Hole in Piston

[Brian Hood]

I am in the middle of freshing up a 71 5.2. I found a small hole in the skirt. It not all the way through, but its there. Should I replace this piston? If a get just one single piston, because it a little different, will it make other things out of balance?

 

[Abodybomber]

Yes,replace it.I have never seen that before.Sounds like a slap together quickie assembly to sell.

 

[Brian Hood]

I was leaning towards that, but its good to hear it from someone else.
Thanks!

 

[sireland67]

Actually the knurl is completly off the piston.
Look at the rest of them, I but you the rest are the same way??
Check the Knurl.
Time for new pistons possibly an over bore.
It you are doing this on the cheap, I might have an extra piston.
.

 

[Abodybomber]

They knurl pistons radially?All I have seen,do crosshairs or xs.

 

[sireland67]

Knurls are factory radially on every 318 piston I have seen.
They are an indication of cylinder wear.
Most likely wore smooth on the thrust side, as seen in the above posted pic.

If it is a mild build, replace the piston, hone each cylinder and use IRON RINGS not moly.
Iron rings are much more forgiving than not so round cylinders than moly.

 

[Abodybomber]

Sorry,I was thinking rebuilder shop.They usually do an x, doesn't last very long,why I asked.

 

[krazykuda]

The piston is useable. It obviously has been there since originally built in 71. It is not in the fire area and on the skirt. It has lived this long in this environment, it should be able to take more. There is enough surface area of the skirt to distribute the load over.

But if you wanted to be safe, I would recommend replacing it with another one from the same year or buy a matched set. The compression went down after 71 so you would want a 68 - 71 vintage piston set if you don't buy a new set.

 

[moparlover]

if you are replacing pistons you would likely do the whole set since it's a refresh

if you are doing that i would get a set of KB pistons that would get your comp ratio up to 9.5 or so for a nice little boost, and a set of refreshed 360 heads.

if you just replace 1 piston you need to get the assembly balance anyways.

http://www.popularhotrodding.com/enginemasters/articles/mopar/0667em_mopar_318_engine/viewall.html