status: Offline Points: 8 |
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 Topic: '69 390 Build Advice - 500 HP/TQ GoalPosted: Apr/24/2010 at 10:06pm |
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Greetings folks - sorry for asking what may seem like a newbie question, but I got my first AMC about 6 months ago and I am determined to do it right and it seems that there are many long time AMC'ers here and I am hoping to leverage your expertise and experience.
Just to set the stage, my car is a 1969 AMX, 390, 4 speed, 3.54 twin grip car and has all of its original sheet metal and primary drive train parts. It was soda blasted down to bare metal, coated with epoxy primer and then painted in it's original Regatta Blue and has a high quality factory style undercoating on the underside. The body is laser straight and looks 99.9% perfect from any angle and likely has better fit/finish then when it rolled if the assembly line in Kenosha. You'd be hard pressed to find a nicer '69 chassis out there - no rust and incredible paint (don't ask how much it cost). It is a very nicely optioned car with PS, PB, electric wipers, AM/FM radio, A/C, tint glass, and charcoal leather. The interior will be getting the full legendary treatment (my local upholsterer is a dealer for them) and I've collected a TON of NOS or OE parts to ensure that is stays as original as possible, both inside and outside. I realize that 500 HP is not really that tough to do with a 390, but I have some other specific things I'd like to try to stick to: > Use the stock heads (318 8558), have a 2nd set so can modify as needed (valves, porting, etc). > Use the set of Hooker Super Comp headers I have (ceramic coated, sell for $750 @ Summit) > Appear stock and more importantly fit under the hood and accept a factory air cleaner if I can. > Be highly street-able and not a full out race car (got a few of those already). The net-net here is an effort to make the car be both show and go, so I can drive it to local shows and be able to please the judges as well as enjoy driving the car. That said, I am an amateur road-racer, have been drag racing on and off for over 20 years and my daily drivers for the last 10 years have been cars with in excess of 400 HP, so I in order for this car to be enjoyable for me, I really want to have the 390 pump out close to 500 HP and be reliable for street use. While I'll likely never race the car, I want to make sure it can take on all but the most exotic street machines with ease and these days half the muscle cars rolling off the assembly line make 400 HP in stock trim. When I got the car, the engine was stripped of the intake and carb, and while I have sourced OE parts I am not necessarily attached to using them and I have a line on a nice R4B intake, but I hear that while it is a really nice piece from an originality perspective, it is not necessarily capable of my 500 HP goal. I believe that the super comps I have are designed specifically for the rectangle port heads and will not work with the later dog-legs and I'd really like to see if this is possible using stock castings, even if need to bastardize them a bit on the inside. I believe the PN on the headers is 7104-1, which I do not think Hooker even makes anymore (1 3/4" primaries into 3" collectors - plan to go 3" out the back). My engine builder and I have discussed this at length and since my block's 'worst' cylinder is about 0.007 over stock bore, we were targeting boring in 0.020 over so that I can use a 0.060 over Chevy 400 piston and just bush the small end of the rod. Having built a half dozen SBC, SBF, and other motors with him in the past, the plan would be to do a line hone, re-work the big ends of all the rods, and balance all the piston rod combos within 1/2 gram of one another. My last motor we did this way was a 306 SBF that makes 434 HP on the dyno (>1.4 HP/Cube) and revs to 7500 RPM and can live there pretty much forever. Granted it has somewhat exotic valve train and heads, but with the extra cubes in the 390, I expect I can go a bit less extreme and still hit the 500 HP/TQ target, as it amounts to a more tenable <1.3 HP/Cube. At this point the motor is ripped down and we're ready to get started, but between the rarity of some of the parts and the fact that there seems to be a lot of conflicting data out there, I am at a loss for what to do. The things I am looking for advice on are: > Is the Chevy 400 piston the way to go, or does a set of custom AMC pistons make more sense? > I am thinking full roller valve train, but with Crane going out of business, who's lifter to use? > Would going to SS/AMX specs on the valves (2.080/1.740) be advisable, or will it kill velocity? > Would an R4B even support 500 HP, or do I need to go Torker to get there? > I've read a ton about Bulltear & oiling mods - what other tips/tricks are advised for AMC 390s? I apologize in advance for the length of this post, but all too often it seems that key details get omitted and I am well aware that a it is the interaction between various components (the right combo) is the key to a successful result. If you have questions, I am pleased to try to fill in any blanks. Thanks in advance for any help you can offer - and while money is always a concern, I am willing to spend what is needed to make this a reality as I sold off a couple other toys to buy and complete the AMX as it has been a dream of mine for over a decade. |
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amx39068
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Joined: Feb/21/2008 Location: Arizona Status: Offline Points: 11576 |
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Posted: Apr/25/2010 at 9:05am |
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Despite what you may have read and heard, 500 HP is pretty a tall order and you are correct in assuming that it will be nearly impossible to get there with an R4B. Due to the .904 lifter bore, you can get a really strong performing valve train by simply going with a solid lifter cam with roller rockers.
As for you questions,
Bulltear, Wiseco and Nick Alfano all offer good pistons for the 390 (altough with Wiseco, you'd really be using a 401 piston but they have nice "K1 kits with rods and I will get to that in a minute). Nick Alfano's 390 valve relief is a great design and helps to stave off pinging and the recent set of Bulltear 401 pistons I saw at the machine shop I use appear to have a similar design.
You need to decide what you are comfortable with to get to 500hp. Are you willing to put race gas in the car when driving on the street or does it have to be pure pump gas capable? Compression makes power and the more compression you accept the more power potential you have at your disposal.
Crower makes great cams and has some excellent SS roller rockers and they will grind a cam to fit your specific application once you decide what to do.
One of my favorite and somewhat fun engine build options is to use a 401 crankshaft in the early 390. The only caveat is to be sure the pistons you use clear the 401 counter weights when using the shorter early 390 rods. You can't really use the later rods as they stick the 401 pistons out of the block too far so you can either go custom or deck the block to use a 401 crank and stock style 401 pistons. The alternative is to find a 70 390 block which is the same height as the 401 block thus enabling you to have a 390 label on the outside but all 401 on the inside.
Alternatively, Bulltear will make you any piston you want so you could stuff a 401 crank inside the engine and have them make the right piston to fit your 390 rods yet have close to zero deck which also helps support higher comrpession.
In my opinion and others may have differernt opinions, add on oiling mods are more about covering up for deficiencies elesewhere. A good front cover with the oil passages radioused and proper pump housing wall and end clearance with correct pump housing cover gasket thickness will produce excellent oil pressure that should be enough. The big weakness is in the oil pan capacity and head drain back area which seems to mostly cured with a larger pan. External oil line(s) also seem to help improve oil flow volume but you will still have the drain back issue so either regulating how much oil gets up to the heads and or increasing the drain back flow are options that some folks use. The head drain back holes are relatively small and can be enlarged and the valley on the block often has casting irregularities around the center drain holes in the valley so a little cleanup work there will be helpful as well.
420 - 450 HP is quite a bit easier to achieve and more pleasant to drive on the street so I guess in the end it all boils down to what driving characteristics are you willing to trade off for more power. 420 - 450 HP on the street is a hell of a lot of power but can be made to still be fairly civil. 500HP is still driveable but a little more unfriendly and choppy unless you want to go the spray route which quickly adds HP but has to be planned for from the start.
BTW, if you go the AMC designed piston route, .030 is much easier to find rings for.
Edited by amx39068 - Apr/25/2010 at 9:07am |
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Dan Curtis-Owner and CEO AZ AMC Restorations; Facebook: https://www.facebook.com/amcmusclecars/ & Curtis Real Estate Development
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Rebel 327
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Joined: Feb/04/2009 Location: Ohio Status: Offline Points: 596 |
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Posted: Apr/25/2010 at 9:12am |
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Quote: "....really want to have the 390 pump out close to 500 HP and be reliable for street use. "
If you already have race cars---why will you need 500HP for a "street" car? Just courious!
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Rebel 327 4-speed
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bigbad69
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Joined: Jul/02/2007 Location: Ottawa, Ont. Status: Offline Points: 6685 |
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Posted: Apr/25/2010 at 10:15am |
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500 HP out of a 390 is doable, but as you push up the HP, the power band tends to rise as well. Since this is mainly a street car, high HP might actually make the car slower because you can't achieve the RPMs required to get that HP. I would forget the HP target and build for low end torque. That is what will make your AMX a screamer on the street.
3" exhaust to the rear in an AMX is near impossible. There is not a lot of room for the tailpipe around the diff. Conventional wisdom says 2 1/4 to 2 1/2" is the limit for the tailpipes. |
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69 Javelin SST BBO 390 T10
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forest
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Posted: Apr/25/2010 at 11:00am |
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wiseco make a VERY nice AMC piston.... flatop, low tension rings, K1 has a goodlooking forged rod, bushed already, and stronger than stock rods, Crower, being as I am a WD distributor for them, will offer whatever you want, I can get custom roller lifters made with plenty of roller shrouding so as to not bleed off oil pressure due to the high lobe lift on the camshaft.
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setting guys out by car lengths....
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pcking
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Joined: Nov/06/2009 Location: W. Babylon, NY Status: Offline Points: 8 |
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Posted: Apr/25/2010 at 11:04am |
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Thanks for your replies, I appreciate the insights. Here are some answers to the questions you posed.
I would want to make it pump gas capable as I plan to put miles on the car - I love my race cars, but they only get driven at the track, so they end up being more like abused trailer queens and the last thing I want is another car I cannot use regularly. I want this car to get driven and race gas prices and limited availability would kill that. I am open to running 93 with some octane boost - but I'm not into running NOS on the street. Would consider supercharging or turbo, but feels very out of place on a car like this, so I'd prefer to push the limits of good pump gas. Also, I live on Long Island, so we're about 110 feet about sea level and have some of the most oxygen rich air in the country (reason why cars always seem to run just a bit faster at Englishtown out in NJ). And as for the 500 HP it is really about 500 HP and 500 TQ or maybe 450 HP and 550 TQ as I agree that the torque number is routinely more important for a street car. After driving late model cars with 400+ HP & TQ, I feel that the AMX needs to be just a bit more potent, but not at the cost of being too radical. I realize that certain concessions have to be made and that I may be limiting myself, but I'd like to try to use the stock block, crank, and rods and add the proper pistons, and build the upper end to maximize the power. If I need to fall a bit short of my target to ensure I can use more of the stock components, I am OK with that, at least to an extent. For example, I'd rather bush and retrofit my rods with cap screws then buy new rods even if it means additional cost over an aftermarket rod. The car is so original that I feel compelled to re-use the factory parts wherever possible and correct any deficiencies, even if it means doing more mods and spending some extra dollars along the way. Appreciate the tips on oiling - I've had issues with having too much oil in the top end in the past and have used some of the tips suggested, such as enlarging the drain holes and even limiting the oil flow to ensure proper oiling, but avoid filling the heads and lifter valley and then starving the mains. I hear the Bulltear front cover and a good 7 qt pan are keys - wondering if anyone makes a T-style pan with the trap doors to ensure consistent oil delivery under cornering loads. This was a big issue with my Mustang Road Race cars and it was corrected with a Canton pan that has about 1 quart of extra capacity on each side to allow for sustained high-G cornering without starvation. Surprised that no-one came after me about the idea of using Chevy 400 pistons - expected to get lynched for that one!!! I was looking at using a flyweight piston from Arias or others and then creating the proper valve reliefs. I know this might seem counter to my previous statements, but the way I look at it there are no NOS AMC pistons, so anything I put in there is aftermarket and I'm more interested performance, longevity and value then about which style slug to use. Also curious about the limits of the stocks 68-69 heads - anyone done any testing to determine how well they can flow? What about updating to SS/AMX specs and porting and polishing and matching to the intake? Or maybe an oversize exhaust valve to help the smaller ports get better efficiency and then sticking with a stock size intake valve to keep the velocity up? Or any know porting experts that can squeeze out every last bit of potential from the heads? As for the valve train I was thinking of a roller setup - appears that Crane makes a popular lifter for AMC that works well up to .600 lift which is likely more than I need for a street engine and using a custom cam sounds like a plan to me. Still wondering about intakes - since it is a stick, I am OK with a single plane intake if that is required, but are there fitment issues in terms of getting them to fit under the hood? Since I never had the engine in the car with an intake or carb on it, I have no point of reference for how much clearance I have. Also, like the look of a stock style air cleaner, but willing to abandon that if needed, especially since they seem to go for a small fortune. Stinks that you cannot get 3" pipes out the back - use them on some other cars ('71 Chevelle w/ SBC on NOS, '91 Mustang GT w/ 408W stroker) and the tone is so distinct and deep that I crave it. Has anyone done an X-Pipe with side exit exhaust? I have fabricated some custom tips that look like NASCAR exhaust in for one of my other cars and they look spectacular - maybe the AMX would like that better? Keep the suggestions coming and tell me if I am way out of whack on any of this stuff. I'm all about doing my homework and getting it right on paper before starting the process. I've rushed projects in the past and the results were lots of hidden costs and lackluster results and I simply refuse to do that to my beloved AMX. |
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amx39068
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Posted: Apr/25/2010 at 11:43am |
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NP with a Torker fitting but the stock air cleaner is a no go for 68/69 due to the smaller neck size. What I do is grab a later model stock style aircleaner with the bigger neck size and put the eariler snorkel on it and if I didn't tell anyone they would never know it is different the stock setup.
The early heads are about 20-30% less efficient than later heads due to the floor design which was changed in 1970 along with the dogleg port design to go along with the new floor. If you want to get bigher HP numbers they are the way to go and you can get Super Comps from Summit or Jegs that will fit your car perfectly. An alternative way to go is to use a flat top style piston with enlarged valve reliefs and the later big chamber heads opened up to 64cc so you can get the ping resistant flat top design with the majority of combustion taking place in the chambers rather than in the hole and the chamber.
The problem with the 68/69 design is that stock the pistons are .045 in the hole and when adding a .045 stock head gasket, you get a relatively large .090 quench which is not friendly to today's pump gas. If you use the 401 crank and custom pistons you can get rid of the issue of being too deep in the hole and when combined with later model heads opened up to 64cc can be very compatible with pump gas depending on the cam and how much valve relief you put in the top of the piston
Jim Landis, aka hurst390 on the forum, makes or at least offers some really nice headers with very big tubes.
The SS AMX cars, which came out in 69 conincidently, used the style heads you have and with being porting and polished along with big valves all made up by Crane, produced some great power but they also used 12.2:1 compression IIRC so again, compression makes power so it depends on what you want to do.
Most folks who use Chevy pistons also use Chevy aftermarket rods in order to get the benefit of free floaters and stronger bottom end that come stock with the aftermaket rods. As I understand it, there is some additional machine work on the crank required when using afermarket rods so I just go with stock rods with new ARP rod bolts which should be fine for a street engine and because I prefer not to modify the crank. For racing, aftermarket rods are normally considered a must.
There is considerable disagreement on this forum about tight quench and high compression with a custom grind cam that creates an acceptable dynamic compression for pump gas so Forest and I are building an engine to test the tight quench theory in real life. We are using a 69 block, 401 crank, the custom Wiseco low tension ring pistons he described that I had Wiseco make specifically for this enigne build, custom Crower solid cam of Forest and Crower's design and new Crower 1.7 stainless roller rockers. The intent of that engine build is to be way over 500 HP and still run on pump gas. It should be done within the next couple of weeks and then will be bench dynod and tuned prior to going into one of my cars and then chassis dyno'd and tuned.
We are hoping to do a shoot out with the engine against Steve Keown's killer AMX engine but our timing may not have the engine finished in time before Steve reworks his current engine so we are doing our best to get our engine down to his dyno guy before he decides to rework it. I am keeping my fingers crossed that we will be done in time to make it happen.
I've done 1/2 dozen or more 450-500 HP engines in the last couple of yeares with mostly stock AMC parts other than pistons and valve trains and others have done some really strong builds with some additional aftermarket parts as well.
I know from speaking with Nick Alfano, he recently did a 70 390 with AMC steel heads for a guy with a Rebel Machine and it pumped out well over 500 HP and well over 550 lb ft of torque and runs on pump gas using Nick custom designed pistons so it can be done.
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Dan Curtis-Owner and CEO AZ AMC Restorations; Facebook: https://www.facebook.com/amcmusclecars/ & Curtis Real Estate Development
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forest
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Posted: Apr/25/2010 at 12:16pm |
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I have already tested the tight quench and wicked high compression for the past 5-6 years.... works just fine. Makes a BUNCH of power. Dans engine with be one bad mofo when its done... wait a little while longer, you will get some more opinions on how to setup your motor, choose what ideas you like best and good luck!!
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setting guys out by car lengths....
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bigbad69
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Posted: Apr/25/2010 at 2:34pm |
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69 Javelin SST BBO 390 T10
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firecapt321
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Posted: Apr/25/2010 at 5:45pm |
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If you have money, which you obviously do, you need to just pic up the phone and call Barry Allen Race Engines in WV, tell him you want and all iron 500 plus HP and TQ street motor, send him your cores and wholla.... you will get a dyno tested and proved ready to drop in motor for probably about the same as your gonna spend attempting it and not making it, unless you have a machine shop handy and get super friendly prices on a lot of port work etc etc....
If not, you need to pic up the phone and contact one of the few guys that have built several 500 + HP and TQ AMC engines... ITs not super duper hard, but not easy by any means, there are a lot of guys out there that think they can throw on some 291 heads, torker, and a holley and pump out 500 HP in their brain dyno... You really really really need to call one of these guys... Barry Allen, Hemmy Adkins, Roger Mayes, Nick Alfano, Ken Parkman or a few others...... and dont confuse yourself by asking everyone what you should do and how to get there and get 500 different opinions.... cause there are a ton of people on forums like me, that dont know a thing about true performance engine building, but will try and reply like they do... and that goes for any car forum, just not this one, so dont people go taking that personally not entirely directed at this place... Edited by firecapt321 - Apr/25/2010 at 5:48pm |
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pcking wrote: