4.380 rings in a 4.372 bore ?

.030 - over 400 block = 4.372 bore, this is a fresh bore on a new build.

I have a set of rings for a .060-over 440 which would be 4.380.

QUESTION: Can I use the 440 rings in my 4.372 400 block ?

The difference in bore circumference is .025 inches, bigger circumference on the 4.380 bore.

My concern is that the 440+060 rings will exert a bit more radial outward pressure on the 4.372 bore, but can't be much more..............
Rings are 5/64, 5/64, 3/16.

Would you or wouldn't you ?

NO!

The factory used to recommend rings be no more than .010" larger than the bore and be filed. The only one I did was a factory .020" over bore 318. I used .030 over rings and filed them to fit. This was in the 1980's and they only place that I could find .020 over rings was order them from the dealer at about $95, I got .030 over rings from NAPA for about $30. To my knowledge, the engine is still running today. We routinely use rings that are .005" over (and file fit) on race engines.
Brian

OK, well now I'm inclined not to use these rings.

However, I have a related question.

I have an old set of Childs and Albert DuraMoly ZeroGap rings. The second ring (ZeroGap) and the oil ring say 4.375 bore,
but the top ring is labeled 4.380. An old C&A ring catalog has the note:

For file fit rings, the part number de-codes as
PREFIX - THICKNESS x BORE SIZE + .005

I think this means that the C&A top ring, labeled 4.380, is .005 oversize. Intended for file fitting into a 4.375 bore.


Now, the rings I was hoping to use are Sealed Power E-424K-060. However the note in the box does not say anything about file fitting these.
So I put one ring in my new 4.372 bore and it does not go in unless I overlap the ends about 1 or 2 thou, negative ring gap !
Meaning that in a true 4.380 bore, they would have about .023 gap.
File fitting NOT needed for these rings labeled 4.320+.060 ?

Thanks for humoring me, but the devil's in the details !

Those rings are what is referred to as "drop in rings", fitting them is not required. However, they should be checked. Also, on file fit rings, the spec that is given is the MINIMUM amount of gap required, with more gap being "acceptable", to a point. A while back I was building a basically stock 390 ford and the drop in rings measured about .048". I called the ring mfg and was told that up to .055" would be ok.

Brian

If they are drop in 4.38 you are fine.