Valve to piston clearance

[Error404]

Does anyone have a figure on the valve to piston clearance on a stock engine (3B / ABY) with stock cams?

Cheers
Alex

[UrS4boy]

Does anyone have a figure on the valve to piston clearance on a stock engine (3B / ABY) with stock cams? Cheers Alex

Obviously less that zero for the intake valves (it is an interference engine and when the cam belt breaks, at least two intake valves get hit and bent by a piston).

As for the exhaust valves, I'll have a look (don't be TOO hopeful, it's likely not something that the factory felt necessary to put in the engine manuals (no normal need)).

[Error404]

Cheers Dave, yes its definitely interference.
To be fair the factory info is wrong for things like the compression ratio so not sure i'd trust their info anyway!
I really wondered if anyone had ever done the play-dough trick with a mock build-up to ascertain the exact minimum clearance present on the factory engine.



Oh and it shoud be "too hopeful"

Sorry I couldn't resist it Uncle Dave

[mcandmar]

I went through that process with bluetac to measure the clearance as my head has oversize valves in it, i'll see can i dig up some notes from it tonight.

[UrS4boy]

Oh and it shoud be "too hopeful"
Sorry I couldn't resist it Uncle Dave

Fixed.

Jeez, one brain fade (on the open front diff/engine compression) and people start piling on.

[Error404]

I went through that process with bluetac to measure the clearance as my head has oversize valves in it, i'll see can i dig up some notes from it tonight.

That would be awesome if you can Mark

[mcandmar]

Annoyingly i cant find my notes anywhere, it even had all my crank clearances on it

I need to measure it all again as i have changed the block since then so i really need to find them as a point of reference.

All i can remember is my pistons have the valve cutouts .5mm deeper so it had plenty of room for the valves. The bigger concern for me was the raised squish area of the piston as both the head and block had been skimmed but it was fine too. I had measured it with the new head and an original head for comparison. We did discuss it here a long time ago but the thread is probably long gone by now, i'll keep looking for them..

[Error404]

Cheers Mark, I found a couple of threads from about 9 years ago but no concrete figures. There is a guy on Classic Audi who is also using Wossner pistons and I think is planning to check this dimension. Otherwise I will just get my block decked to level it, get it bored and then to a dummy build-up and check it with blu-tac or the like. Then I can get more machining done as required. Just means more trips to the machine shop!

[s2driveruk]

9years ago....now that's an archive

[Error404]

I found a classic quote a while back from Jamo posted many moons ago, can't find it again now