piston pin small end rod clearance cl77 305

dave305 · Post by **dave305** » Wed May 23, 2012 6:12 pm

Dose anyone know how much piston pin rod clearance clearance it takes before the engine starts to get noisy on a cl77 305? I have 1 and a half thou. clearance now and am wondering if i should ream to the 15.1 pins because i have it apart or would it be quite at that clearance.

Thank You in advance for sharing the info.

dave305

Goodysnap · Post by **Goodysnap** » Wed May 23, 2012 7:40 pm

Spec is .0006-.0019. Limit .0031. I personally wouldn't go up with only .0015 play.

48lesco · Post by **48lesco** » Wed May 23, 2012 9:36 pm

Goody - Where did you find that spec? I only have the shop manual and it doesn't give a clearance, just max and min for the pin and the hole. We just put an engine together with about .0015" clearance and you could hear the pistons at certain rpm's and power settings. Turned out the cylinder clearance was a little big at .0015 too so probably the combination of the two was a little too sloppy.

Now, to answer to the original question... I'm not really sure. I guess if you have less than a thousandth piston-cylinder clearance, maybe 1.5 on the pins will be quiet. Let us know!!!
-48

Goodysnap · Post by **Goodysnap** » Thu May 24, 2012 12:32 pm

That spec is from Bill Silver's engine manual. I am not an experienced engine builder. Since 15 is within spec I would have to say that it would not cause any issues. I'm curious what clearance is on new parts.

48lesco · Post by **48lesco** » Thu May 24, 2012 2:20 pm

Thanks Goody - Didn't see that in a quick glance thru the Silver book, but I don't think I would put it back together with more than a thousandth. Most car engine specs I've seen are 5-8 tenths depending on the pin size. .0031 is way too much, not sure where Mr. Silver got that number.

dave305 · Post by **dave305** » Fri May 25, 2012 8:37 am

I agree .003 would be way to much clearance and 1.5 is on the edge maybe we could get loud mouse in on this he has reamed a few.

Tim Miller · Post by **Tim Miller** » Fri May 25, 2012 9:33 am

The pin clearance should be .0006" ideally. But I would be ok running .0005 to .0008 with a very smooth round finish "no scoring". .0015 is not good. Your pin should measure .5895 @ 72 F degrees.

Good luck! Tim