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pistons

bulldurham

Platinum Level Sponsor
I have a set of .030 over pistons w/ 4 grooves. Thinking they may be early, Series I-II. Anyone know for sure??
 

bobbo

Gold Level Sponsor
Have 20 thow over pistons in my SV 1725 with 4 grooves. The 20 thow ring set came with 2 sets of oil rings. There is a lot of opinions on whether to use both sets of oil rings or just leave the 4th groove empty. I decided to install all the rings. Seems it's a personal decision.
All the best on your rebuild.
Mine goes back in, in two weeks.
 

bulldurham

Platinum Level Sponsor
You are well ahead of me. One one of the pistons the 4th ring was broken , so this engine will have 1,2,3 w/ 4 rings and #4 will have 3.
Couldn't see $65.00 for a new set. All the rotating assemblies are in now. Not in a big hurry to get it done but I have a O/D trans waiting for it.
Hope your project goes well.
 

junkman

Gold Level Sponsor
I think the forth ring, (on the bottom of the skirt ) is generally left empty. Using that ring causes the cylinders to run too dry. As told to me by Rick at Sunbeam Specialties.
 

Gary T

Gold Level Sponsor
I would recommend that the Sunbeam Work Shop Manual be used to insure you have the correct pistons for your engine. Series I is 1494 cc and Series II through IV are 1595 cc and have at least 4 different diameters for the piston. The Manual does not include Series V 1725 cc engines.

On page 38 under Scraper ring is a note that "One slotted type scraper ring is fitted in the third groove. No piston ring is fitted to the fourth (lower) groove which is only provided on 1494 c.c. engines for fitting of an extra piston ring after the engine has covered a very large mileage." There is no explanation given for "very large mileage." but it seems clear that only the 1494 cc engine has 4 ring groove pistons, even though later replacement pistons may have 4 grooves, but normal ring sets only include 3 rings in my experience.
 

Gary T

Gold Level Sponsor
I also had the experience with my engine that had 4 rings installed with very little mileage when I got it, but when I took it apart I could see that the cylinders at the top indicated cross hatch hone marks, but in the ring area, the cylinders were shiny like chrome indicating to me lack of oil lubrication. I have since replaced only 3 rings after I added the cross hatch pattern with a hone.
 

RootesRooter

Donation Time
I know rings don't weigh a lot, but I'm surprised you chose to assemble it out of balance.


You are well ahead of me. One one of the pistons the 4th ring was broken , so this engine will have 1,2,3 w/ 4 rings and #4 will have 3.
Couldn't see $65.00 for a new set. All the rotating assemblies are in now. Not in a big hurry to get it done but I have a O/D trans waiting for it.
Hope your project goes well.
 

bulldurham

Platinum Level Sponsor
Each piston and rods were individually weighed and they were matched to keep weight even;. the average variance appears to be about
.004 between cylinders. But after reading some of the above, esp about dry cylinder walls from the 4th ring, I might go ahead w/ a new set of rings
 
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