Engine build snafu, Techi question for motor heads Options

[Joe Ricard]

Got back to my engine after one heck of a busy month.
put all the valve train geometry stuff together and started on an intake valve.
1st go around I was just looking to see where I was in terms of max lift.

as the engine came around valve opened to .410 and the engine stopped.

I have piston to intake valve interferance.

I have more than likely done this to myself as I am building this engine a bit out side of the box and not a well defined recipe.

Pistons are 97mm Arias with a 8cc dome
Rods Wasserboxser
crank is 71mm with type 1 rod journals
cam is web split duration 86a +5 163 (No cam card available).
Heads are 2.0L 914 that had .010 flycut to true the sealing surfaces 59cc combustion. Dual valve springs.
Already running .210 base shim

Deck is .035

Makes for a compression around 10.6 ish


I guess the best way to fix this is bigger shim. Can't find my books as a result of my recent move. what is an acceptable valve to piston clearance so I can get the right size shim ordered.

This is going to be my autocross engine an I intended to ring it's neck A LOT.
at least 7500 RPM

[DNHunt]

Joe

If I remember Jake would like .060" on the intake and .080" on the exhaust. I don't know how hard and fast that is. What the heck is the compression ratio? What is the deck height? Are you sure the cam is timed right? Adding more shim will decrease the quench. I know quench causes turbulence in the charge so air and fuel stay mixed and the burn is more efficient. I had some 2.0l heads that were decked pretty good. Chamber volume was around 51 cc and my pistons were flat tops with valve pockets. I had a deck of around an 0.050 deck with the shims I had. That setup had plenty of valve clearance. The next time I put it together with 51.4 cc heads flat top pistons with no relief same deck and clearance was tight. By the way the first engine had a static compression ratio of about 10: 1. The second was higher still. I know you mentioned the pistons are domed but maybe some discreet valve pockets and a wee bit of shim? Argh, wish I could be more help.

Dave

[Joe Ricard]

.060 to .080 clearance ??
crap that's a mighty big shim.

[DNHunt]

Joe

I'd talk to the authority. I'm just going off memory. You sure the cam and crank are aligned right?

Dave

[Mark Henry]

....valve opened to .410 and the engine stopped.

I have piston to intake valve interferance.

.... Dual valve springs.

Is the retainer hitting the top of the guide? With that much lift you have to tirm the tops of the guides down.
Also look for coil (spring) bind.

[Joe Ricard]

These are re-used heads from my old motor.
Old cam was 86B
No coil bind
not to the retainer as far as I know but I will go check it again.

But looking into the intake port I can see piston and valve CLOSE proximity.

[Joe Ricard]

Joe

I'd talk to the authority. I'm just going off memory. You sure the cam and crank are aligned right?

Dave

Never mind.

Guess I didn't get the cam gear lined up right. and I was being so carefull too.

Well it pays to just sit back and chill before making a bad situation worse.

Should be good now.

Thanks Dave, Guess I owe you a beer when ever I get up that way.