Snow Dog

iTrader: (3)

Did a good bit of searching but couldn't find anyone that actually gave a value for what the piston to valve clearance should be at a minimum with these engines. I doubt I'm going to have an issue but I'll be checking anyway. Anyone know? I'd like to put it away in my head for future reference.

My setup is Mahle +5cc forged pistons, Ai 200cc heads with 57cc chambers, cam duration 235/244 @ 0.050, .616/.617 valve lift, 0.014 deck height, and 0.026 thick gaskets.

Thanks

joelster

Putting your engine specs up there doesn't really mean you can accurately guess your piston to valve clearance. You have to measure it with the engine mock assembled. There are so many tiny variables that affect it. The machining on the block and heads also plays a part. A safe number to hit is .080"-.100" on the exhaust side and .050" on the intake side. Guys that build race engines for a living will have no problem going tighter than that. The exhaust side is more critical. The piston is on it's way up fast and it is chasing the exhaust valve as it's closing.

Snow Dog

iTrader: (3)

Thanks. That's the information I was looking for. Everything I've read said I should be fine but I couldn't find an actual number.

I'll be checking mine just in case.

BALLSS

mock up motor and use a dial indicator to measure how far piston is in/out of the hole.

As noted block & head decking play a big factor in this...there are options in head gasket thickness available to go +/-

joelster

Valve jobs can have an effect as well. Swapping cylinder heads can change it too. Not every head will have the valves in the exact same place. If you get a performance valve job, you'll be removing tiny bit of metal from the valve and also from the seat. The valve can technically ride higher up into the chamber moving it away from the piston. The reason that they typically go for a higher number on the exhaust side, is to account for any "slop" (I don't really mean to use that term, but it fits). Think of when you take apart a tired LT1, specifically the timing chain. Notice how loose that chain can be. The crankshaft is turning a degree or 2 before the camshaft moves at all. Get some simple checking springs from Summit (usually $9.99) and a dial indicator.

Snow Dog

iTrader: (3)

Thanks guys. I'm set up to check it once I get the engine back. I just couldn't find an actual number that people recommend as a limit with the searching that I had done. That just got me thinking so I thought I'd ask. Thanks