[ChevyThunder]

I have an engine I'm building
434 stroker
afr 210 cylinder heads
11:1 compression
JE pistons
Perfect circle rings
Street Motor

Both the rings and JE reccomend around 20 thou for ring end gap based off the charts I can find.

The machine shop reccomends I gap them to 32 thou and 35 thou. The only way I could match this on the chart was picking the highest level (race only supercharged/nitrous oxide) I am definatly not in this range.

Is there any reason why what the shop reccomends would be so much higher?
I do trust them as they have a good name in the area and haven't steered me wrong yet, however I would like to know if there is a reason why it would be so much higher before filing them.

I know the consequences of filing them not enough is much worse then the little blowby you get from going slightly over. I

[TorkMonster400]

There was a study done by someone maybe KB, I think Fbird posted it once about the end gap not even really being a big factor in oil consumption or something like that. What kind of metal are the pistons. I know that KB hyper pistons require a pretty large gap to keep top ring land failure from happening. I would call JE and give them the specs a see what they say, thats what I did with my KB pistons. I think mine was around 32 or something I can't think of it off the top of my head

[TorkMonster400]

Found it I think. This might help you a little

http://kb-silvolite.com/article.php?action=read&A_id=56

[techinspector1]

This is too important to screw it up. Get on the phone to JE. Be ready with all part numbers and your intended build and get a recommendation. Get the guys name and direct line that you talk to.
http://www.jepistons.com/dept/company/

[TorkMonster400]

What he said^^^^^^

[ChevyThunder]

will do... Unfortunatly I don't think I was given any part numbers for my pistons or anything but hopefully I can pull a part number or forging number off the bottom that will be useful for them. I don't imagine they make too many different 434 pistons.

Like I said I trust what the machine shop says as they are a high performance shop and build more engines in a year then I probably will in my lifetime, but I like to double check these things. Especially when they are so critical.

[TorkMonster400]

Thats kinda like saying the guy at Mcdonalds serves a million burgers a year, but I'm not taking his advice on one. Trusted Machine shop or not I would still call

[racecar100]

Many engines that we build with JE Pistons. We use .016 for top and .012 for second groove on racing gas or alochol. We build lots of 434 engines for dirt track late model and drag racing. The best 434 we build for drag is 4.88 on a 1/8 strip on one carb and no NOS.

[oldbogie]

Originally Posted by ChevyThunder

I have an engine I'm building
434 stroker
afr 210 cylinder heads
11:1 compression
JE pistons
Perfect circle rings
Street Motor

Both the rings and JE reccomend around 20 thou for ring end gap based off the charts I can find.

The machine shop reccomends I gap them to 32 thou and 35 thou. The only way I could match this on the chart was picking the highest level (race only supercharged/nitrous oxide) I am definatly not in this range.

Is there any reason why what the shop reccomends would be so much higher?
I do trust them as they have a good name in the area and haven't steered me wrong yet, however I would like to know if there is a reason why it would be so much higher before filing them.

I know the consequences of filing them not enough is much worse then the little blowby you get from going slightly over. I

As usual I buck the trend, since the top ring runs hotter than the second ring I reverse the typical recommendations and run the top at .005 inch for every inch of bore and run the second at .004 for every inch for a street engine on gasoline. I you're going to run nothing but E85 I'd recommend .001 inch less than this for the top two rings, because alcohol burns cooler than gasoline. If you're running a blower or nitrous add .0015 per inch of bore to those first numbers. If a competition engine add another .0005 per inch of bore to that.

For the oil rings I like to run .010 to .020 between street on gas or nitrous, blower and or competition regardless of bore. This end of the piston is pretty cool compared to the top ring

Keep ring gaps off the thrust surfaces which simply means put 'em over the pin axis. I align the top ring in the forward direction above the pin. The second ring goes to the rear above the pin. The top oil ring goes facing forward over the pin, the expander butts just to the side of that gap. The lower ring again faces to the rear over the pin.

Its most important not to run them too tight, if they expand more than planned for, they could butt together. If that happens, the ring wil be forced into the bore wall and will break apart gouging the wall and the piston as it disintegrates. I suspect your shop is just trying to crowd any potential warranty benefit to their side of the bill. The small amount more will not have any great effect on oil consumption or compression and will insure they don't have to go in and fix-it.

Bogie