LS12Fast4U

iTrader: (1)

I have an opportunity to pick up some 317 heads from a junk yard for a good deal and i was wondering if they would be worth it? I know i would need to mill them to drop the compression but other then that would i see a gain using them over my 241's ?

mastercoryd

iTrader: (3)

i wouldnt do that, i'd go for 243's, or work ur 241's, the 317 is used for turbo or s/c applications

LS12Fast4U

iTrader: (1)

Do you think working my 241's is worth it?

conan

iTrader: (5)

X2 on passing up the 317's for a N/A app. I would either shave your 241's to bump compression and have them ported. Or go after a after market casting.

LS12Fast4U

iTrader: (1)

I would love to do an aftermarket head but I can't afford it. I can afford to port and Polish my 241's though.

orangeapeel

iTrader: (18)

Theres your answer.

JonCR96Z

iTrader: (33)

No it's not. It's an idea but not an answer. It could be a way to **** up a set of heads or put money in them for little to no gains.

If you have a reputable head porter or are planning to send them somewhere good, then yeah. On the stock valves even the best porters are only getting ~280 CFM out of an LS1 head, and you'd pay $600 plus for that.

If you can get the 317s for ~$100. And have them shaved .02-.03" and run a .04" gasket then you'd 10.4-10.5 SCR and a had that flows ~265 CFM for $200 or less plus gaskets. No different than guys you run a 243 head with a stock size head gasket, except they have $400+ in those heads. The only downside is it would limit potential cam size if you went that route later, since you've had the heads milled.

LS12Fast4U

iTrader: (1)

That's my other concern. I have the cheater v3 can and I don't want PTV problems.

JonCR96Z

iTrader: (33)

You could always put them on and check how much clearance you've got and cut as much as you can (it's better to take from the head gasket than the heads for a few reasons). I'm sure that you can at least get them to the same compression that you are now and you'd still have a good flowing head for cheap(er).

NHRA4MULA

iTrader: (29)

I have a set of 317 heads that were just done they came with a engine that I bought the heads are fresh and never been ran. I sent them to a head shop to be flowed and cc here are the numbers on a set of 317 ported and milled heads
at intake 0.6000 of lift they flow 273.6 it starts to go down after that.
at exhaust 0.6500 of lift they flow 218.4 it starts to go down after that
the chambers are 69.8 with 10 thousands mill
202 manley valves intake
1.575 manley exhaust valves
with double springs etc....have numbers on springs seat pressure ect...
they are for sale if any one is interested

orangeapeel

iTrader: (18)

Well in short that was what I was saying. I know its not the best option. I ran a shaved 317 on my 99 Z and they were miles better than the 241's I had previous.

Jim_PA

iTrader: (9)

Supposedly the 243's have a better combustion chamber design, so while they may flow the same, the 243's are good for about 20HP over shaved down 317's <from what I've been told>.

JonCR96Z

iTrader: (33)

What type of motor are you talking about a 20hp gain on?

On a near stock LS1 243s are probably only worth 20hp over 241s. The combustion chamber is different and probably better on the 243s but it wouldn't add up to much if the compression was similar. For the price difference 317s are something to consider, but 243s will always be better.

Jim_PA

iTrader: (9)

Sorry, I mis-spoke.. it says 20 ft/lbs torque gain, and I've only ever come across one experiment that talks about milled 317's vs 243's.

The experiment sounds legit, but I guess there's always the chance something was done a little different on the dyno or the tune between the two runs.

The last post gives one guy's experience with each casting:
http://www.yellowbullet.com/forum/sh...d.php?t=116576

JonCR96Z

iTrader: (33)

Yeah, that's on a 427. In this case the difference would probably be negligible. If you're doing a 427 you should probably look for better heads than 243s anyway.