Finished my engine today to about the 3/4 mark complete. Most of the day was spent fixing a lifter bore, but eh. Anyway, since I had pushrods (8.15in/9.2ex, 1.7 ratio roller rockers) and everything I was going to check P/V clearance. We didn't have any clay or anything compressable like that. My grandpa was there with me. He built helicopter motors for a living and that and just him being there made me confident at the time on how we should do it: he suggested that I coat the entirety of the valves with lipstick. We would then set everything down and set lash, etc, and crank it over, then check if any red was on the pistons, since it would be very easy to tell. Well, they weren't. This made me feel okay and such, but tonight sitting here later thinking about it makes me worry again a bit. I want to trust my grandpa but you never know, maybe his memory is a bit fuzzy or something. I know this is the second time I've asked this in two weeks and I didn't do it 'right' this time but I guess best I could at the moment. What do you guys think of my clearance issues?

The block is zero decked but the piston just barely comes out the top of the bore, and with a gasket it does not pass the height of the gasket. I'm running SRP p/n 139515 (or whatever it's new p/n is), on a cast rod. It has a 23cc dome, so pretty small I'd say, to get me to around 10.5CR with Brodix Race Rite 115cc heads. The cam is a 402A3LUN (solid, 276/284 dur, .584/.600lift [not sure on intake but am sure of exhaust], 112LSA). Cam is installed 'dot to dot.'

Anyway, I know the 'true' answer...just curious though while I sit here, not working on the engine, what you guys would think...

Thanks!

it could have only .003 clearance and not transfer the lipstick. that only tells you you don't have actual contact, not how much clearance there is. can you get the valvesprings off a cylinder? if you can do that you can check by bringing the engine to about 20* BTDC on the overlap stroke with the valves lashed, push them down till they hit the piston, record the number. move to 15* BTDC, check again. keep doing this every 5* till you get to 20ATDC to be safe. the closest usually isn't right at TDC, it'll be a little before or after depending on the cam and where it's degreed in. Otherwise, it's clay or Play-Doh method.

Tom

Play-Doh! smile.gif

Taylor, listen to Tom (And Gene--Doh!) Dont let it go, Im building and engine right now because last year I was "pretty tight" on piston/valve clearance, but gambled that I would be all right....well, I wasnt. Dont take a chance with all your hard work. John

modelers clay $ 2.49
piston and valve hitting $$$$$$$$$$$$$$$$$$$$$
pick your poison

Thanks guys, I do know it's the right thing to do.

I think the problem I seem so stubborn (and I really am not trying to be on purpose), is because I don't understand why even need clearance if it is not touching. It just seems to me that if I have some clearance it's all it needs because the valves wouldn't hit at any time during the cycle? So what am I missing?

rod stretch,piston expansion,valve bounce edit: or float :D ... .003 wouldnt be enuff.

Ah ok, makes sense now. Surprised I didn't think about valve bounce, and I'm sure valve float would be a factor too. Thanks.