ksk1980

iTrader: (33)

Anyone milled a set of 243's on a stock bottom end running a ms3? Just wondering on ptv clearance issues.

black00ssFL

iTrader: (24)

Won't fit, you'll have to flycut

ksk1980

iTrader: (33)

Ok though thry might possibly fit since. The lq4 has dished pistons i know this was close in the ls1

black00ssFL

iTrader: (24)

Dished pistons do not provide extra clearance. Here's a pic of the intake valve flycut I made on my engine. You can see how the outer edge of the valve would make contact with part of the piston that is not dished.

Burken01

iTrader: (88)

How much did you fly cut on your piston above ^^^^

I have -2cc diamond pistons, does that mean 2cc total per piston? or 2cc for each valve relief, or 1cc each relief?

I was thinking of milling my 243 heads .030 and using a .040 cometic gasket and running a ms3 or custom cam..

what kind of power would I be leaving on the table if I didnt mill the heads and left them at the stock 64cc and ran the cometic .040 gasket which would put me at 10.6:1 compression or mill and get up to 11.5:1 compression..

what would be the power diff?

ksk1980

iTrader: (33)

Yeah see what u mean about valve getting into the edge of where its dished. What cc valve relief would i need going with a set of flat top 30 over pistons if i milled 20 thousands off of a set of 243243's

JPH

iTrader: (2)

WAY to close. You will need to flycut like others have said.

black00ssFL

iTrader: (24)

I cut .100 into the piston. Using the clay method I had .140 clearance on the intake valve. I'm not sure the exact power you'd be leaving on the table, I think many throw around the formula that every point of compression it worth about 3% tq or something like that, don't quote me. I know the MS3 would love the 11.5:1. I'm running 10.8:1 after milling .030 on my 799's, stock 6.2L gasket, and using a similar cam to the ms3 (comp XE-R lobed 236, 242) and I've been happy so far.

I'm pretty sure the typical 2cc would be fine. I'm no engine builder though (just my own engine, lol). So I'd ask someone with more knowledge than me.

Burken01

iTrader: (88)

if the 64cc 243 heads are milled .030, and assuming .006 milled off equals 1cc

then .030 would be 5cc, so you brought those 64cc heads down to 59cc??

black00ssFL

iTrader: (24)

I didn't actually cc them after milling, but yes, that's the formula I went by and figure my 799 heads are 59cc

Burken01

iTrader: (88)

ok yeah im gonna take mine down to 62cc and run a .040 gasket..

another question is do flat top pistons with valve reliefs change compression like a dished piston would..??

RoadconeTuning

any change in there will change compression... flycutting pistons isnt the easiest thing to do and you can easily go too deep and break thru... I'd suggest paying a shop to do your cam install and flycutting...

Burken01

iTrader: (88)

yeah flycutting seems a little involved.

I was just curious that if my pistons are flat tops with -2cc diamond pistons do I treat it as a dished piston when computing compression?