[loafing1]

Have a SBC being rebuilt. Had a lot of blowby since I got it and burned oil and fouled plugs. Finally had it looked at and am told the oil control rings were shot, the middle rings were nearly as bad and the top rings were not too bad. Cylinder walls were affected/worn too. Engine actually had decent compression: 150 - 155 per cylinder (dry). The head's pressure tested A-OK.

Is it possible for just the top rings to hold that good a compression?

If fuel wash was the culprit (which seems to be the concensus), would all rings fall prey? I have a gentleman from Edelbrock tech adamantly telling me that fuel wash would wear out the compression rings, not the oil control rings. I have the shop telling me the oil control rings were the worst worn and that fuel wash will eventually wear out all rings.

Any logic as to why it took out the oil control rings so bad first?

Just looking for some other points of view.

 

[The Flyin Wop]

Did you mhave the heads done? If not,maybe you ought to check the valve seals and guides. If when doing the emgine did they bore or hone the block to break the glaze?
Paisano

 

[loafing1]

Yes, valve job was done after pressure testing the heads. They were in very good shape though and the concensus was still that neither the heads nor valves were leaking oil to the cylinders.

Cylinders were bored to .040 (had been at .030), so any glaze would be gone now.

 

[painted jester]

Whoever? may have installed high pressure oil rings with too coarse a hone! different rings some cast, cast molly, steel molly, chrome, racing rings, etc) are honed with different grit stones and some cylinders are even polished, cast ring cylinders are honed finer and steal molly a little coarser etc,etc! high pressure oil rings will wear fast on rough honed cylinders! Thats only one of the causes among meany! And remember Im old so ring technology may have surpassed what I knew and still practice but myself I still hone cylinders different for different ring material and pressures. And cylinders need to be honed for ring break in after boring And a ball hone for deglazing wont do it!!

A lot of older engines had oil holes in the connecting rods that sprayed oil on the cylinders for piston wrist pin and ring lubrication and the oil ring spread and wiped the cylinders and on some connecting rods those oil holes are not machined in!

Ring gaps will cause many problems like you have and ring gaps must be precise! Most rings out of the package have gaps too wide especial when bought cheep for savings!!! I get file gap rings and pay bigger money for better precession and quality But its money well spent for something so impotent! Gas wash usually wears out the top ring, The second and oil control ring get more oil lubrication then the top compression ring So my guess is your second and oil control rings weren't getting good lubrication!


Just a guess ? Jester

 

[painted jester]

Whoever? may have installed high pressure oil rings with too coarse a hone! different rings some cast, cast molly, steel molly, chrome, racing rings, etc) are honed with different grit stones and some cylinders are even polished, cast ring cylinders are honed finer and steal molly a little coarser etc,etc! high pressure oil rings will wear fast on rough honed cylinders! Thats only one of the causes among meany! And remember Im old so ring technology may have surpassed what I knew and still practice but myself I still hone cylinders different for different ring material and pressures. And cylinders need to be honed for ring break in after boring And a ball hone for deglazing wont do it!!

A lot of older engines had oil holes in the connecting rods that sprayed oil on the cylinders for piston wrist pin and ring lubrication and the oil ring spread and wiped the cylinders and on some connecting rods those oil holes are not machined in!

Ring gaps will cause many problems like you have and ring gaps must be precise! Most rings out of the package have gaps too wide especial when bought cheep for savings!!! I get file gap rings and pay bigger money for better precession and quality But its money well spent for something so impotent! Gas wash usually wears out the top ring, The second and oil control ring get more oil lubrication then the top compression ring So my guess is your second and oil control rings weren't getting good lubrication!


Just a guess ? Jester

http://wwwhttp://www.hotrodders.com...forum/attachment.php?attachmentid=66385&stc=1


I see you haven't been back on! But someone else may be interested that doesn't know so I added these pics!

These are pictures of the oil passage in the rod cap ,and the hole in the old inserts, and new inserts with no hole That need to have the hole added for proper lubrication! You can do this with a fine machinists file and be careful not to hit the insert surface or scuff it with the file and clean it before installing!

 

[1971BB427]

If your engine had a severe fuel wash issue, I'd also suspect the oil was diluted and viscosity was lower than normal. This might have caused the excess wear on the oil rings if the oil was too thin.

 

[loafing1]

Thanks PJ and 1971. Since the hone was wore down, it's hard to tell if the rings weren't right for the hone. I do need to ask the machinist if the oil was diluted w/fuel.

I'm still not clear on if it was fuel wash... I understand that it could have diluted the oil and led to worn oil and middle rings, but I would expect the top rings to have been worn too. But maybe it was a mis-matched ring issue more-so than fuel wash, and the middle and oil rings weren't right for the hone.

 

[painted jester]

Your welcome! Chris:thumbup:

 

[1971BB427]

As long as it doesn't happen again, you may never know for sure what caused it. Good luck on the next one!