Oil rail support end gap?

[Walter R. Malik]

here is the dimple in place and I never saw one that overlapped. is it overlapped when in the ring groove ???

Not all oil ring support rails have a dimple ...

[cjperformance]

here is the dimple in place and I never saw one that overlapped. is it overlapped when in the ring groove ???

Not all oil ring support rails have a dimple ...

Correct, some supports are overlapped when NOT on the piston but once fitted they do have an end gap, they have NO dimple and are held in position by their spring/tight fit around the oil ring groove.

[cjperformance]

Is there a spec for this?

Went to assemble the short block this morning and noticed that when I put the oil rail support on a set of SBF pistons that the ends slightly overlapped. I assume that I have the wrong rail supports, but was thinking that if I could chuck them up in my ring grinder, I could go ahead and assemble this weekend instead of waiting for parts.

I usually don't check/measure, but I know that supports usually have a fairly large gap between the ends.

Is there a minimum spec on what that gap should be? I'm assuming it would be on par with with an oil rail??

Correct there should be no overlap. Providing they dont protrude past the skirt when fitted yes just file them till you have no overlap. I have not seen a spec for support end gap BUT I have reset the gap to a .020" end gap on dimpled and non dimpled supports and had no problem. Naturally always make sure there is no burr left from filing that will rest on the ring land or for the oil ring to snag on.

[n2xlr8n]

Last set of (oil) rings I rec'd from TS I had to grind the oil rail rings down on-

[piston guy]

DCal is right .015-.020 minimum gap on a rail support. "Normally" they do not overlap but when they do , they can be cut back without any concern.

[piston guy]

Last set of (oil) rings I rec'd from TS I had to grind the oil rail rings down on-

This is fairly common in Nascar and high end drag race engines to reduce oil consumption on "narrow" oil rings. .012 is the minimum gap on the rails.

[swampbuggy]

Hey Piston Guy....in the NASCAR engines 4.185" bore "OR" minus a wee bit, with a 3.250" stroke "OR" plus a wee bit, they get their 358 cu. in. minus a wee bit. So with a 3.250" stroke, a 9.00" deck hgt., a tiny ring package, one can employ a pretty darn long rod and not get the w.p. into the oil ring groove. Are you saying some are still increasing rod length to have to have oil ring support rails employed ??? Mark H.

[DCal]

Hey Piston Guy....in the NASCAR engines 4.185" bore "OR" minus a wee bit, with a 3.250" stroke "OR" plus a wee bit, they get their 358 cu. in. minus a wee bit. So with a 3.250" stroke, a 9.00" deck hgt., a tiny ring package, one can employ a pretty darn long rod and not get the w.p. into the oil ring groove. Are you saying some are still increasing rod length to have to have oil ring support rails employed ??? Mark H.

I think Piston Guy is referring to the oil ring rails in this instance. The rods are typically 6.200 so they are fine w/o pin in the oil ring.

[swampbuggy]

Yes Dcal i understand what was being said, i was just thinking that they could get all the con-rod length they would want w/o getting INTO the oil ring groove, then there by needing oil ring support rails. Follow me ? Mark H.

[Mark O'Neal]

They're supposed to be tight against the back if the ring groove. If they have the dimple that is no longer important.