I am doing a cheap freshen-up on this engine and have a problem with too much ring gap. I have the Sealed Power 466NP30 cast pistons (.030" over) and just wanted to do a quick deglaze hone and install some Sealed Power E-378 K 30 rings but I am coming up with end gaps on the first and second rings at .032". I'd like to see something more like .017" on the top and .021" on the second. The average dimensions are as follows:

Bore- 4.3830"
Piston diameter- 4.3800"

.0030" piston to bore clearance should be good I think.

Is it possible I have a mis-marked set of .030" over rings? Can I use a set of .040" over and file to fit if needed?

Thanks for any ideas, I really don't want to bore it and buy new pistons right now if I can help it.

Randy

 

Where did you get .017 and .021 as desired gaps?

 

.004" per inch of bore diameter for cast pistons seems to be the numbers I am finding referenced everywhere. What do you like to see?

Thanks,

Randy

 

.0045 per inch is the rule, you need at least .020 on the top and .025 on the second ring.

 

Understood, thanks. Do you agree that .032" is undesirable and likely to burn some oil or affect compression or am I worried about a non-issue?

 

Decided to see what kind of end gap I get with Hastings rings in .030" and .040" over to try and get closer to .020" top and .025" 2nd gaps.

 

You are worrying about a non issue. .032 is probably not ideal but I doubt you will ever see a problem because of it. A few years ago we went to a piston ring seminar that one of the major ring manufacturers gave at the engine parts warehouse we were using at the time. Basically they said that they did tests and did not see any appreciative difference in blow by or performance until the ring gaps started approaching .050" If your bore measures 4.383 then it is worn .002 anyway and that automatically will add almost .006 to the ring gap.

 

Thanks Bill, really appreciate your inputs.

Randy