Oldscoolnew

Thats exactly what I was worried about with the larger chamber volume of the 317s loss of power on the lower end especially because the cam I chose has a power range of 1500-6700 rpm. So yea i grabbed some 799's with the steel valves I don't think i'm going to mess with having them milled I dont want clearance issues with my manifolds or push rods. There with the machine shop now getting cleaned up hopefully no issues and I can assemble this beast!

Redbull87

iTrader: (3)

Dont think of it as a loss of power..just not where your power range will be ideal.And having my 243 heads .030 with stock head gasket did not affect my pushrod length or intake manifold sealing. I believe if you mill past .050 is where you run into intake angle/seal issues.Trust me you will want every point of added compression you can squeeze and right now is the time to do.If my heads come back off...thinner gaskets are going on!

Oldscoolnew

right I meant lack of power on the lower end. Cool so no clearance issues. What pistons are you running i see you have the lq4 as well is it the stock dish? I grabbed a set of sealed power flat tops to throw in mine. Just want to make sure I stay safe with pump gas I'll have to dig around and find what my compression will be if I mill them with the flat-tops and 243's.

Oldscoolnew

Ok thinking about milling the head .030 but worried about clearance due to my cam lift. Cam specs are as follows:
Comp 269lr HR12
Valve lift .607 .614
duration 269 277
Duration at .50 219 227
Lobe lift .357 .361
Rpm range 1500-6700
What do you guys think ?

IllusionalTA

iTrader: (9)

Found this while browsing.. Sorry for the old thread bump... So you're saying milling over .050 will kill flow? Interesting.. I'm gonna call BS! You have any factual data showing your statement? Just curious as i've milled my off a junkyard motor 317's .075... Made quite a bit of steam... If youre gonna run a aluminum intake then it's the logical choice.. IMO...

IllusionalTA

iTrader: (9)

Flycut them piston's.. lil added insurance..

Redbull87

iTrader: (3)

Illusion alot of guys wouldnt dare go to the length of milling the way you have lol. I cant argue your facts of going over .050 as its working very well for you.I think the bigger issue is that guys dont want to deal with the intake seal issue.I would imagine you would mill the intake angle down to match the heads and be on your way? Or do you have to run an aluminum intake at that point?

Not sure about the whole killing flow of the heads point since that will depend on alot more variables in the heads being ported or not etc. Care to share your thoughts based on your findings,Im curious.

bww3588

iTrader: (49)

Call bs all you want. The fact remains that milling a 317 down far enough to match a 243 chamber will shroud the valves and hurt flow. You cannot turn a 317 into a 243 by simply milling.

Search on valve shrouding. I'm not doing your dirty work for you.

IllusionalTA

iTrader: (9)

while theory sounds wonderful on paper.. But it's moot on my combo.. The only time you're goin to see a issue with shrouding of the valve due to milling excessively, is .125 and up then you start running into the horizontal portion of the chamber.. Which I'm nowhere close to that @.075. My heads are at my porters I'll get some numbers for you guys..

bww3588

iTrader: (49)

I'm not saying you can't or won't gain by milling. Read the posts again. Apple's to apple's, if you take a stock 317 and mill it to 243 chamber size, the 243 will still out perform it to a degree because the valves will be shrouded more than in the 243 head. It may not be a huge difference, but it will be a difference.

IllusionalTA

iTrader: (9)

It's actually due to the better chamber design, "not" the shrouding of the valves.. this is actual data.. Not theory.. Fwiw p

bww3588

iTrader: (49)

Valve shrouding is also...actual data...not theory.

IllusionalTA

iTrader: (9)

Yes it is actual, but just not in this case.. Haha

IllusionalTA

iTrader: (9)

there's more than one way to skin a cat.. You can mill the intake which is tricky with thd composite stuff, or the face of the intake.. I opted to shave the intake as it's easier since I'm running a alum intake.. The lil dowels that align the plastic guys up, will be your main issue.. With alignment along with the fact the intake ports are closer to the center of the head, in that case I'd probably try to get face of intake machined but in all honesty it's really not worth all that trouble.. Not much power left on table between 11.0 and 11.5 if you know what I mean.. I mainly did it cause of my own thinkin, and budget at the time.. It just goes to show most that there is tons of power in these castings, just need to put together a tight valvetrain, and make it all work...

bww3588

iTrader: (49)

Maybe not in your mind, but yes it is. Anytime you mill a head you increase valve shroud. It's exponential, the more you mill the worse it gets. It just takes a certain amount to see any measurable difference. In your particular case, unless you opened up the chamber around the valve, I'm willing to bet it's costing you some power.

1BAD98LS1

iTrader: (33)

He has an aluminum intake which is why he was able to get away with milling that much and avoid seal/fitment issues...

1BAD98LS1

iTrader: (33)

I doubt that little tiny performance difference is worth the 300 more dollars it takes to have a set of 243's as opposed to 317's...

bww3588

iTrader: (49)

You would be surprised. Look at the ls3 heads and how much they lack putting them on a 4 inch bore. You move up to c 4.030 or 4.065 bore and the valve is not as shrouded.

Is it worth the extra money to purchase a set of 243's over 317's? That's up to the purchaser.

bww3588

iTrader: (49)

Also, having a composite intake does not keep you from having the intake ports line up with a deep mill. No, you can't mill the face of the intake, but you can mill the intake side of the head.

KCS

iTrader: (20)

I'm having a hard time visualizing how milling shrouds the valve.