Quote:
Originally Posted by silver911rdb
Interesting read. My 1984 911 was built with JE high compression special make pistons. They're high dome, 12.5:1 compression with 22mm rod ends. I had a fuel related issue and ended up melting a hole in one of the pistons, requiring new replacements. When ordering a new set from JE, they suggested the latest improvement would be to order them with the thinner rings. I went with their recommendation and placed the order. The engine did make more power, unfortunately it was short lived. I started to get massive blow-by with about 5 hours on the engine. I did a leak down test and the numbers were bad on all cylinders. Taking the engine apart showed that all the pistons had a large amount of carbon buildup, especially on the oil control rings. Not really having much faith in the JE piston rings, I contacted Total Seal to see what they offered. They told me that they didn't know why JE piston was recommending the narrow piston rings for the air cooled 911 engines. They designed a set of rings that they thought were going to make the pistons work in my application, although it wasn't ideal. It's been 20 hours since I installed them and I'm having a blow-by issue again. Measuring my original JE's pistons with thicker ring widths, the top and middle ring measure .056" (1.4mm) thick, the oil control ring measures .113" (2.87mm). The updated JE piston set spec's out 1mm top, 1.2mm middle, 2.8 oil control ring.
So in my experience, I don't recommend the thinner piston rings. To resolve the issue I'm thinking I should widen the ring grooves and install a new set of piston rings. I like what Henry Schmidt says about the Goetz rings. I've done a quite a few rebuilds over the years and have used their rings. I've never had an issue. I wasn't sure I could use their rings on a track car, but from the sounds of it, I could. Does anyone know if Goetz has an option for my 98mm piston in the above wider widths?
|
I just installed a set of JE pistons reluctantly. Too many unanswered questions for me.
Ring gap differences, RA, differences, conflicting advice from different people.
I ended up using a slightly higher RA of around 10 to 12 hopefully to help rings seat a little better. I also split the difference on ring gap, I don’t understand why JE doesn’t take expansion of nikasil/ aluminum cylinders into consideration when advising ring gap on these motors. If I had to do it again I’d just spend the extra $$$ and go with mahle and goetze.