Oil Control Ring Gap

Understood........... 0.003" - 0.0035"ish per 1.0" of bore diameter.
Does this apply to the oil control rings as well?
Vendor; Cycle Pro: CS-0113A for a 1973 850 @ +0.060 over

Thanks!

No. Just verify MINIMUM. Usually you'll find it to be significantly larger.

Agree. Also. .003 per inch of bore for the compression rings sounds a bit tight. .004 per inch has been the common spec for many years. OTOH if the manufacturer says .003 is OK, one would ASSUME they know what they are talking about! But you know what they say about assumptions! Frankly I'd use at least .004 anyway, especially since it's an air-cooled engine!

MexicoMike said:

Agree. Also. .003 per inch of bore for the compression rings sounds a bit tight. .004 per inch has been the common spec for many years. OTOH if the manufacturer says .003 is OK, one would ASSUME they know what they are talking about! But you know what they say about assumptions! Frankly I'd use at least .004 anyway, especially since it's an air-cooled engine!

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Do not go tight on 1st and 2nd ring gaps! You have nothing to lose by using generous gaps.

The top ring gap should be more than any quoted minimum. 2nd ring gap should be at least 25% bigger than the top ring gap.

Triton Thrasher said:

Do not go tight on 1st and 2nd ring gaps! You have nothing to lose by using generous gaps.

The top ring gap should be more than any quoted minimum. 2nd ring gap should be at least 25% bigger than the top ring gap.

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Agree, nothing to loose being generous.
My original question was about the oil control ring end gap.
I did not understand concours response; " No. Just verify MINIMUM. Usually you'll find it to be significantly larger.in

Is there a dimension please?

Thanks again!

Typically, for oil rings there is only a minimum gap spec (if that). .015" is fairly common. There is no "gap per inch of bore" like with the top two rings. There is no spec for a max gap and .060" is not uncommon!

Mofosheee said:

Agree, nothing to loose being generous.
My original question was about the oil control ring end gap.
I did not understand concours response; " No. Just verify MINIMUM. Usually you'll find it to be significantly larger.in

Is there a dimension please?

Thanks again!

Click to expand...

Ok.
The compression rings are given a minimum, and a maximum in the repair manual.
It is standard operating procedure, to verify that the oil control rings have at least the MINIMUM specified in the book. However, the maximum specified for the compression rings does not apply to the oil control rings. For example: if the oil control ribgs have .030" gap, that is acceptable. Does that clarify it?

Yes oil ring rails typically have a big gap like you mention , thats OK, the 3 piece ring gets tension on the bore from the ring design , make sure the centre expander is butted , some V8 ring sets like sealed power have plastic blocks on the centre expander to stop the overlap , these can come off later when engine runs and make ugly marks in bore , they can be twisted off , just make sure ends butt correctly, older oil ring designs were 4 piece designs and came with a small depth gauge , for groove depth . Alot of the new forged piston / V8 ring sets for high performance stuff , actually gap the second ring bigger ,I think this is to stop pressure build up between rings and avoid ring flutter , also you may have seen a dished groove on the land between the two rings , I think this is to increase the volume and help with the same .if you you need to increase the rail end gap grind it vertically from the outside in , carefully de-burr on a stone etc . Cheers

concours said:

Ok.
The compression rings are given a minimum, and a maximum in the repair manual.
It is standard operating procedure, to verify that the oil control rings have at least the MINIMUM specified in the book. However, the maximum specified for the compression rings does not apply to the oil control rings. For example: if the oil control ribgs have .030" gap, that is acceptable. Does that clarify it?

Click to expand...

Very much so...............thanks again