straight up.

what makes your cam larger than mine? you keep saying my cam is small. mine is a 232/240 and yours is a 238/240. the major differences are the LSA and you have it retarded 4*. i agree than with it being advanced it's going to have less peak hp. and with a 117 LSA it's going to have less peak torque and possibly overall. but to say my cam is small, especially when you are running the almost same duration, i just don't get. you made 530 rwhp with your 'small' cam.

i am not talking peak numbers. i'm looking at each lift point on the heads and seeing an average of 25-30 cfm of flow. if the exhaust side is backing up the flow, then i'm all for changing heads. i've already looked into the patriot and AFR heads. called tony mamo and had a small conversation about it.

ok found the patriot LS6 heads. it's on their new products page even less than 25 cfm on the exhaust side average. 227 cfm intake for patriot and 224 cc runner on mine.

lift -------- p i/e ----------- m i/e ------ diff
.100 ------ 79/81 ---------- n/a
.200 ------ 145/120 ------- 145/109 --- 0/+11
.300 ------ 204/164 ------- 209/148 --- -5/+16
.400 ------ 251/191 ------- 253/174 --- -2/+17
.500 ------ 282/206 ------- 288/181 --- -6/+14
.600 ------ 300/214 ------- 301/205 --- -1/+9


yeah, yeah every flow bench is different. who's is right? i just can't see spending $1100 for heads that just don't flow any better than mine. their LS6 STYLE heads flow better than their actual LS6 heads.

a low peak and not carrying through the rpms doesn't only mean theres a restriction in the set up. i'm thinking more of a valve train issue. looking into the valve train issue as we speak.

another thing. after 6000 rpms, the knock sensors go off to the tune of 4* retard, according to my HPTuners. this is with 26* and 21* of timing. so that tells me it's not real. this is pointing me towards valvetrain still.

the MAP readings after 6000 rpms were fluctuating at 94-95 kPa. now, with the engine off the kPA reading is at 102 kPA. so, maybe there is a restriction, but that would be somewhere before the heads. is it the SLP airlid, the ported MAF ends not large enough, the 85mm NX TB not large enough?

not going to say the heads aren't hurting airflow. i've always had that in the back of my mind. especially that GTO with the 224/224 and AFR 205 heads that made 450 rwhp.

as far as the intake itself, i don't have any flow numbers on it. so, i can't say if a FAST 90 would do any better. it's a special intake that NX designed to compliment the NXL direct port nitrous system. there are no nozzles. the intake is drilled to be the nozzle. last italked with NX, there were only 5 other manifolds out in the world being used. they had 12 made. here's what that looks like:

http://www.stealthram.com/familypics...esonintake.jpg

i am very impressed with your 530 rwhp motor. gives me something to ponder. with the only main difference being retarded and having less LSA, i would point more towards the cam as being my issue for not having as much power. then again, i need to deal with the valvetrain issue first.

don't think that i do not appreciate your opinions. i really do. as i said, if i didn't want criticizm, i would never have posted. keep the ideas coming.

 

You may think that isn't a "small" cam, but to most of your stroker-peers, it is. My little 383 uses a COMP XER244. I'll bet that GTO would make over 500rwhp with a bigger cam, so I'm not sure what the point is...

You don't know what rwtq you have on the squeeze, but I'd wager that I'm right there. Again, no bravado, just pointing out that you have 25 more c.i. and 100HP bigger shot (DP too!) and aren't making more power than me. That's why I think you have room to improve.

If you are happy with it, that's all that matters. We are just suggesting that since you went to all this trouble, why not get everything you can within reason? A good, patient tuner (like Mike) can make a hairy engine daily-drivable...

 

point being is both of you keep telling me i need a bigger cam. the gto made more rwhp than me and a much smaller cam. plus kraest's cam is a 238/240 and mine is a 232/240. so i keep wondering why you two keep telling me i need a bigger cam. maybe a different profile, but not a larger one. after all kraest made 90 rwhp more than me with only 6* more on the intake side.

using my na numbers as being square, my assumption would be in the 650 rwtq range. i gained 225 rwhp on the nitrous. but, it's nothing more than a guess.

am i happy i made 663 rwhp, sure. i was hoping for more on motor than what it did. there are issues that need to be addressed. i am self tuning as well. and i'm nothing special in that area. i've been tuning since april on this motor. never tuned an LS1 before. so i jumped head first into something huge.

i appreciate the suggestions. gives me something to ponder on.

 

6 degrees of duration @ .050" can make a huge difference and pick up a ton of power if the cam is already small (and yes... mine was on the small side as well.) It's really not in your best interest to put anything less than a 24x duration cam in a 400+ cube motor if you want to make power. Mine was retarded a total of 8 degrees since it was ground on a +4 and would up being on a -4. That's one of the main reasons my setup made power like it did despite the smaller cam. If it was on a +4, it would have peaked very early like your car did. The 110 vs the 117 LSA is going to be another huge factor on NA power. There's absolutely no reason to put that kind of cam in there if you aren't running a blower. 112 would have been enough for a nitrous application or a 114 at the absolute most... you're not making positive manifold pressure with nitrous.

I'm not talking about peak numbers. I'm talking about flow numbers in general. They can all be adjusted to what they want them to be.

It all depends on who you talk to. You can see how well the heads have been worked by the power you produce. Having high flow numbers doesn't mean that a head has great port velocity -- I've seen plenty of 300 cfm heads that weren't worth a **** because they got very turbulent and messy and were simply "hogged out" to achieve "flow numbers." On the other hand, I've seen "true" 270cfm heads that would outperform those trash 300cfm heads any day of the week.


My 408's valvetrain sounded like a bag of marbles and the knock sensor agreed. I picked up around 15-20rwhp on the dyno by simply having Allan desensitize them.

I was using the LS2 TB and the stock Corvette MAF with a Haltech Stinger/Vararam combo. I don't think that's your problem. Obviously you'll make a tiny bit more power by taking off the air cleaner, but do you really want to?


AFR has spent tens of thousands of dollars designing their heads. I've seen those heads make some really great numbers, but they are very pricey.

Your manifold looks awesome. However, I don't know how it will perform for an NA application I'm sure it needs to be port-matched to the heads if it hasn't been already.


Good luck in your quest

 

Let more air out??? Why do you keep insisting that exhaust flow isn't important? There's more to making power than just getting air into the cylinders. You have to get the exhaust out fast enough to let a full intake charge in. If your exhaust is choked then you can do anything you want to the intake side without gaining a single HP.
This can be bandaided somewhat by more overlap and more exhaust duration.

 

i never said it wasn't important. i said what will another 25-30 cfm of flow do for me. exhaust is under high pressure as it is. if i can get another 90+ rwhp by changing heads and cam, i'm all for it. but, if all i get is 40 rwhp, i'm not interested in spending $3000 for only a small to moderate gain.

kraest, you've been a great help.

 

No problem.

I'd start by retarding your cam 5 degrees and see what happens.

Are you running the Cometic .040" gaskets? These motors like compression in the low 12s on 93 octane.

See what retarding the cam does. If it makes a big difference, you might want to go back to the drawing board and swap to a different cam.

As far as heads go:
Unfortunately I no longer see the heads that I had on my car on Patriot's site. The only REAL LS6 (243 casting) head they offer appears to be a 227cc 2.00/1.55 valve that flows around 300/213 peak cfm @ .600 on a 3.905" bore. That's a FAR cry from my 2.02/1.60 240cc that flowed somewhere in the low 330s @ .600"

Mike

 

unfortunately, i cannot use MLS gaskets with these heads. they have the service notch on the deck surface.

 

at the suggestion of a member of kraest, he said to retard the cam to make more power as his opinion is the cam being ground 5* advanced is limiting my peak hp at 5700 rpms. well, it didn't go as planned.

blue line = straight up
red line = 5* retard

 

I think it is interesting how much of a change it made. What about going the other way 5deg?

 

extrapolating from what just happened, the guess would be a gain of the same amount. but the cam is already ground 5* advanced to begin with. but, i don't see that happening. looks like the homework on the design of the cam was already done.

 

That's completely ridiculous. Damn. Was that with the converter locked? How much did you retard the cam?

BTW, your A/F is getting lean on that dyno run compared to the previous one. Should have added more fuel.

Well, it looks like the heads are to blame. There should be NO reason that the graph did that when you retarded the cam. The power is still crapping out before 6000 rpm and falling too quickly -- very similar to my buddy's 205cc Dart heads on his 383 LS1.

I still say that the cam is too small and the heads don't flow enough air for that big cube motor. It's sad that even retarding the cam couldn't buy you some power.

 

converter locked. as stated, in the post, i retarded it 5*.

only made one pull with same tune as the other pulls. i'll just put the cam back where it was. took me just under an hour to pull the front off and change the degree setting on the timing chain.


i agree on the heads, especially after this. i figured they would hold me back, but not this much. still have to figure out the drop in the 6k range. i keep being told it's valve float. with 3/8" pushrods and shaft mount rockers, and the latest crane 833 springs, i'm at a loss there. unless the spring setup isn't working out. might need to increase pressure.

 

I think it's a combination of both the cam and the heads, but leaning more towards the heads. I doubt it's valve float with those springs -- They appear to be pretty decent.

I ran stock rockers and Patriot Golds on my 408. No problems with valve float even with the rev limiter set at 7200 rpm.

Mike

 

If your up for a little more experimentation. Throw in a set of hardened stock dia. pushrods and your stock rockers and see if the ''valve float'' goes away.