Getting the most power out of my 400 stage 6 heads

[chrisd426]

My biggest thing with this at the moment is picking the right size cam, sorry about writing a book but it has some points so bear with me here I picked this 400 up a while back as a "running engine" for a cheap price, the guy pulled it out of his super bee charger to put a 440 in, he got the car with the engine in it and didn't know anything about it. My original plan was to check it out, if I liked what I seen inside, throw it in the car to get it running but of course I wanted to pull the oil pan and heads to see what I had "I needed to to put the proper oil pan on anyway", which before I put an engine in something i don't know the background on I like to check it out anyway. Make sure it's all good. Well someone before me either loosened or didn't tighten the intake bolts well and it was actually missing a bolt on each side and the 906s burned a few valve seats out... Otherwise engine was perfect and clean enough to eat off of.. The engine is either very low miles or someone freshened it up, it's still standard bore so I'm assuming its stock Pistons, but they aren't as far down the hole as smogger 440s I've pulled apart theyre about .075-.080 down. bearings are in really good shape and I can still see hone marks in the cylinders. Someone tapped the oil pickup for 1/2" hemi size pickup, it had a 509 purple shaft and a Holley single plane street dominator intake, 7qt oil pan, 906 heads with valve work and mild porting and regular thick paper type head gaskets.
I'm thinking the motor may have been balanced, the crank counterweights have a good bit of metal drilled out and on the rod caps they don't have numbers stamped on them like most machine shops do that I can see but it has different symbols on each rod and rod cap like clover leaf, spade, diamonds, symbols like a deck of cards I've never seen that before...

Now onto The details of my car 72 dart, fiberglass hood, trunk pan is gone so I'll probably be replacing with aluminum, or would that hurt traction too much? I may gut the trunk lid. 8.75 rear, 3.91 sure grip, previous owner had new super stock springs, relocate kit, pinion snubber, mini tubbed, aftermarket torsion bars, aftermarket manual steering box, manual brakes, disc conversion in front, installed I'll be installing frame connectors, and a cage, i have a 12 point cage but I may just make it a 6 point for now if it breaks the track required e.t. I may try to keep the back seat, because my 5 year old daughter already told me I need the back seat so she can ride in it lol I'm putting in lighter weight front seats. (Originals are long gone I'll be running 10.5 or 12" slicks or drag radials. Probably a 28" or so tall. Car will be a bracket car a couple weekends a month, they run 1/8th and 1/4 mile at the track, 1/8th on weekends so I'll probably be running that more often than 1/4 but I'll also drive around town a little to pick up chicks (joking) and to have a little fun with the ls guys around here. And drive to the local cruise in... I have a good cooling system, Griffin radiator, 440 source hi flow pump and alum housing, plastic flex fan and maybe an electric fan on the front of radiator as well..
I have a set of stage 6 heads, 68cc chamber so with 20+cc less than the stock heads its bumping the compression to 9.39 with a felpro gasket, 9.89 with a steel shim gasket, can steal shim gaskets be used with alum heads? Heads were done by David porter They've been modified for external oiling so the original oil ports between the intake ports were blocked off to allow more porting and also is suppose to improve top end oiling, it uses the external lines that feed from the oil plug at the back of the block like the Indy heads. and have epoxy in parts of the ports so they were done quiet nicely. Which in the future when funds allow I plan on stroking the 400 and putting the heads to good use, but for now a stroker isn't in the budget. And I don't have any other heads and I figure these will help compression and a lot more flow over any factory head and I already have them sitting there waiting to be bolted on. I have 3 converters on my shelf to choose from, one is a tci 26-2800, I have a 3,000-3300, and a 35-3700ish
Now my first thing is a camshaft grind that I can run with the flat top no valve relief Pistons, I know with them being a little down in the hole that will act somewhat as a valve relief. What's the most lift I can get away with? But I know duration and lsa effects that more than lift, Wjen the intake valve is at full lift the piston is down on the stroke, so nowhere near the piston. I don't want to over Cam the engine being they say the low decks are easy to overcam, but I think that's more with street engines and stock type heads? Which with no valve reliefs I know I won't be able to run a monster fan anyway I'm thinking a 110lsa? I do want a nice wide power band, not just a bunch of power at one rpm. im looking at comp cams, and oh yeah flat tappet, not a roller. For one comp seems to make good cams for mopar from what I've seen and I have a buddy that works at a parts store in town so I can get them at a significant discount, much less than anyone online or summit etc. I think he could get other name brands as well. I was wondering about the Comp high lift .525 or .545? Or something in the extreme energy line? There so many choices out there and so many factors here with what I can run without putting a valve thru a piston... Also I don't want one that will cause me to lose a lot of compression, if anything maybe help it.
Now onto intake I'm thinking an rb intake would be better because of the longer intake runners would help the torque, keep in mind the stage 6 heads use spacers that bolt to the head, not cast-in like a lot of newer heads so with a low deck you can run an rb intake or a b intake with spacers. For rb engines I have a torker 2, and a performer Rpm, the rpm has had plenum work with the center divider cut down, and beveled, and also the short turns worked, torker 2 has plenum work. For low deck I have a eddy tm6 with port matching and a Holley street dominator with plenum work and porting, but with whichever intake I run I'll have a deep port match to the heads of course im thinking the torker2 maybe? I'm wanting to try to get my dart into 11s, maybe high 10s if possible, and I also have a couple n20 kits laying around so putting a small shot on it will maybe happen to get it there... I've seen guys put similar heads on 383s before so why can't I do it with a 400?

 

[Abodybomber]

Pictures,would help.. Do you have a goal,other than spending too much moolah? Damn,you gotta lot of choices,what do you want it do ?

 

[IQ52]

A well worked Stage VI head at 68cc has probably been milled quite a bit, so the valves are going to be even closer to the pistons than with a stock head. You are going to have to put a cam in the engine and test the piston to valve clearance. Why not test the clearance with the existing 509 first, using the STG VI heads, and see what you have to work with? Bolt the valve train and everything up and measure the clearance. That's what we do at the shop. You have too many variables to say from here, "Yep, them pieces are gunna work!"

 

[AndyF]

I agree. Get the engine up on an engine stand and start trying things. You probably can't run a very big cam without valve reliefs but you'll just have to check it to see. The Performer RPM is probably the best intake for that engine.

 

[chrisd426]

A well worked Stage VI head at 68cc has probably been milled quite a bit, so the valves are going to be even closer to the pistons than with a stock head. You are going to have to put a cam in the engine and test the piston to valve clearance. Why not test the clearance with the existing 509 first, using the STG VI heads, and see what you have to work with? Bolt the valve train and everything up and measure the clearance. That's what we do at the shop. You have too many variables to say from here, "Yep, them pieces are gunna work!"

Well the 509 is what I pulled out the engine so I know it clears. I know once I buy a cam and get the pushrods and everything for it I'll of course bolt heads on, use some putty and check clearence on top of the Pistons I just want a ball park idea of what is enough to make the most power possible without it being too much because it would suck to spend a couple hundred bucks on a cam&lifter set then it not clear pistons and be Stuck with a cam I can't use nor return because it's been installed...

 

[chrisd426]

Pictures,would help.. Do you have a goal,other than spending too much moolah? Damn,you gotta lot of choices,what do you want it do ?

Like I said get the most power out the engine I can with what I got, really not spending a lot of dough, most of everything I have is stuff I've got laying around, I've pulled off other engines and cars, or traded for, a while back when I was looking at buying heads I was planning on getting a set of stealth heads it's what I had the $$ saved up for and found these stage 6 heads ready to bolt on with extras for the same price so I went that route and figured once I build my stroker they would be a lot better than the stealth heads dollar for dollar

 

[IQ52]

Well the 509 is what I pulled out the engine so I know it clears. I know once I buy a cam and get the pushrods and everything for it I'll of course bolt heads on, use some putty and check clearence on top of the Pistons I just want a ball park idea of what is enough to make the most power possible without it being too much because it would suck to spend a couple hundred bucks on a cam&lifter set then it not clear pistons and be Stuck with a cam I can't use nor return because it's been installed...

OF COURSE IT CLEARS WITH THE 906 HEADS, BUT DOES IT CLEAR WITH THE STG VI HEADS. THAT IS WHY YOU TEST IT WITH THE STG VI HEADS AND 509 YOU HAVE SO YOU GET AN IDEA OF HOW MUCH ROOM YOU DO HAVE RIGHT NOW WITH WHAT YOU'VE GOT. Yes I am yelling. I have been on the road for four days and I'm tired and short tempered. You've got the STG VI heads and the 509. Set them up and test the piston to valve clearance you have right now. Then we can give you an educated guess and not a dumb luck guess.

 

[chrisd426]

Ah ok I got you now, I was just thinking I'd have to order a set of pushrods and all for a cam I'm planning on throwing away, which honestly I don't even know where the 509 is at the moment, I've been In the process of moving since me and my ex split up it may still be in the shed at my old house.. But if I do get it I guess I could use the pushrod length checker as a pushrod to check valve clearances I didn't really think about changing heads would effect it tHat much but I guess with a little bigger valve it could make a difference, and also being I'm putting my Harland sharp true 1.5 rockers on vs the stock rockers which they say aren't a true 1.5 but actually less can also effect it which I forgot to mention the 906s I pulled off it had the crap shaved out of them, comparing them to an uncut pair of heads that came off my 440, they were dang near shaved down to being a closed chamber lol, not much of the meat left on the open part. I don't remember now exactly what I'd cc'd them at but I want to say the 906s were cut down to an 80-82cc. an above comment said that my stage 6 heads have probably had a lot of milling done to them, I don't think they have, from the specs I've looked at of stage 6 heads for sale online in stock form, they have a 75 or 78cc chamber, so would it really take that much milling on such a tight quench chamber to cut off 8-10cc? I'm sorry I have so many questions I've never had this situation, I've never thought about putting a big cam in a no valve-relief engine before, also I've not messed with many big blocks, I grew up with small blocks and this will be my first engine I've dealt with that had adjustable shaft rockers, we either had stock shaft rockers, or magnum style or stud mount rockers. There are some things I know more about with engines but valve train geometry is one area I'm a little less educated on. Doesn't Valve lash reduce or increase lift and duration? Also isn't the intake valve at full lift when the piston is on the down stroke and at bdc? And isn't the exhaust valve full lift on the up stroke and at Tdc? Also wouldn't a wider lsa be more forgiving on valve relief than a smaller lsa? Like say for example wouldnt a 114 lsa 509 be less likely to hit a piston than a 108? I've done some google searching on the subject and one guy was saying he had a 400 with the .528 purple cam with 1.6 rockers, but the .528 also has a 112lsa and smaller duration, doesn't it? I guess the main question should've been what's the biggest cam that someone has used on stock type Pistons, but I know what may clear in one engine may not in another, I'm just trying to get an idea of what I need to look at, I know with theSe heads I'm handicapping the potentionial with a small lift and small cubes which I'm saving up to get a stroker kit, but that'll be a ways off, but for now I'm trying to get my car running for an event in October and also want to get back on the race track... I've been off the track for about 8 years now... But being I don't have the ex ole lady now which the night we met I was in the process of putting a 500ci stroker into my roadrunner, but when I got involve with her, we ended up having a daughter, and I sold my stroker and ended up putting cars on hold, I'm regretting selling that 500 now because I'd be putting these heads to good use on it now, it had iron heads 2.20/1.81 valves, full port 906s on it, anyway, I think with the 400, i think these heads will flow plenty well enough with a .500ish lift to feed it, and I think it will probably want to pull past a safe redline, which there's guys out there says oh I've revved stock 383s and 400s to 8 grand before, but I don't want to do that, I want it to live and see that stroker crank in the future... What's a safe rev limit for the bottom end on this motor?

 

[chrisd426]

Flow numbers for these heads with 2" exhaust pipe lift range .100-.600
.100 .200 .300 .400
67/56 142/107 204/156 253/198
.500 .600
287/233 307/257.

I for some reason was thinking I'd need a lot or lift and this and that, though more lift would mean more flow, but is it safe to say with a .500-.520 lift and flow in the .290 range it would feed that 400 just fine, probably more flow than the engine could use, at least until wide open throttle but like I said this is going to see the drag strip every other weekend or so, I'm probably the first person to put stage 6 ported heads on a stock stoke low Deck, but what the heck? Now from what I've saw with my research is it's easy to overcam a 400 on duration, and around .240-.250 range is the most you want, more than that and you actually lose horsepower now I think that's referring to stock head, and more street driven cars, but the principle is still the same right?? I'm thinking something in the .240-.248 range, and a 110lsa? Another thing I forgot to ask about is not losing too much cylinder pressure/compression, some say a wider lsa keeps you from losing as much pressure, but the whiplash cams that are supposed to be for low compression engines and make more compression have 107lsa, which the comp thumper cams have a grind that is almost identical to the whiplash but if one wants to run nitrous doesn't he want a wide lsa? At least that's what a buddy that's building a turbo/nitrous ls camaro was telling me earlier, but I'm only wanting to run a 100 shot if I need it... I'm expecting I should run 11s as with a big block a body with high flowing heads it shouldn't be too much to ask, but I would like to dip into a 10, and I've got 2 sets of solenoids, 2 bottles, lines, jets, fogger nozzles and a plate, but I'm wanting to remain sleeper mode so if I do run spray I'll probably plumb one of the fogger nozzles into the bottom of the intake with a small 100 shot, which once I build the stroker and have all forged, h beams, girdle, and cross bolt caps that'll probably be 2 stages, a small shot on launch, and a big shot on the second... And yea I already know I'll be able to pick any right can I want with that because I'll have those luxury of valve reliefs and it'll probably be a roller... Which I originally planned on dropping my 440 in the dart but when I picked up this 400, I figured I'd stroke the 400 in the future being its the stronger/lighter block, and a good candidate for it. so I'm keeping the 440 fresh, and once it's finished I'll sell it and buy the bottom end for my 400 block...

 

[famous bob]

Flow numbers for these heads with 2" exhaust pipe lift range .100-.600
.100 .200 .300 .400
67/56 142/107 204/156 253/198
.500 .600
287/233 307/257.

I for some reason was thinking I'd need a lot or lift and this and that, though more lift would mean more flow, but is it safe to say with a .500-.520 lift and flow in the .290 range it would feed that 400 just fine, probably more flow than the engine could use, at least until wide open throttle but like I said this is going to see the drag strip every other weekend or so, I'm probably the first person to put stage 6 ported heads on a stock stoke low Deck, but what the heck? Now from what I've saw with my research is it's easy to overcam a 400 on duration, and around .240-.250 range is the most you want, more than that and you actually lose horsepower now I think that's referring to stock head, and more street driven cars, but the principle is still the same right?? I'm thinking something in the .240-.248 range, and a 110lsa? Another thing I forgot to ask about is not losing too much cylinder pressure/compression, some say a wider lsa keeps you from losing as much pressure, but the whiplash cams that are supposed to be for low compression engines and make more compression have 107lsa, which the comp thumper cams have a grind that is almost identical to the whiplash but if one wants to run nitrous doesn't he want a wide lsa? At least that's what a buddy that's building a turbo/nitrous ls camaro was telling me earlier, but I'm only wanting to run a 100 shot if I need it... I'm expecting I should run 11s as with a big block a body with high flowing heads it shouldn't be too much to ask, but I would like to dip into a 10, and I've got 2 sets of solenoids, 2 bottles, lines, jets, fogger nozzles and a plate, but I'm wanting to remain sleeper mode so if I do run spray I'll probably plumb one of the fogger nozzles into the bottom of the intake with a small 100 shot, which once I build the stroker and have all forged, h beams, girdle, and cross bolt caps that'll probably be 2 stages, a small shot on launch, and a big shot on the second... And yea I already know I'll be able to pick any right can I want with that because I'll have those luxury of valve reliefs and it'll probably be a roller... Which I originally planned on dropping my 440 in the dart but when I picked up this 400, I figured I'd stroke the 400 in the future being its the stronger/lighter block, and a good candidate for it. so I'm keeping the 440 fresh, and once it's finished I'll sell it and buy the bottom end for my 400 block...

I got a tired of reading all this: I think I`d buy a set of (or have them made) 1,- pistons, or2,- rods to get some quench in that thing, and at least get it up to 10 something c.r. !

 

[bOb shingler]

I just couldn't finish reading all of it. take the pistons out and see if they are stock or after market. if stock toss 'em out, it after market go have valve reliefs cut into them. It's not that hard to do.

 

[IQ52]

I've had STG VI heads here that after having been worked are in the 90+cc range. 10cc's on a small chamber head is about .065". This reduces the P-to-V clearance the same amount.

If you have two cams with the same lift and duration but having different lobe separations, the one with the wider lobe separation will close the intake valve later and reduce cylinder pressure. Piston to valve clearance is measured during the overlap phase when the piston is close to TDC. Yes wider lobe separation is more forgiving on piston to valve clearance.

You want to have someone tell you what cam they ran in their engine and guess if that will work in yours. Okay.....I've run an old .600" lift solid roller, 280/280 @ .050" on a 105 degree lobe separation in a low compression 383 with 906 heads. However, I did measure the piston to valve clearance and cut valve reliefs in the stock cast pistons. Results? 525 HP.

So then it sounds like your plan is to measure nothing and hope another's cam will fit. I say put any cam in there you want to run and fire it up to see if anything bends. If nothing breaks you are good to go. Best of luck.