gols1go

iTrader: (4)

A buddy of mine is trying to decide whether to put the L92 heads or the 317's on his soon to be boosted 370. He has access to both so the problem trying to decide based on cost is not a factor. He's also doing a Holley hi ram intake for either so that's not the issue. He basically wants a good out of boost, super bad in boost car! I personally had a cammed 6L with L92's which was NA but I loved it. Great torque down low and a blast up top. But does anyone have any experience with both heads on the same setup with different results. He also knows that great power can be made with either set, just wanting to know if either is better when you have both sets in front of you. Thanks in advance!

Bob@BruteSpeed

iTrader: (16)

Stock vs stock, the L92's flow much better, way better. Bob

LJMSJohn

And intake port flow is really the last thing to be concerned about when picking heads for a boosted motor, especially if its a turbo car.

Given the intake thats going on it... if he wants the best off boost response ( if its going to be a turbo car) put the 317's on it.

Bob@BruteSpeed

iTrader: (16)

Really? Bob

gols1go

iTrader: (4)

So LJMS believes that the 317's have the best out of boost response. I was confused when I read this. I do understand that the L92's are down 10-15 ft-lbs below 3500-4000 given some cams with the exact same short block. But that's on N/A setups and at 350-450 ft-lbs who is missing the 10-15. Can you really feel 10-15 ft-lb difference at 2500-3500 rpm? Also I would believe that the better flow of the L92 heads up top would equal even more power boosted. I only say that because of the many running ported heads. I do understand that with boost flow is not as important, but is it completely irrelevant. Would it matter on a 5.3 to have the same compression and run a set of 862 over 243's?

Forcefed86

iTrader: (4)

Don't the L92's also have less deck surface, making them more prone to HG seal problems?

gols1go

iTrader: (4)

And let me and that I respect everyone's experience. I am just trying to reason this out in my head. I have only had a cammed 6L with L92 myself that was N/A and now I'm boosting mine too. Never had a cammed 6L with 317's to compare the off boost feeling to. I just built a turbo 5.3 lm7 but with the setup it spools so fast that it's too easy to get into boost so I barely know what out of boost feels like lol! Off boost there is no comparison between the 5.3 to my old 6L setup, but in boost the 5.3 is more than I expected!

ablakez28

iTrader: (9)

I had this concern when I installed mine. I decided to try them since I was given the pair for free with a shortblock I was buying. They even had a fairly large .060 mill job on them.

Last year I ran them on a 408 and probably had around 20-30pulls in the 20-23psi range without issues.

That said if I do happen to spit out a gasket I am probably going to stick some 317s on and see what performance changes there are.

408GT

iTrader: (2)

I have an L92 w/ an S-480, and I've currently been looking into this myself. My combo seems laggy at low rpm. I don't think you can get caught up in the flow numbers when selecting a head for boost. I'm sure N/A the L92 is a good head. The deck seems to be around a 1/2" thick, but I think it's the casting/material that makes them "weak".

Also, the Cathedral port heads have been proven over and over again. Look at Stock48's car. He's doing bottom 8's with 317 heads and a truck intake.

I'd have to agree with LJMS on this one.

408GT

iTrader: (2)

I know the op in this thread is n/a, but there is some good info in there: http://www.yellowbullet.com/forum/sh....php?t=1600370

gols1go

iTrader: (4)

Nice info thanks! Keep this up and he's definitely going to throw on the 317's. I wish someone had back to back runs on a boosted setup with both heads.

Bob@BruteSpeed

iTrader: (16)

We always made a lot more power with any given boost level with L92 heads over 317's with ProChargers. It will be interesting to see more replies. Bob

408GT

iTrader: (2)

So would I. I'm tempted to try it on my combo, but I don't have all the parts lying around to try it. I would probably need to change out my camshaft too if I went with the 317's.

Jasperstang308

lil john told me the only heads that were stronger were the lsa heads and thats only because they are made with a different material. All other heads have the same deck surface. id think a 370 ci motor will make plenty of torque out of boost to put put around town id go with the l92 heads

ablakez28

iTrader: (9)

I have run both but the setup changed too much to be a fair comparison. I dont have dyno numbers but if this helps for comparison. I have not had many clean runs at all on the 408 so it might go a good bit quicker not sure.

SBE LQ4 6.0+317s
TU1.5
S480
9.0 @150 23psi

408 with CNC 823s
LJMS Stage IV
S484
8.8 @153 20psi

MIAmotorsports

317's. You keep going back to N/A numbers, for your argument? Too big of a head and it will be sluggish and harder to make boost down low. On the street you will really notice a difference IMHO with the 317's. The extra intake wont do nothing but hurt you in a lower horse smaller cubic in. street motor and the exhaust flow isnt as pronounced between the two and more than likely wont come into play on a street motor. If you are going to make less than 1000-1200fwhp there is absolutely no need to get a head that flows better than the 317.

M.BOZZ

iTrader: (14)

gnx7

iTrader: (28)

If your buddy wants it responsive down low... then why is he running a Holley Hi-Ram?

I went 163mph on a 100% stock LS3 intake with big turbo. It does have MAST LS3 heads. And shift points are over 7000rpm.

A turbo setup simply won't be as responsive as an n/a car. NEVER. Maybe if you sprayed nitrous.... but the big problem with making big power down low will be actually being able to use it. He can't really have both.

Unless he has boost by gear.... I doubt he will be able to put the power down in 1st or 2nd gear any way.

408GT

iTrader: (2)

This.

Also, the Holley intakes doesn't fit the intake ports very well.
I watched a video on youtube with Tom Nelson talking about people spending a bunch of money on an aftermarket intakes that actually hurt performance. He stated that the stock intakes did very well.

alocker

iTrader: (10)

I run the L92's and even with a small cam it's super soft down low out of boost. I consulted with Jarrett at JFR and he said the 317's are the way to go. It's the same debate from 40 years ago about rectangle port vs oval port. Unless this is an all out race car spinning 7500 rpms I would go 317.