Shaving heads?

[Young gun]

Has any one, or dose any one know how much can be machined off the heads of a stranded buick ( cam, piston,crank) And still have the valves open?
and from that would i need special head gasket and studs?
Just pondering.

 

[westerlybreeze]

Vague answer.
Valve clearance shouldn't be a problem, even with a big cam because the valve angle is shallow and the valves are tucked up in the combustion chamber.
Increasing the compression ratio (C/R) adds torque.
But too much of an increase in dynamic compression, you'll have to start reducing ignition advance to avoid detonation, which hurts torque. Solution A: run higher octane fuel, as this counters detonation to a degree. Option B: a larger duration cam has less dynamic compression, as the inlet valve closes later.
I'd be thinking 220 @ .050" 9.5-10:1 C/R, 230 @ .050" around 10.5:1 C/R, 240 @ .050" around 11:1 C/R and that's getting close to needing forged pistons for strong ring lands.
More C/R puts extra load on the piston ring lands and bearings though, increasing wear. Less kms between rebuilds, as the engine wears and becomes tired.
Probably around 11:1 C/R you'd want head studs. The standard head bolts are "torque to yield" so they stretch and can only be used once.

So more C/R the bigger the cam :-D



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[Jack_vs_BT1]

you can take plenty off buick heads, would it be worth it? probably not, 40 thou off = about 0.1 onto the CR there are better ways to increase CR, go for flat tops

 

[westerlybreeze]

you can take plenty off buick heads, would it be worth it? probably not, 40 thou off = about 0.1 onto the CR there are better ways to increase CR, go for flat tops

I'm fairly sure .040" shave will be more than just .1 C/R.
I agree, flat top pistons would be the best way to increase compression.
My Ecotec has ACL Race series flat tops (10:1) and around .040" off the heads with standard gaskets for around 10.5:1, I run a 235 degree cam and BP98

 

[vr304]

Will also have to shave inlet manifold down to suit if heads are shaved

 

[westerlybreeze]

Will also have to shave inlet manifold down to suit if heads are shaved

Only if you take huge amounts off!!

More than around .040" shave and you'd have to start slotting the bolt holes and match the inlet ports.
I heard someone in the states ran .100" shaved heads successfully


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[AirStrike]

Shaving heads makes baby Jesus cry. Do it right and rebuild the short.

 

[Jack_vs_BT1]

Think about it 40 thou off equals 13.2 square centimeter decrease in combustion chamber volume over 6 Cylinders flat tops delete the whole dish in the standard piston I'm not too sure on the volume of standard pistons but I'm sure that it would be a lot more that 13cc over 6 pistons
My Buick is running Clive 48A cam 212/212 and .470 lift with ACL flat tops and 40 thou of the heads and block 11:1 comp with MLS head gaskets, heavily ported heads, stainless valves and double valve springs 165rwkw on a base tune

 

[BlackoutSteve]

Milling Calculator

Assuming 9.4:1 existing comp and a 97mm/3.386" stroke
=.035" to gain one point to 10.4:1

This is a basic guide as to what amount of milling is required, an not what the heads are capable of having removed.
Considerations are piston-to-valve clearances, shorter pushrods, manifold fit..

For every .010" you remove from the head (and/or block's deck), .007" needs to come off the (port) side, and .019" off the base where it meets the China-wall.
So .035" = .025" & .067" off the manifold, and more again if you're also decking.

This is an easy way to get a point of comp, but if you have money invested in these heads or short, do what you need with the right pistons.