Engine: Ring gap for 289 V8 w/ hypereutectic pistons

[bsrosell]

hi,
have '57 Golden Hawk, freshly bored .030 over, and new hypereutectic pistons and Grant cast iron rings.
Noted that the piston instructions dictate increasing the ring gap on the top compression ring by 40% over "factory spec", due to tendency for these pistons to absorb more heat in that top ring.

OK, Stude spec is 0.008 - 0.016" for both rings; sound reasonable to simply take the mid-point (0.012") and add 40%, and shoot for filing the #1 rings down to 0.017" gap?

Fresh out of the box they were at about .012"... (2nd compression ring is already around 0.016, or at least the only one I've measured so far. Would have been a lot less grinding to open THEM up a bit ;-)
thanks!
Barry

[bezhawk]

I used .019 top ring, and .017 second ring. Moly rings, but that was .060 over pistons. General rule of thumb is .003 for every inch of bore.

[swvalcon]

Barry It's your top ring you need to worry about. The second one no so much.What brand piston are you using? I would think you would be ok at .016-.017 on the top and if your at .016 on the second I would leave well enough alone. Keep in mind the second ring should be down just a little in the bore when you check it as it will never see the top of the bore or at least you hope it never does.

[JoeHall]

About 35,000 miles and four years ago, I installed .030" over, hyper pistons in a 289. I used K-B pistons, and chrome rings, bought from Fairborn. Looking at the logbook, I set the top rings to .020", and left the bottoms at .017", as they came. For the first 10,000 miles or so, it got over 5000 miles per quart of oil, and is still getting way over 2000 per quart. So I think I'd go with .020" again. Better a wee bit loose than too tight.

[Mike Van Veghten]

I'd think the .016"/.017" is good.

When I was racing my Anglia (small Chevy), I found the closer I could get the gap, the better the engine ran.
That's why I chose to run Gapless (2nd) in my stock bore 259, with a .015" top gap on the stock piston.

Mike

[bsrosell]

Thanks guys,
I have Silv-O-Lite hyperE pistons and CAST IRON Grant rings. I installed the 2nd ring in a piston and using that to uniformly push each ring down to exactly the same depth , an inch maybe??? (and, they are freshly bored .030 so should be uniform diameter). YES, only tuning the top ring; the SilvOLite insert said leave (or make..) the 2nd and Oil ring per engine specs... which I will. Not going to be pushing it hard, but it DOES have a supercharger and have to have a little fun with it sometimes :-), so figured I better open up that top ring as instructed at least that much. Will shoot for at least .017 on those top rings then as planned. Thanks again for confirming. As Bez quotes Lincoln about believing the internet ;-) (love that quote!),.... I found rules for ring gap from .003 per inch of bore to .005 per inch, and every specific number inbetween. Obviously going with SilvOLite's instructions, just wasn't sure in this situation where you call "factory spec" to multiply by the 40%.....
Have a great weekend!

[swvalcon]

The issue you have with Hyper pistons is the fact they retain more heat then a cast piston. This causes the ring to run warmer and expand more. The reason for the extra gap is so the top rings don't butt when hot and break or stick to the side wall. To much end gap you have blow by and to little they could butt so it's kind of a catch 22. You need to just find a happy medium .

[PackardV8]

I have Silv-O-Lite hyperE pistons and CAST IRON Grant rings

I much prefer the moly-filled rings, but have been told they're NLA in regular V8 overbore diameters. Has anyone found a source for the moly?

jack vines

[swvalcon]

Jack have you checked to see if they are available for a chev 194 six. A little more work to get where you need to go but works. Although they are not a high demand rebuild either.