2G Screwed Up Ring Gap

[Mham2k]

In the process of filing my ring down, I mean to do .020 top and .024 bottom based on some recommendations and calculations.

I screwed up a filed the top to .025, i'm leaning towards buying one new set of rings.

Should i buy one new set or open up all the gaps?

 

[motomattx]

Buy a new set.

 

[Mham2k]

Buy a new set.

Thanks

 

[jakelandry]

There are several piston manufacturers that recommend bigger top gaps than bottom. Look into it. I’ve yet to see any evidence that one method is superior to the other.

 

[1990TSIAWDTALON]

I run .024 top and .028 middle on my motors. No smoke, good seal and plenty of room to expand under high (40 lbs) of boost.
Just FYI.

 

[Mham2k]

I run .024 top and .028 middle on my motors. No smoke, good seal and plenty of room to expand under high (40 lbs) of boost.
Just FYI.

Really? I'm looking for an HX40 now and will be running high boost.

Pistons are Wiseco HD's in a 6 bolt.

How long have you been running them like that?

 

[1990TSIAWDTALON]

Since brand new rebuild this summer. She runs really good and not a single puff of smoke on initial startup or anything since then and I have been thrashing it somewhat since I am tuning it. So around 6 months or so on an HX40 on gate pressure of 33#'s.

 

[Mham2k]

Since brand new rebuild this summer. She runs really good and not a single puff of smoke on initial startup or anything since then and I have been thrashing it somewhat since I am tuning it. So around 6 months or so on an HX40 on gate pressure of 33#'s.

Hmm.. Maybe I will try some larger Gap's...

 

[1990TSIAWDTALON]

Here is MY build sheet.......you are welcome to use any or none of it. I didn't get the car running until summer even tho this build was DONE in March.

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[Mham2k]

Here is MY build sheet.......you are welcome to use any or none of it. I didn't get the car running until summer even tho this build was DONE in March.

You must be logged in to view this image or video.

Thanks

 

[1990TSIAWDTALON]

Anytime!

 

[97egl]

There are several piston manufacturers that recommend bigger top gaps than bottom. Look into it. I’ve yet to see any evidence that one method is superior to the other.

The reason for a larger bottom gap is ring flutter. If the blow by gasses get stuck between the 2 rings rather than blowing by the 2nd ring as well it can un-seat the top ring. This is usually only an issue in performance engines which is probably why you get different ring manufactures stating different ways of doing things.

Edit- To the OP: also as to your issue of the ring gap being .025 you could try the ring in the other cylinders and see if it measures any less. The cylinders are all slightly different sizes but I really would not worry about .025 top gap. My person opinion put your top gaps at .024 and the bottom at .028 (I have my engine at .022 top and .026 2nd ) you'd much rather have a tiny bit more blow by than have the rings expand too much and butt against each other resulting in a scored bore and/ or cracked piston.

 

[Mham2k]

The reason for a larger bottom gap is ring flutter. If the blow by gasses get stuck between the 2 rings rather than blowing by the 2nd ring as well it can un-seat the top ring. This is usually only an issue in performance engines which is probably why you get different ring manufactures stating different ways of doing things.

Edit- To the OP: also as to your issue of the ring gap being .025 you could try the ring in the other cylinders and see if it measures any less. The cylinders are all slightly different sizes but I really would not worry about .025 top gap. My person opinion put your top gaps at .024 and the bottom at .028 (I have my engine at .022 top and .026 2nd ) you'd much rather have a tiny bit more blow by than have the rings expand too much and butt against each other resulting in a scored bore and/ or cracked piston.

Thanks, when i put this ring in cylinder 4 is is slightly smaller, bites a little on .24 but can't fit .25.

I will probably do that.

 

[motomattx]

My point in suggesting replacement is that you want consistency across your ring packs, you want all upper rings the same gap, all second rings the same gap etc... will that few thousandths ruin your engine? probably not, but its just not good practice to allow things like that.

 

[97egl]

My point in suggesting replacement is that you want consistency across your ring packs, you want all upper rings the same gap, all second rings the same gap etc... will that few thousandths ruin your engine? probably not, but its just not good practice to allow things like that.

If he does .024 on them all and puts the one in cylinder 4 so it measures between .024 and .025 I wouldn't consider that a bad practice. I'm assuming that you are saying not to do 3 of them .020 as the OP originally planned and leave the one at .024 and I would certainly agree with that as the compression would differ slightly. In my opinion I would suggest the OP go with the .024 ring gap on all cylinders. .020 will probably be ok but .024 gives you a little extra room in case of running hot or other circumstances that the ring gap might close at .020. <----- This is all just my opinion tho.

Someone out there with more knowledge on boosted engine ring gaps would be great to have chime in on this. Most my experience with ring gaps comes from N/A endurance racing. I've had ring gaps close up and it's not pretty. Added a few thousandths more to the gap and the same situation (Running 240 degrees for several laps to finish the end of a race) and haven't had any issues with the gaps closing and busting pistons. That's why I'm opinionated of adding enough gap.