File Fit Ring End Gap Specs on Street Motor ?

File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 04:18 PM

I'm getting ready to file fit the rings on my 440 street motor for my sig car and wanted some input on the ring end gap. Most of the tech articles I've read seem to want .004" per inch of bore for the top ring and .003" per inch of bore on the second ring. With a finished bore of 4.350 this works out to .018" for the top (rounded up from .0174) and .013 for the second. The pistons are forged Diamond units made from 4032 aluminum which has 15% silicone added to reduce expansion by 15% . The piston to bore clearance is .0045 as per Diamonds recommendation. The motor will be street driven with NO power adders and a max rpm of around 6,000. Any input would be appreciated. Thanks.

Posted By: moper

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 04:42 PM

What kind of rings are they? (brand...) I would use the ring manufacturers spec, with some modifications..lol. I run the tops at the "4 per inch of bore" rule and round up. So 4.355" would get an .018" top ring gap. Unless the piston requires differently. Diamonds don't take anything sprecial. I also run and extra thou per inch of bore on the 2nd ring. A lot has changed in the understanding of how rings work, and the 2nd ring with a larger gap can make more power and run cleaner.

Posted By: MR_P_BODY

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 04:47 PM

Quote:

I'm getting ready to file fit the rings on my 440 street motor for my sig car and wanted some input on the ring end gap. Most of the tech articles I've read seem to want .004" per inch of bore for the top ring and .003" per inch of bore on the second ring. With a finished bore of 4.350 this works out to .018" for the top (rounded up from .0174) and .013 for the second. The pistons are forged Diamond units made from 4032 aluminum which has 15% silicone added to reduce expansion by 15% . The piston to bore clearance is .0045 as per Diamonds recommendation. The motor will be street driven with NO power adders and a max rpm of around 6,000. Any input would be appreciated. Thanks.

I tend to use the manufacturers specs but now days
I open the second ring gap up a little larger than
the top.... reason is, if the pressure got by the top
I dont want to try and hold it in and cause ring
flutter on both rings

Posted By: maximum entropy

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 04:48 PM

Quote:

What kind of rings are they? (brand...) I would use the ring manufacturers spec, with some modifications..lol. I run the tops at the "4 per inch of bore" rule and round up. So 4.355" would get an .018" top ring gap. Unless the piston requires differently. Diamonds don't take anything sprecial. I also run and extra thou per inch of bore on the 2nd ring. A lot has changed in the understanding of how rings work, and the 2nd ring with a larger gap can make more power and run cleaner.

larger second ring gap has been shown to actually improve top ring seal. it allows combustion gases that have leaked past the top ring to escape past the second, preventing top ring flutter. also, a little too big is way better than a little too small. if the ends ever butt, you've got trouble.

Posted By: Classof70Chally

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 04:55 PM

The rings are Total Seals and they recommend .0045 per bore inch on the tops and .0035 on the second. This is for a "street/strip" application. Using those numbers the gaps come out to .020 (rounded up) for the top and .015 (rounded down) for the second.

Posted By: Cab_Burge

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 04:59 PM

I wouldn't take a chance on the ring end gap with the constant changing of the pump gas quality we get now, I would and do use .020 to .024 on the top and .022 to .026 on the second ring, as already said it is way better to have.002 to big than .0001 to small when it comes to a hot summer day and a batch of bad gas pulling a long hill

Posted By: Classof70Chally

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 06:03 PM

Okay, so if Total Seals specs show .020 for the top then maybe go .022? But they show a spec of .015 or .016 for the second then you would go .022 to .026 ???

Posted By: maximum entropy

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 06:06 PM

yes. and i'm VERY surprised they did not recommend a bigger second ring gap. almost everyone does now.

Posted By: MR_P_BODY

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 06:13 PM

Quote:

Okay, so if Total Seals specs show .020 for the top then maybe go .022? But they show a spec of .015 or .016 for the second then you would go .022 to .026 ???

I would set them at
top ring--- .020
second ring --- .022
also I dont set them loose.... try to be accurate with
your feeler gauges(vertical and square). Dont over
heat the engine the first few times you fire it up

Posted By: Classof70Chally

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 06:17 PM

OK. So it looks like I will split the difference here and go with .022" for the top ring and .024" for the second ring. Is there anyone here that sees a problem with those specs ???

Posted By: maximum entropy

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 06:20 PM

sounds good

Posted By: Anonymous

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 07:27 PM

Quote:

OK. So it looks like I will split the difference here and go with .022" for the top ring and .024" for the second ring. Is there anyone here that sees a problem with those specs ???

yes, i see a problem with it. first off, it's a street engine, secondly, it's completely N/A. follow the ring manufacturers specs for your application. round up to the nearest .001 for the gap recommended. the pistons you have, which are high silicon, not silicone, also have a built in balance groove between the top and 2nd ring. this will eliminate the need for such a wide 2nd ring gap.
if it were a racing engine i would have a different recommendation.

Posted By: maximum entropy

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 07:47 PM

Quote:

Quote:

OK. So it looks like I will split the difference here and go with .022" for the top ring and .024" for the second ring. Is there anyone here that sees a problem with those specs ???

yes, i see a problem with it. first off, it's a street engine, secondly, it's completely N/A. follow the ring manufacturers specs for your application. round up to the nearest .001 for the gap recommended. the pistons you have, which are high silicon, not silicone, also have a built in balance groove between the top and 2nd ring. this will eliminate the need for such a wide 2nd ring gap.
if it were a racing engine i would have a different recommendation.

that groove is called an accumulator groove, btw.

Posted By: Classof70Chally

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 07:51 PM

OK, thanks Dram. Yeah, the pistons do have a balance groove between the top and second ring lands. You're right, it's silicon (typo). Using Total Seal's spec's and rounding up, I get .020 for the top and .016 for the second. They recommend a multiplier of .0045 for the top ring and .0035 for the second. It will be strictly a street cruiser with maybe one blast

down the track for a time slip just to see what it will do. I appreciate everyones input on this. This is my first 'file fit' ring job and it's nice to have the accumulated engine building knowledge that is available here on this site.

Posted By: Anonymous

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 08:02 PM

the 2nd ring will never see the same amount of heat as the top ring, especially in a street application. that combined with the accumulator/ channel/ groove, is the reason for leaving the 2nd ring a small amount tighter in the bore. (less expansion}

that groove is called an accumulator groove, btw.

it's also called a pressure balance channel, a pressure balance groove and a few other things. different names from different piston manufacturers.

Posted By: maximum entropy

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 08:44 PM

there are definitely numerous ways to skin that cat. the tight gaps concern me. .013 on the second is really tight. be very careful to get the gaps perfectly square ( as you always should ), and don't overheat that thing. i have a very similar build in my street strip car, and i'm at .022 top and .024 second, and have as near zero leak down as a conventional ring engine can have. i seriously doubt one could find a measurable difference in leak down between .013 and .024 on the second ring. the extra silicon, btw, makes for a much more scuff resistant piston. good choice.

Posted By: Classof70Chally

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 09:22 PM

I just finished the file fit and I went with .020 on the top and .016 on the second. It went well but it doesn't take much of turning the 'wheel' to get the rings filed down. It took me longer to 'deburr' the ends than it did to do the actual filing. I hadn't thought about the reduced scuffing of the piston but that's a plus. I originally went with the silicon added pistons for less expansion and a tighter fit to reduce cold piston rattle on start-up.

Posted By: mopardamo

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 10:34 PM

Hello Dan,

Apparently he thought you needed a lesson. He funny today.

"that groove is called an accumulator groove, btw."

Damon

Posted By: maximum entropy

Re: File Fit Ring End Gap Specs on Street Motor ? - 02/03/09 10:48 PM

Quote:

Hello Dan,

Apparently he thought you needed a lesson. He funny today.

"that groove is called an accumulator groove, btw."

Damon

somebody gets my jokes. yay!