I have my 350 cast iron block out with pistons removed. It is currently at the shop to get a hone as I had to fill in the face and skim it. Bores are 060 oversize (if it matters)


Question is what kind of rings should I get? Cast, Chrome or Moly?


Engine is basically stock.

 

If it matters, the grit used to hone the bores is 240.

 

240 grit is too coorse for moly rings use chrome ones they will be perfect for that bore finish. Also some pistons use a shallow oil ring ( low tension style) so check see what depth the oil ring groove is on your pistons

 

The pistons that I have are Sealed Power 423NP-060. Do they ring a bell?
Wouldn't using chrome result in high abrasion on the bore? I read chrome are normally used in industrial uses but I might surely be mistaken.

 

Rockauto carry these chrome faced Rings:
MAHLE/CLEVITE 40451 (Material: UCR-Carbon Steel; LCR-Cast Iron; OCR-Stainless Steel; Facing: UCR-Chrome; OCR-Chrome; Axial Height: UCR-5/64 IN; LCR-5/64 IN; OCR-3/16 IN; Ring Type: UCR:RF-13U; LCR:BT-10; OCR: CP-20)


Not sure about the oil ring groove

 

Just confirmed that the oil ring Grove is 0.200 as I measured it.

I just need some explanations on the chrome faced rings as I am reading they are usually used in dirty environments.

 

.060 over on a OEM GM block I don't see many that sonic test to go .060 over. A plate hone is a must at the bore if not once the heads are bolted on there is a lot of cylinder distortion and its pretty hard to get rings to seal.

 

Seal facing material anyone? Chrome seems to be a good choice for cast iron blocks but I don't want to risk scuffing the bore too much!!
I am in a dilemma

 

After some research I came to a conclusion to prefer Molybdenum faced Upper Rings. These will not harm the cylinder walls and will also offer some added oiling on the top ring. I have also instructed the engine shop to hone to 400grit to achieve a smoother, less abrasive surface due to the softer material of moly.
Didn't go for Chrome with coarser hone as I don't want to risk more wall abrasion. Anyway the engine wont be used in dirty environments.


Will go for SEALED POWER E251K which are 5/64 for First and Second Rings and 3/16 for the Oil Ring. They are also 0.200" oil grove deep so they will fit my 423NP Pistons.


Just wanted to let everyone know about my findings perhaps it will help others.

 

Moly rings are a good choice it will be hard to get ring seal if the block was not plate honed at .060

Those are Mack truck rings LOL I have not see 5/64 rings in many years.

Actually a 400 finish is to fine, But it depends on the hone being used as well.

 

5/64 are the ones used by the 423NP.... It's quite a common ring size for pre 1991 SBC

Re 400 grit it is the manufacturer recommended hone for Moly rings on cast iron blocks.

 

I build a lot of Pre 91 engines I don't use pistons with 5/64 rings PERIOD

Never seen a factory block with a 400 finish, I would never use a 400 finish, I have been over my honing procedure with the guys at Total Seal and over the last 40 years I would not change.

 

Whatever the ring composition you go with get a ring that has a file fit finish. My last two engines I built I tried using the pre cut rings and the end gap was only at spec if I had been using Nitrous. Sent both back and bought the file finish. It takes much longer but you will be much, much happier.