Valve and piston contact/machined piston crowns

[gitters27]

My c16se build im so worried about valves hitting piston with a 285 cam,i think my head has been skimmed a lot but dont know how to tell?any one ever machined top of pistons?

[therealnovaboy]

My c16se build im so worried about valves hitting piston with a 285 cam,i think my head has been skimmed a lot but dont know how to tell?any one ever machined top of pistons?

What is the valve lift at TDC? Are they standard valves?

Easiest way to tell is a dry build and crank over with some blue tac on the piston.

[gitters27]

I'm not sure but with a cam that has over 12mm of lift it will be close,if I do the blue tach test or if it does touch on a dry build test I should be ok taking some off piston crowns,I have a good frien with a laith

[therealnovaboy]

Is it 12 mm lift at TDC?

[gitters27]

i will have to check once I start putting together I was just presuming that if the cam is 12mm lift it would be at tdc?

[Andy]

Is your head on?
If not take a pic of the face.ya can take loads off em on a skim.

[gitters27]

No head is off its at machine shop at mo but will get some pics when back,will it say on cam details what tdc lift is?

[gitters27]

It's piper 285

[therealnovaboy]

i will have to check once I start putting together I was just presuming that if the cam is 12mm lift it would be at tdc?

its more ore likely to be full lift at around 115 deg ATDC. I would doubt the standard pistons need pocketed.

[mowgli]

Your best bet is to try and find some really weak springs to fit instead of the std gm valve springs, then try a dry build with one piston (without rings would be better) using the old head gasket nipped up. A really good waycto measure the ckearances is to use some solder twisted to look like a spring & sat on the piston top. (This is how lister industrial engines check clearances) then turn it over twice to make sure.

[garyc]

How thick is the head. Std is 96mm.

[gitters27]

just measured the head its just over 95mm so should be ok?

[_Tomiboy]

With c16se head is not possible to hit piston and valve, if the belt not brake. My pistons are running over the top of the block 1mm, my valve lift is 12,66mm and i can advance or retard at least 1,5 teeths without problem.

[BRoadGhost]

While we're on the subject; if you had all singing all dancing aftermarket high CR pocketed pistons, would a valve even touch on max lift at TDC?