Piston protrusion tolerance

[maldotcom2]

I'm building a motor and the pistons are protruding .015". Does anyone know if this is going to cause a piston to smack the head or will the HG thickness be enough to eliminate this risk? I'm not sure how much the HG will compress when it's torqued down.

[Brett_jjj]

If the block was machined,the machinist should be able to tell you if you can run standard type pistons,or if you will need the recessed top type pistons so they wont hit valves etc.So ask them about it where you had the machining done.If its a standard deck height,and the pistons are the right type for the engine it should all be ok.Maybe also ask them about it where you bought the pistons from.

[maldotcom2]

Pistons are higher compression, but as I understand it, they just make the dish shallower, not increase the height of the piston. The deck was skimmed .004" so bugger all. Thanks.

[MrWooFarkinHoo]

Also depends on heads if they have been decked or not, valve springs etc.

[delcowizzid]

typical ecotec they allways stick proud of the block

[maldotcom2]

Well i'm glad it's not too far out of the ordinary. Heads will be skimmed minimum, Valve springs are Crow 105lb.

[RX25SE]

From memory about 36-40 thou min for piston to head. I reckon a head gasket would be around 60 thou.

You can check compressed gasket thickness by (you have to sacrifice a new gasket) making a hole in it and placing a small lead ball (shotgun pellets work great) and pulling down the head. Then just pull it apart and measure the ball.

[immortality]

i though most gaskets come in around the 040" cometic come in .040" and .060" some perfomance gaskets are thinner, around the .028"

places that sell headgaskets should know what the thickness is

[maldotcom2]

Yep just checked mine, they're .060". Even if they compress half that i'm still ok. Thanks guys.