SPANKY LS1

iTrader: (24)

How much P to V clearance is minimum, what is the least that you should have? Should I have more because my car is an M6? TIA, Shawn

Damian

iTrader: (89)

Shawn, P/V minimum lies in the strength of your spring...

If you've got GREAT spring pressure, IE: no valve float, you could safely run .030 clearance. However, the general rule of thumb for LS1 motor's is ~.080 minimum on the intake, and anything over .090 on the exhaust is good...


josh

SPANKY LS1

iTrader: (24)

I have good springs (Comp 977s). I *thought* that it was .080, but not sure. Trying to calculate how deep the flycuts need to be...

Thanks, Shawn

Damian

iTrader: (89)

.080 is the accepted rule of thumb. I have spoke extensively with Alan @ Futral about this. If you've got 977's, I don't see any reason you'll need more than .080 clearance unless you're running some absolute rediculous lift figures...

SPANKY LS1

iTrader: (24)

Well, you probably consider the lift redicilous, what with your baby cam and all Seriously, the lift is in the upper .590s on the intake side. Think .080 will be enough? I'd like to keep the cuts as shallow as possible.

Shawn

Damian

iTrader: (89)

Well I shoulda asked this first. How much will your heads be milled, and how much advance are you putting in this cam? (IE: ICL?)

SPANKY LS1

iTrader: (24)

I know it'll fit (I.E. Can't publicly say ICL ), I just was curious how much clearance I needed to have to determine how deep my flycuts needed to be. According to my (and Jay at AS and Lou at LG) calculations are as follows:

Assuming my "valve drop" on a flat surface is ~.115 (my heads are not complete yet, but it should be in that range), my gasket is .043, if I flycut .080 I'll have .238 of clearance, Lou at LG says to shoot for ~.225 (that is the magic number to get me .080 of clearance).

So, with an .080 flycut, I'd have .093 of clearance.
So, with an .070 flycut, I'd have .083 of clearance.
So, with an .060 flycut, I'd have .073 of clearance.

Looks like I need to cut them deep

Shawn

Damian

iTrader: (89)

.080 cut is pretty steep on a stock piston. Hope you don't ever plan on spraying..

Whats the point in keeping the ICL secret? That hardly has anything to do with how much power the cam makes. Mainly controls how high/low the powerband is & cylinder pressure...

FWIW mine's on a 114 ICL and does just fine


Josh

AP-Engineering

I too, have always used .080" as a safe minimum on the intake for piston to valve. On the exhaust though I would bump it up to anything in the .110-.120" would be safe.
Also I wouldn't cut the stock pistons any deeper than .080".