Bad rings, why?

[GreenGSR311]

Ok my GSR has 65000 miles on it. It has been supercharged for about 4000. I was burning about 1 quart every 1000 miles before the supercharger, now it is at 1 quart every 100-150 miles. I did a leakdown and it was(starting with #1 cylinder): 9%, 9%, 17%, 25%. I don't remember the compression #'s exactly, but they were fine and the car still drives completely normal. I know it's the rings and I am rebuilding this winter. Before the supercharger all I had was intake and exhaust and the car was driven normally, barely ever raced and the guy I bought it from is a friend of mine and he didn't mod it at all and he drives like a grandma.

Basically, assuming this was a pre-existing condition, what would cause my rings to start failing before the supercharger? I know the supercharger made it worse alot faster, but it was already happening. Why? Any ideas would be appreciated. Thanks.

<font color="#a62a2a" size="1">[ September 22, 2004 09:52 PM: Message edited by: GreenGSR311 ]</font>

[promotion]

Well, there could be several reasons your leakdown test came out higher in two cylinders and fine in the other two none of wich would have anything to do with bad rings; although I wouldnt rule out bad rings yet. Usually if 2 sets of rings go bad, they all will at the same time unless something else is going on that is cylinder specific. You may want to check the valve oil seals first to see if they are dry and possibly leaking oil into the cylinder; this problem would become worse with the added heat from the compressed intake charge. As for the leaking cylinders, you will want to do the leakdown check again, or at least get compressed air into the cylinders, and find out where the air is leaking. First try removing the air intake tube and running compressed air into one of the cylinders. Listen for air leaking into the intake manifold, or possibly into the exhaust as well. If air is in fact leaking out to one of those outlets, your valves either have a bad seal to the head or are way out of adjustment. My guess is that if the oil seals are leaking, those valves are gummed up and are causing the valve to not seat properly.

If in fact the rings are bad, you can confirm that by dropping a teaspoon of a heavy weight oil, like 10w40 or 15w50, into the cylinder and rechecking the leakdown. If the leakdown test shows a better result, then the rings are bad. Also, you may want to do the compression check when the engine is warm. If the rings are bad, it may not show on the compression check if the engine is cold.

[GreenGSR311]

Thanks for the response. When the leakdown test was done, I was there to watch and you could hear the air leaking from the oil cap when it was removed. So I was under the impression that this meant it was the rings. I will try to go back and do it again with your advice of putting the oil in the cylinder first and see what happens. Also, when the compression test was done the engine was at normal operating temp.
Thanks again.

[promotion]

If the air was coming out of the oil cap it could still be one of two things. If the rings are bad the air would have to leak past the pistons and up the oil passages to the head; however you will have some air leaking this direction anyway since the rings do not hold a completely tight seal. If the valve oil seals are bad and subsequently have caused the valves to not seat properly you would have a little leakage into the valve cover but most of the air would leak into the intake manifold. It is possible that the rings are in fact worn, but I wouldnt rule out the other items yet.

[GreenGSR311]

Cool, again thanks for the info. I think first I will try the putting oil into the cylinder thing first and see what happens, and then work from there. Thanks.