JASON 77

iTrader: (22)

have heard different things here. some say that FI is just that forced. would a higher flowing head be worth while? or can you achieve the same from a set of stock 317's?

ChevyChad

iTrader: (50)

The exhaust part is not forced, and that counts for a LOT!

Camaro01SS4life

iTrader: (4)

I would say its all matter of speculation...But any better flowing head will result in higher gains typically...To answer your question, I would think it would be subjective do to many of factors...Amount of boost, cam etc...I would be more worried about lifting the head with using a higher boost on a stock casting...
I have not come across stock heads against ported heads in a FI dyno comparison...

Kev

Camaro01SS4life

iTrader: (4)

I could see getting better gains with port matching an intake to the runners...

Kev

Photochop

iTrader: (74)

A general rule of thumb is you'll make more power at the same boost level with a ported head vs. a stock casting.

That said, a turbo application is a little more 'forgiving' about a less efficient cylinder head than a supercharged application is.


EDIT: Just saw your other thread. If you're going turbo, the 317s are a great bang for the buck head. Good flow characteristics out of the box, and they lower your compression pretty effectively due to the larger combustion chambers. You need to consider how much power you're wanting to make ultimately because some have seen the 317s not last too 'reliably' (compared to a thick deck AFR/ETP etc head) at above 600-800rwhp (wide range I know, but this differs depending on who you talk to, FWIW). Couple things to help with this are obviously better springs, studs, good gaskets, and making sure your tune is dead on.

JASON 77

iTrader: (22)

lookin into a T70 .96 or a T76 .96. it is a stock lower end, no more than 12#'s boost. lookin into a cam, something kinda similiar to what EPP has. i know some one that has a set of 72cc heads that flow 314 on stock castings, big valves. just tryin to figure this turbo setup out. I AM NEW TO TURBO's so excuse my questions.

Photochop

iTrader: (74)

dont worry about it man. i'd personally go 76, this 70 I've got is choking the car at higher RPMs at 15psi.

MelScrilla

iTrader: (2)

+1 on that, thats why the heavy hitters all run aftermarket heads. If your not looking for bragging rights on the dyno 317's will get the job done, I've been told they're good up to about 800rwhp. That being said it would be easier to make those numbers with aftermarket heads.

gold98Z28

iTrader: (7)

sure you can crank the boost up and make the same power thru a stock head to a point. but your putting more stress on everything in the process to make the same power as you could on less boost and more head. like everyone said. more power to be had at the same boost level with a better head

DeltaT

iTrader: (5)

Ported heads makes your engine a more efficient air pump and will pay off whether that air is ambient pressure (NA) or force fed. If you put a ported head on a previously good running motor, with no other changes, the boost should go down and the power should go up. Boost is only a measure of restriction - how much air is left over that your motor can't swallow (pump). Believe it or not the intake side porting actually is more important, because it allows you to cram more aire into your cylinder where it can be fueled and made to perform work.

Jim

396375

iTrader: (10)

With a stock bottom end the 317s will give you all you need.Aftermarket heads will really shine once you move up to a forged motor.I'd hate to see you put expensive heads on a stock bottom end and blow the motor taking the heads with it.
Good luck.

ninetres

iTrader: (35)

Yes..

stevieturbo

The heads are generally the most restrictive part of an engine.


So you figure out if they are important or not.

shawn_c992001

This is going to be my set-up after this winter. ARP2000 rod bolts, possibly forged rods and pistons if I can swing it in the budget, P&P 317's, Thunder's LS2 Cheater cam, LS7 lifters, Extreme springs, Comp push rods, and a Walbro 255, BAP, and boost Ref. regulator. Shooting for 600+rwhp.

black01_WS6

iTrader: (13)

I would put the 317's on to make sure everything is running correct- then later down the road turn up the wick and throw better heads on.

You can pick up 317's cheap- run them for a year and sell them for the same amount you paid for them.

You said you would put in a built bottom end if you can afford it- so but some 317's instead of some AFR, ETP's and buy the built bottom end. reason- easier to swap heads than build the bottom end.

joblo1978

iTrader: (14)

the key to getting a good FI setup is getting a good NA setup.

'Trust'

iTrader: (24)

I'm not sure if that is necessarily true. Max effort NA setups have a lot more overlap and bigger cams, higher CR etc. than boosted apps. However I agree that you can't just throw boost at a motor and expect stellar numbers without some support. Anybody can make power, very few setups extract every possible gain because they are not ideally matched.

IT_SS

iTrader: (5)

sounds like the heads offered by patriot

I was told by Thunder that the LS2 Cheater has too much overlap for FI. I believe they designed a cam with similar duration, but less lift for FI, but hell, if u get good results with the LS2 Cheater, I'm all for it, I still want one...