Blown 460 Ford Piston Ring End Gap

[lakesmodified]

I'm running approx 10 PSI boost on a .030 over 460 Ford. I contacted J&E Pistons today, and their tech dept recomended .005" per inch of bore diameter for the second ring and .0065"/inch for the top ring. This equates to .028" for the top and .022" for the 2nd ring.... Seemed kind of excessive to me, any thoughts? I know some of you will tell me to use Zero Gap, unfortunately, the set-up I have (5/64" top and 2nd rings) there isn't much I could get right away... Special order..

[blowngas]

Originally posted by lakesmodified:
I'm running approx 10 PSI boost on a .030 over 460 Ford. I contacted J&E Pistons today, and their tech dept recomended .005" per inch of bore diameter for the second ring and .0065"/inch for the top ring. This equates to .028" for the top and .022" for the 2nd ring.... Seemed kind of excessive to me, any thoughts? I know some of you will tell me to use Zero Gap, unfortunately, the set-up I have (5/64" top and 2nd rings) there isn't much I could get right away... Special order..
Thats pretty much the rule of thumb for ring clearance on any blown motor---it also depends on how much of the piston is above the top ring---usually the cylinder temp of a blower motor is more than a carburated motor--thence the larger ring gap---play it safe and do what the manufacture says---be safe and watch out for the other guy

[lakesmodified]

Blowngas, thanks for the input... I had already filed the rings to those clearances, put to tell you the truth, I was about ready to order a new set and start all over again. I've never per-se built a blown engine from scratch, though I have built plenty of normally aspirated engines, and I've always used .004-.005max/inch for both the top and second rings. This was the first time I had heard as much as .0065/inch for the top ring.

[058]

Lakes, I set my .030" over 460 with .022" top ring and .016" second ring. JE pistons 8.4 to 1 C/R Banks twin turbo/intercooled making about 14 lbs of boost. Works good for me.

[lakesmodified]

[QUOTE]Originally posted by 058:
[B]Lakes, I set my .030" over 460 with .022" top ring and .016" second ring. JE pistons 8.4 to 1 C/R Banks twin turbo/intercooled making about 14 lbs of boost. Works good for me.
Well, what do think I should do now? I know have a new set of Speed-Pro rings that I set-up at .028 and .022 per J&E's instructions.. Too much gap? I really would hate to put this thing together and have a huge amount of blow-by.. CONFUSED!!!

[hellman2u]

Originally posted by lakesmodified:
[QUOTE]Originally posted by 058:
[B]Lakes, I set my .030" over 460 with .022" top ring and .016" second ring. JE pistons 8.4 to 1 C/R Banks twin turbo/intercooled making about 14 lbs of boost. Works good for me.
Well, what do think I should do now? I know have a new set of Speed-Pro rings that I set-up at .028 and .022 per J&E's instructions.. Too much gap? I really would hate to put this thing together and have a huge amount of blow-by.. CONFUSED!!!
if its a je piston they give you a small amount of cushion , but it depends on distance from top of piston to the first ring , if they did this piston for you as a blower piston listen to them. If the piston was done as as aspirated listen up even more. they need the distance to dissapate the heat , but also gives you a little area to build a carbon cushion, to speak. i run their piston for my combo with my own build #, and have had great luck . no massive blow by. other factors go into place also ,like w/or w/ nitrous and simple things like water temp,how much timing ,how fat are your carbs, they all go into play. good luck . these guys do pistons for some dudes with unlimited checkbooks , heed warning, listen up Jim

[wsm9808]

I set mine at .030 top ring and get nervous at anything less in a blown marine engine. Your gap is only at .030 when the engine is cold. As temp in the chamber,pistons,oil,rings,etc starts to climb the ring gap closes due to heat expansion. Extreme power equals extreme heat and the hotter things get the more gap you need to have to allow for more heat (HP=heat).
If your gap is too tight the ring ends will butt together and can cause so much friction that the rings can actually stick to the cylinder walls when the piston stops at TDC. When this happens rings will gall, break and can even pull the top of the piston off.
The ideal ring gap is one that just closes to zero at peak combustion temp, but since that can vary widely on a lake boat, it is best you give your self a safty margine and let the pro stock racers worry about squeezing at an extra HP or two from running exact minimum clearances.

[058]

Lakes, I built my engine about 3 years ago when these specs were the thing to run. Since then a few things have changed like second ring gap: more is better now, since the 2nd ring is mostly a scraper ring the thinking is to run more gap than previosly thought so that no pressure is built up between the top and 2nd ring, Too much pressure will unseat the top ring at higher rpm. If your top rings are gapped at .028" and the 2nd is at .022" I would run it as is. I have run as much as .031" top ring because thats all I could get for a 427 FE Ford. [Oddball size and thickness] so not many rings sets to choose from. That engine ran good and is still running today. Although it wasn't my first choice for rings as I had been thru 3 or 4 sets before I found that set I'm running now. One set had .039" end gap/top ring, they were returned.

[lakesmodified]

Gentlemen, thanks for all your input.... Seems like the best thing to do here, is go ahead and run the gaps that I now have... .028 top, .022 2nd.. Again, thanks for all the help... Hope to have this thing back together within a few days... I just have to stop working the overtime at work... Ivan