Which Piston Rings

[scottiec]

Hey Gang,

Unfortunately, I lost the “junkyard lottery” on the explorer motor I originally put in the car. So I am rebuilding a 302 and am running into some conflicting info.

The motor is out of a 87-92 Mustang. I am seeing two different size piston rings on the market for it 5/64 and 1.5mm. I am reading that at some point ford switched from standard to metric rings.

Can anyone point me in the direction of what size I need?

Thanks!

[mike223]

The rings are dictated by the piston you're using.

So, if it's a metric piston made for 1.5mm rings - that's what it needs.

Same for for 5/64.

[scottiec]

So do I meassure the ring land or ring to determine? I’m using the factory trw forged pistons

[mike223]

I'm hoping you can identify the specific TRW piston you have and look up what ring belongs on them from there.

[scottiec]

Thanks mike. I’ll look when I get home. Much appreciated.

[mike223]

So on a brief google search looks like TRW was absorbed by Federal Mogul and is now Sealed Power (maybe ???)...

Sealed Power looks like in 2013 they were making two forged pistons for 289/302 - I do not see any Sealed Power 289/302/5.0 forged pistons currently listed on Summit (?).

But the forged pistons they were making in 2013:

L2488F - 1.5 / 1.5 / 4.0 ring pack.

L2482F - 5/64 / 5/64 / 3/16 ring pack.

1.5mm = .059"
5/64 = .078"

Ring lands are usually cut pretty tight - I suspect a land cut for a 1.5mm ring will measure smaller than .078" (so a 5/64 ring wouldn't even fit in there).


Same deal with the oil rings:

4.0mm = .157"
3/16 = .187'

I suspect a land cut for 4.0 will measure smaller than .187" (so a 3/16 wouldn't fit).


Best estimates.

Good luck.



Correction - Summit still lists the L2482F as a 289 piston.

[mike223]

Vertical ring clearance should be .001 - .003" so the lands should measure just slightly larger than the rings.

[scottiec]

Wow this is really helpful mike. So it sounds like metric rings will fit on two different pistons. Need to be careful for sure

[bobl]

Hopefully you still have the old rings. Just measure them or have a shop measure them to be sure.