5.7 piston rings

[Mudnyri1]

I have a 1995 Mercruiser 5.7L. Is there a standard Chevy 350 ring that works besides the Mercruiser ring package? Mercruiser rings are like $50 per piston Chevy 350 rings are $60 for a whole set of eight this is why I'm asking. Standard Chevy oil ring Gap is .200 or .165 thousands of an inch the Mercruiser piston Oil ring depth is around .800 thousand.

 

[Scott Danforth]

I have a 1995 Mercruiser 5.7L. Is there a standard Chevy 350 ring that works besides the Mercruiser ring package? Mercruiser rings are like $50 per piston Chevy 350 rings are $60 for a whole set of eight this is why I'm asking. Standard Chevy oil ring Gap is .200 or .165 thousands of an inch the Mercruiser piston Oil ring depth is around .800 thousand.

welcome aboard.

remember, Mercruiser just buys a GM longblock.

talk to your machine shop. make sure to hone to +.001 of a standard truck hone. ring gap is dependent on your piston type. cast, hyper, forged, etc.

 

[alldodge]

What Scott said
Merc did not make the motor GM did

 

[Scott Danforth]

I will add, if you are rebuilding a motor, now is the time to make it better than what GM sold Mercruiser

 

[Mudnyri1]

welcome aboard.

remember, Mercruiser just buys a GM longblock.

talk to your machine shop. make sure to hone to +.001 of a standard truck hone. ring gap is dependent on your piston type. cast, hyper, forged, etc.

I have been researching this for the past 2 months Mercruiser Pistons are different than Chevy 350 s the ring Groove depth on the oil ring is not the same as every other Chevy 350 this is my dilemma. Not one piece of information on the internet I have found tells me what that ring Groove depth is for sure. Sierra replacement Rings State they will fit .900 inch to .220 inch Groove depth. Original oil ring measures. .170 and piston Grove is .179

welcome aboard.

remember, Mercruiser just buys a GM longblock.

talk to your machine shop. make sure to hone to +.001 of a standard truck hone. ring gap is dependent on your piston type. cast, hyper, forged, etc.

I'm using the stock Mercruiser Pistons that came with the block. These Pistons are original and have a different Oil ring Groove depth than any Chevy piston I can come across in any enguine spec. Two different ring manufacturers said the Pistons were different for Mercruiser and for me to just use the shallow .165 Oil ring in my piston. Has anybody done that?

 

[Scott Danforth]

I have been researching this for the past 2 months Mercruiser Pistons are different than Chevy 350 s the ring Groove depth on the oil ring is not the same as every other Chevy 350 this is my dilemma. Not one piece of information on the internet I have found tells me what that ring Groove depth is for sure. Sierra replacement Rings State they will fit .900 inch to .220 inch Groove depth. Original oil ring measures. .170 and piston Grove is .179

I'm using the stock Mercruiser Pistons that came with the block. These Pistons are original and have a different Oil ring Groove depth than any Chevy piston I can come across in any enguine spec. Two different ring manufacturers said the Pistons were different for Mercruiser and for me to just use the shallow .165 Oil ring in my piston. Has anybody done that?

If you are re-ringing, you need new pistons and a bore\hone.

Mercruiser bought the same pistons used in trucks, and every other marine motor

Your stock pistons are GM flat tops with 4 reliefs

 

[Mudnyri1]

If you are re-ringing, you need new pistons and a bore\hone.

Mercruiser bought the same pistons used in trucks, and every other marine motor

Your stock pistons are GM flat tops with 4 reliefs

Can you help me understand why Mercruiser oil rings measure .175 deep and stock GM oil rings either measure .190 or .150 not including metric. I'm reusing pistons and crank because the engine had less than 300 hrs on it when the owner did not winterize it and the block cracked. I bought both standard and shallow Groove oil rings and neither of them match what came out of the motor. I'm just trying to figure this out because I found nowhere mentioning that the oil rings are different and they are. That is unless I have a unicorn engine. Thank you for all the feedback I'm just trying to figure this out.

 

[Scott Danforth]

You cant take pistons from one block and put into another block and get good results

 

[Mudnyri1]

You cant take pistons from one block and put into another block and get good results

Thanks for the info.

 

[alldodge]

1995 was a change over year for Merc with pistons. Also a motor might be older then the boat it was installed in because it may have been bought the year before.

https://www.mercruiserparts.com/bam/subassembly/31780/1014/280

 

[nola mike]

You cant take pistons from one block and put into another block and get good results

Why not, if from the same vintage block, and the new bores were honed with new rings? Uneven wear at the Piston pin / rod?
And then the obvious question of why is the op changing pistons instead of using what came with his new block?

 

[Scott Danforth]

Why not, if from the same vintage block, and the new bores were honed with new rings? Uneven wear at the Piston pin / rod?
And then the obvious question of why is the op changing pistons instead of using what came with his new block?

if the pistons are pristine and the block is a new virgin block, maybe. however a 27 year old set of pistons will most likely have collapsed skirts and other issues. a used block will have oval shaped bores with a taper (bore gauge will tell the story). since you have to bore and hone to fix the taper, you already cant use the stock bore pistons

and since a complete cast rotating assembly is about $650 new, its not even worth trying to save. add a few $ and you are in SCAT stroker territory.