How to check running clearances

[JuhaV]

Hi,

 

Putting in new pistons and wanting to optimize the squish band height and also to safety check the valve-to-piston clearance, could you advice me what is the best method to accurately measure these dimensions ?

 

I am thinking of using some soft material on the top of the piston and then rotating the crank by hand. Afterwards I just check how that stuff was squeezed between the engine components.

 

But what is the best material to use for this test ?

Any other methods that have been found practical ?

 

br, JuhaV

[jrt]

Todd H. or Pete R. will probably give you the correct way, but I've read that you can check valve clearance using a layer modelling clay on the piston crown.

J

[pete roper]

Todd H. or Pete R. will probably give you the correct way, but I've read that you can check valve clearance using a layer modelling clay on the piston crown.

J

40372[/snapback]

 

Basically that's it for squish clearance and valve to piston clearance. You just use modeling clay or plasitcene on the squish bands and valve pockets and measure the clearance after 720 degrees of rotation.

 

For valve to valve clearance simply cut a couple of pieces of wood the thickness of the barrels and assemble the heads onto the case so the barrels are *missing* and you can see the combustion chamber from underneath. It doesn't have to be torwued down or anything, just tightened till the head is firm against the wood and won't move, don't over tighten or it will warp, (do this with the rods and pistons out obviously!) install the rocker gear and pushrods and turn the motor over until both valves are on overlap, (TDC exhaust/induction.) and measure the clearance between 'em.

 

Pete