piston pin small end rod clearance cl77 305

[dave305]

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]

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

[48lesco]

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]

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]

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]

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]

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