Head skimming

[ChowderV4]

Im finishing off rebuilding my engine for this season and want to get my head skimmed.
Am i right in saying the common amount to skim off an undamaged head is 0.5mm and remove the base gasket.
Or do i need to find out the squish, as the engine is fully apart already.

[viffer]

The squish is affected by skimming the barrels not the head, check the squish during your rebuild and skim off the barrels the required amount.

[J.B]

Hi,
0.5mm off the head is fine, no problem with valve to piston clearance.

Be careful with how much you have taken off the barrels.
I've tried a few amounts and sometimes gone to far and had to put an extra base gasket on to give a safe piston to head clearance.

JB.

[ChowderV4]

Hi,
0.5mm off the head is fine, no problem with valve to piston clearance.

Be careful with how much you have taken off the barrels.
I've tried a few amounts and sometimes gone to far and had to put an extra base gasket on to give a safe piston to head clearance.

JB.

Do you have to skim the barrels too or os it okay just to skim the head, i can get the barrels resurfaced so have a very very small amount taken off to give a fresh surface

[J.B]

No you don’t have to get the barrels skimmed.

It all depends on what you’re looking for and how confident you feel about measuring the clearances.

If you’re looking to up the compression and squeeze every last BHP, look at the barrels as well. Upping the compression doesn’t automatically mean more power, you can go too far! Make sure you’re confident you can accurately measure the piston to head clearance.

I’d dry build the engine first to measure where it is at the moment. You then have a datum to start working from.

JB.

[rmkd177]

I would foreget all about skimming your barrels...by the time you have removed the base gasket the squish will be too tight any way so you need to machine the pistons...and you will find each one varies too. Do you realise the squish is dependant on what max revs you intend to use? and the weight of the piston. You will also find that your valve timing may have to be compromised to get sufficient valve to piston clearance unless you have facility to machine the piston valve pockets. The easiest way is to remove the base gasket and do a dry build and time your cams where you want them...check the valve to piston clearance...and remove the excess clearance off the head...leaving a bit in reserve. What most people dont allow for is the valve timing retarding when the cam chain wears...which brings the exhaust valves closer to the piston...more often than not you will find a 'dropped valve ' is usually the exhaust valve for this simple reason.Hope this helps a bit.

[ChowderV4]

Thanks for all the info, i'll get the engine dry built and see where im at, and go from there.

Much appreciated guys