273 piston ring nightmare!

-

M.Darrow

Mike Darrow
Joined
Nov 2, 2018
Messages
14
Reaction score
8
Location
Pasadena
Hi all, newbie Mike here. I am currently rebuilding my first engine and it’s a small block mopar 273. I am reusing the pistons because they are in great shape and I’m on a shoestring budget. Here’s my problem they are marked .060 over so I tried ordering from JEGS and the ring gap is HUGE! Like 1/4”! But these are the only ones I could find.
1. What should the ring gap be for my rings?
2. Where can I buy some?
Thanks for any help!
 
Dealing with .060 in a 273 can be a problem, (cylinder cracking) of course that bore is a done deal on your engine. My service manual says .010 to .047 on the compression rings and .015 to .062 on the oil rings. It also says that rings are available .005, .020 and .040, it doesn't mention .060, but that doesn't mean that they are not available. I know that 273s have been bored that far, so there should be rings out there, but I also know that after one is bored that far it should be ultrasonic checked. I asked about doing this some time ago. This is the thread. 273 Boring
 
Last edited:
Dealing with .060 in a 273 can be a problem, (cylinder cracking) of course that bore is a done deal on your engine. My service manual says .010 to .047 on the compression rings and .015 to .062 on the oil rings. It also says that rings are available .005, .020 and .040, it doesn't mention .060, but that doesn't mean that they are not available. I know that 273s have been bored that far, so there should be rings out there, but I also know that after one is bored that far it should be ultrasonic checked. I asked about dong this some time ago. This is the thread. 273 Boring
 
Yeah I wasn’t to happy to see the bore # either. I just need this motor to last a couple of years of non hot rodding driving before I finish a nice 360. Thanks for the help. Really appreciate it and I’ll read your other post now.
 
hastings rings, 2m633 +.060. or total seal C3360 +.060. you have to go to a real parts store to get them.
 
Your piston at .060 over should measure 3.685. You sure you don't have a 318? It would measure 3.970 at .060 over.
 
Your piston at .060 over should measure 3.685. You sure you don't have a 318? It would measure 3.970 at .060 over.
It’s a 1966 block and I don’t think the 318 came out until 67-68ish also my piston diameter is 3.662
 
A4B1083B-845D-4590-9656-574BDD04DF2E.jpeg


45CD57B7-8537-4FB6-9166-BEA6C237B80F.jpeg
 
I don't know what's going on. Stock 273 bore is 3.625. 3.660 is .035 over. Pistons are marked .060?
A +.060 should be 3.685
Picture#8 where the dial caliper is at the top of the piston is what I was referring to.Measure them at the top of the skirt just below the oil ring groove and see what you get.
 
How are you measuring the ring gap? I had a friend once who was measuring the gap with the ring not installed in the bore. ........just askin.
 
Picture#8 where the dial caliper is at the top of the piston is what I was referring to.Measure them at the top of the skirt just below the oil ring groove and see what you get.
True, he is measuring at the wrong place, but the difference should not be huge. Given typical piston/wall clearances that .060" oversize 273 piston should measure somewhere around 3.680" at the skirt.
 
I've measured lots of pistons. the top has to be smaller , so it doesn't hit cylinder walls at tdc, when it rocks . also, lets gasses down to seal ring to wall. I've never had a piston be same on top as skirt size. also, the head will expand , since it's in the fire zone.
 
late 66 block could be an early 67 318. Just saying. Casting number on the side of the block?
 
I've measured lots of pistons. the top has to be smaller , so it doesn't hit cylinder walls at tdc, when it rocks . also, lets gasses down to seal ring to wall. I've never had a piston be same on top as skirt size. also, the head will expand , since it's in the fire zone.

Exactly.

The top of the piston can be waaay smaller than the skirts.

The bottom of the skirts of the OP’s pistons should be about 3.683

hastings rings, 2m633 +.060.

Yup.

What rings did Jegs send you?
 
Last edited:
Yes, measure the piston correctly and get back to us. Inquiring minds want to know.
 
-
Back
Top