11 Bravo

iTrader: (3)

I had read that Diamond grinds the #8 piston to clear the reluctor wheel. None of mine are. What is the best method to do this, and should it be done before the assembley is balanced? Also, do these ring gaps sound right (4.125): #1 @ .020, #2 @ .018? FWIW, the motor will be n/a.

Jason99T/A

iTrader: (21)

If the #8 piston has not been clearanced at all, I would send the piston back to Diamond and have this done. It would be preferred to have this done before balancing.

Your top end gap looks fine, but I would open the 2nd gap to .024".

Jason

Scalpel

iTrader: (4)

Have a machine shop that does race engines do it.

Yes, it should be done before balancing b/c you'll be removing material from the piston.

11 Bravo

iTrader: (3)

Thanks yall. I also heard that when Diamond does grind the #8, they do not take enough out anyway. I think I'll see if one of the sponsors here will hook me up and let me send a piston to them.

SAM98WS6

I ground my own...because I missed the one they had ground in the box. Look real close you might be missing it.
Its no big deal. Just grind a half moon shape for clearance.
My rings are gapped .016 and .018...and thats per spec for a small shot of N2O. I wouldnt go any bigger NA.

11 Bravo

iTrader: (3)

Sam, I looked real, real close at all the pistons and I could see no difference between them. I wish the pistons were marked. I think I'll put the bottom end together and see how much needs to be grinded. If it's not much I guess I could get out the dremel.

Richard@WCCH

iTrader: (3)

Be sure to check the piston to crank clearance from bottom dead center to 30º after BDC. We've seen piston to crank contact with Callies and Eagle crankshafts when using Diamond pistons. The bottom of the piston's pin bosses can hit the counterweight on the crankshaft due to the cam grind on the counter weight. Minimum clearance should be .060" to be safe. Usually the closest point of contact occurs at 10º-30º after BDC. BTW we've seen the results of engines that had piston to crank contact and in one case the piston pin boss was cracked. All stroker engines should be checked for this condition.

Good luck,

Richard

SAM98WS6

I used an air grinder for $10 from Harbor Freight.
Just spin the assembly when you have it all together to make sure there is clearance everywhere. I had to grind the block for rod clearance and that piston for reluctor clearance.

I was told by Callies the little material I removed from the piston was nothing to worry about as far a balance is concerned.

Dont cars suck..

CHRISPY

Can you manually turn the motor over if there is contact there? Or is it very slight? What would the symptoms be? Vibration or something more pronounced?

SAM98WS6

Turning the motor over by hand...it will stop if there is contact. You can see the areas that are hitting/close. Rod Bolts especially.
I put some red grease heaped on the reluctor wheel and kept grinding until there was no residue when it went past.
Wash everything out real good of course.