FrontEngineDragsters.Org Forum

Technical => Matt Shaff's Engine Shop => Topic started by: George on January 19, 2016, 05:07:38 PM

Title: Piston ring end gap.
Post by: George on January 19, 2016, 05:07:38 PM: Matt, what would be your preference for piston ring gap? Our combination is a fully filled Dart LIL M with Dart 230 cast iron heads running with no coolant in a FED. It's a 6:71 with a Bug running alky thru hat nozzles only. It's wet sump system with a System One remotely mounted so I run 10 quarts and we will be adding a Accusump to add even more oil ( cooling ?). It's been together for 2 years and have had no ring or piston (Venolia) issues. They are a 16-16-316 ring package. It's time for a freshening . I'm thinking we can tighten up the gap that is now at .026 .
We run almost all 1/8 mile and don't spin it more than +16%

Thanks . George
Title: Re: Piston ring end gap.
Post by: Frontenginedragsters on January 19, 2016, 07:07:42 PM: Hello George:
All of your parts selection sounds great.
Is the engine 4.125 bore? Then .026 sounds right with a blower. I would not go much tighter.
I would run the Total Seal AP top ring. Its stainless and works great with hard aftermarket blocks.
We have been changing our procedure for honing the aftermarket blocks.
Call Total Seal if you have any questions. I call them and Sunnen from time to time to make sure we are doing the right thing.

Matt
Title: Re: Piston ring end gap.
Post by: Paul New on January 19, 2016, 07:14:20 PM: I agree with Matt no tighter than .026! A little to much gap will not hurt your performance.... but a little to tight could ruin your day
Title: Re: Piston ring end gap.
Post by: George on January 20, 2016, 05:26:41 AM: Thanks guys. The block measures 4.133 to give the piston .008 clearance. Can I buy just the top ring somewhere?
Title: Re: Piston ring end gap.
Post by: Paul New on January 20, 2016, 07:59:44 AM: Alerly Child's can sale you what ever you need 1-661-702-1999
I would open up your ring gap a little 4.133 X .0065-.007= .0268645-.028931 I would do .027 if it was mine.

I think Matt is saying to call Total Seal and buy their rings though.
Title: Re: Piston ring end gap.
Post by: George on January 20, 2016, 08:03:30 AM: Thanks again. I will do some checking.
Title: Re: Piston ring end gap.
Post by: dreracecar on January 20, 2016, 08:16:37 AM: Save your money and dont go with the the TS

Once the standard rings heat and expand the gap closes off to almost nothing anyway. Couple that with the piston speed during stroke and the other rings on the piston there isnt anything going past them.
On a asperated engine where you require the piston to draw air into the cumbustion chamber, then OK, every little bit helps, But a blower fills the chamber and that extra draw (however minute) is meaningless.
Akerly & Childs Dura-Moly ring package is the best bang for the buck
Title: Re: Piston ring end gap.
Post by: masracingtd1167 on January 20, 2016, 11:53:03 AM: I don'd think there is any magic in running tighter gaps . My motor is not supercharged and I run .028 and 0.30 end gaps and it always leaks down at 2 to 4 percent . On my sons big block with nitrous he runs the gaps at .040 with no issues .
Title: Re: Piston ring end gap.
Post by: George on January 20, 2016, 01:45:15 PM: Quote from: masracingtd1167 on January 20, 2016, 11:53:03 AM
I don'd think there is any magic in running tighter gaps . My motor is not supercharged and I run .028 and 0.30 end gaps and it always leaks down at 2 to 4 percent . On my sons big block with nitrous he runs the gaps at .040 with no issues .

My concerns are in the fact I run a filled iron block and iron heads with no coolant and looking to see what builders are setting the gaps at for this kind of build. I haven't had any issues but I'm always looking to learn something. Thanks. George
Title: Re: Piston ring end gap.
Post by: coupemerc on January 20, 2016, 02:17:41 PM: I would recommend going with the ring manufacturer's recommendation as a minimum. On my deal I just multiplied the recommended gap/inch of bore by the bore diameter and rounded up to the nearest thousandth of an inch. That was the minimum number I filed to. I used zero gap C&A second rings on my old blown alcohol engine and I can't say that they made any more power but they certainly give you real low leak down numbers when hot.
Title: Re: Piston ring end gap.
Post by: dusterdave173 on January 20, 2016, 03:13:52 PM: I think he was saying Total Seal because they have widest selection of All types and best tech anywhere--I get all kinds of odd bore/ring combos from them --all std style stuff I Never ever use the Gapless that you are talking about--you are right Gapless rings are Voodoo unless you run on dirt track and eat dirt by the pound--in that application it keeps fresh ups a little further apart but otherwise I hate them--Leak down they look great on the dyno I have never seen a gain from Gapless
Title: Re: Piston ring end gap.
Post by: dreracecar on January 20, 2016, 05:42:44 PM: Quote from: George on January 20, 2016, 05:26:41 AM
Thanks guys. The block measures 4.133 to give the piston .008 clearance. Can I buy just the top ring somewhere?

My combination was 4.135 because thats what the 400 block cleaned up at and when that block went away I bought a new Donovan alu block and to save money I had them install used sleeves that also cleaned up at 4.135. Just started with a 4.140 ring package and then filed to fit.
Title: Re: Piston ring end gap.
Post by: Frontenginedragsters on January 23, 2016, 06:41:29 PM: The Total Seal AP top ring is not gapless. Its stainless and works good on hard cylinders.

Matt