I've been trying to file the ring ends with poor success. I am off to buy the proper tool for this tomorrow so the gaps stay square, but I've got a question about the one ring I've "completed." The KB pistons I'm using recommended a .026 gap on the top ring. Due to my own stupidity, I have .026 on the edge of the ring that meets the piston wall, but it opens up to about .035 on the inner edge of the ring. Is the ring now junk, or is it OK to use it? If it's junk, has anyone ever purchased just one ring? Or am I now looking at another set (at least there will be lots to practice with). Thanks.
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Re: Piston Ring End Gap
you can buy a set for just one piston and you will get all 3 rings. the big discount places will not do this because they do not stock this way. try a autoparts. you will also find that the price will be more that 1/8 of the complete set price. buy a hand cranked rotary ring filer to do this correctly -
Re: Piston Ring End Gap
Mark-----
GM sells rings by the "each cylinder". But, whether they have what you need depends on the engine and the overbore. You didn't mention which you have, so I can't advise as to GM availabilty. GM rings are expensive, but if you can't find a a single cylinder set anywhere else, they will be cheaper than buying a whole engine set.
As Clem mentioned, you must get a rotary ring filer tool. This is especially important for the top rings which are molybdenum filled.
The top ring end gap recommendation for KB pistons is critical; make sure that you get it right.In Appreciation of John HinckleyComment
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Re: Piston Ring End Gap
Thanks. The engine is a 327, bored .040. Pistons are KB156. I was going to use the gap specs from KB for the top, and the specs from the shop manual for the other two. I've got a rebuild book that has slightly different suggestions - but all the ranges overlap by at least 4 thousandths.Comment
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Re: Piston Ring End Gap
the reason for the larger than std gap for the top ring is because the KB piston material holds more heat and you have to allow for more ring expansion. do not go too close on the second ring gap,because it is not a compression ring it is a oil scraper. we have found out that using the widest gap reccommended is better because it prevents pressure from being trapped between the top and second ring causing the top ring to flutter and lose seal.Comment
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Re: Piston Ring End Gap
Mark----
Unfortunately, GM does not market piston rings for small block engines in .040" overbore size. So, for a single cylinder set, you will need to find an aftermarket source that will sell piston rings by cylinder set. Most, if not all, of the major engine components suppliers do not sell this way. An automotive machine shop might be your best bet. Chances are that they have some "partial sets" around. The problem is that +.040" (and, +.020", for that matter) are kind of an "oddball" overbore. They shouldn't be, but in the "world of automotive engine rebuilding", the "by-words" are +.030", and +.060". That's what automotive machine shops like to do and is what they do whenever they make the decision or can talk the customer into it.
NEVER, EVER over-bore an engine any more than is ABSOLUTELY NECESSARY. I would NEVER go to +.030", if +.020" is all that's necessary. Likewise, I would NEVER go to +0.060" if +0.040" was all that was necessary.In Appreciation of John HinckleyComment
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Re: Piston Ring End Gap Grinders
Thanks, Joe. Worse comes to worse, I can by another whole set, then I'll have lots to practice with.
These end gap grinders (hand crank) are priced all over the place. About $40 from summitt; $90 from NAPA. Anyone know if there is a difference that justifies the higher price?
MarkComment
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Re: Piston Ring End Gap Grinders
summitt has excellent quality tools . I like mikie waltrup but i'd get it from summitt. mikeComment
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after filing the ring gap
make sure you use a fine hone on all the sharp edges just enought to break the sharp edgeComment
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Re: Piston Ring End Gap
Using the KB chart, I get .026 as the gap for the top ring. Should I try to hit it dead on and if I go .001 or .002 wider, not wory? or is .001 or .002 in either direction OK?
The shop manual only gives two gap ranges. I assume the one for "compression" is for the top two rings, and I should use the widest number in this range for the middle ring?
Thanks.Comment
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Re: Piston Ring End Gap
on the top ring never go below the recommended gap because the ring ends could butt and cause a big problem. i would use the widest number in the specified range and you will never get into trouble. use a fine honing stone to just break the sharp edges on the ends after you fit the ringsComment
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