Oldscoolnew

Hey guys I'm building an n/a lq4 comp camp 1500-6700 rpm range, sealed power flat top pistons, scat rods, stock crank, comp lifters+ push rods, comp rockers, comp double roller timing, stock valves. The plan was to use the stock 317 head I had a valve job on it and assembled it. But now I'm second guessing my choice to use the stock 317 head for my n/a build due to the large head volume. I know alot of people use the z06 heads 243 heads which are basically the same as the 317 just with a smaller head volume at I belive 64cc? Compared to the 317 of 71cc? What do you guys think. Is it worth selling the 317 and getting some 243's? I'm worried about low end power with already having a higher rpm cam.

onefast84

I ran 317s for a long time, and they worked pretty good. I just waited to change them until I could afford some ported heads. It ran in the mid 11s with them. Hoping to break 10s now. I just havent had it to the track yet.

Rise of the Phoenix

iTrader: (27)

Since you're running NA, I'd opt for the 243 heads and have them milled down to acheive the highest compression your fuel will allow. 11:5.1 or 12:1 would be great and give you that low end torque you're looking for.

If this were a turbo build, then the 317's would be your friend and help lower your compression. If all you have is 317's, then they will work, but I'd have someone like Martin at Tick Performance spec you out a custom cam based on those heads and your overall setup. Hell, even if you do get some 243's and run high compression, I'd still have Martin hook you up with a custom stick.

wildcamaro

iTrader: (15)

243 without a doubt since they offer the same port/runner sizes as the 317s with the added benefit of added compression which LS engines love, especially canned motors...if you have the choice 243/799 are the way to go...and they don't have to be the sodium/ hollow valve 243s either unless you plan to spin that Baby higher than the rpm range you listed originally...good luck with the project man

Oldscoolnew

Do you think it's worth it to find some 243 if I already have the 317s cleaned up with a valve job and assembled stock for stock?

wildcamaro

iTrader: (15)

Port size is the same but that added compression will give you approx 10% more horsepower in the upper rpm range...you have to decide if the cost of heads is worth the increase...plus you can sell the 317s to recoup some of the $...it's ur call just giving you my thoughts

Rise of the Phoenix

iTrader: (27)

Looks like everyone agrees that the 243/799 heads are going to be your best option. You can sell the 317's for $130 to $150 and then use that money to buy some 243/799 for roughly $400. I'd say the extra $250 you'll end up spending will be well worth 10%+ HP/TQ.

1BAD98LS1

iTrader: (33)

Why not just mill the 317's that are already cleaned up and already have a valve job and they are already in his possession lol just a thought...

squirlNUTZ

What is compression now? Maybe I missed it

1BAD98LS1

iTrader: (33)

Just a debate on whether he should keep 317's or get 243's, what he does with whichever heads he decides to go with will then determine the compression...

Oldscoolnew

I am running flat tops so I will be at stock lq9 comp which I belive is 10:1. 317s cleaned up with valve job are only worth 150? I paid more for the valve job

wildcamaro

iTrader: (15)

If you mill the 317 to have the same size combustion chambers as 243/799 then you will have issues getting the intake to match up with the ports

Rise of the Phoenix

iTrader: (27)

Didn't realize they were cleaned up with a valve job. It's up to you what to do. You've got a bunch of good advice in this thread, so use it how you want.

squirlNUTZ

Use your 317 heads. Have them milled and use a thin head gasket. You said naturally aspirated but I don't think you mentioned intake manifold?...
In this case I would mill the head, thin gasket and a victor intake and 4150 Accufab throttle body. You can mill the victor intake to match the heads. With the correct valve train it will scream.
The victor will make far more power than a factory style intake. Contact studdern ( not sure on spelling) he just posted some interesting results on another site

wildcamaro

iTrader: (15)

Victor intake isnt exactly a street intake but I'm not sure what his goals/use is for the car, I've checked and those thin head gaskets are only made by cometic which aren't cheap that's for sure..it would be much cheaper to use his current fuel injection setup if that's what he got...there is about a 1000 different way to do things so be should at least have some info to go by...

bww3588

iTrader: (49)

The intake surface of the head can be milled accordingly to match the mill on the deck of the head. Common practice. But milling the 317's roughly .050 to match the chamber size will kill flow and you'll end up at a wash between the 2 heads, or a slightly less potent 317 with the same amount of money in them as a set of 243's

mred

iTrader: (5)

317s
Spend money else where.

jszklany

iTrader: (1)

^^^ put the money behind the motor, heads are fine.

Oldscoolnew

well i went for the 799/243 heads got them off a 08 van lol for $250 for the pair gotta love gm...from corvette to van. works for me ! I dont care about the sodium valves sttel works for me! Now the question can i still use the fel-pro head gasket set i bought for the 317s 2003 6.0?

Redbull87

iTrader: (3)

243 heads are nice bump in compression.I picked up quite a bit of useable power and tq going from stock 317 to .030 milled 243 heads.If you find them at a steal of a price then go for it.If not then work with what you have and save up for a set of aftermarket heads for more gains later on.My only gripe about the 317 heads was how sluggish the motor felt on the bottom end.Now its not an issue and my 243 heads are still stock so my potential to grow is there with doing valves ..port/polish etc.