Alright, I am going to be setting up the pistons tomorrow FINALLY!
But, looking at their guide sheet, they recomend for street, strip and circle track:
top ring~ bore x .0045
second ring ~ bore x .0055

So, with my 4.040 bore, its 4.040 x .0045 = .018" for the top and
4.040 x .0055 = .022" for the bottom.

But, I thought you were supposed to have the top ring clearance looser than the bottom... am I wrong?

Also, does this sound like good ring clearances for a 385 stroked LT1, hopefully pushin 440rwhp??? This is above all a daily driver, so I don't want any heat issues or whatever. But, this info is straight from mahle with the pistons I bought, the power pak ones.

So, any suggestions? Anyone set up their ring sizes with mahle pistons different from what they suggest? Its funny, cuz right at the top of the flyer is says " WARNING: tight ring gap clearances may cause major engine damage!" But, this seems pretty tight to me...

I hope someone can chime in with experience here before tomorrow morning!

Thanks!
Cody

 

There are different schools of thought on this, mostly race vs street app. I always go by the ring makers suggestion.

 

ok, I just dont want to set it up too tight and have issues down the road, ya know?

 

anyone else?? I want to get those fitted this morning yet.

 

I think that's excellent advice. Absent a good reason to do otherwise, that's what I would do.

Rich

 

well, I called mahle this mornin. After discussing my motor, and its intended use, we settled on .018 on the top, and .016 on the bottom. Seems kinda tight to me, but they assured me it would work just fine. They said I would have excellent scraping, and improved oil contorol as its a daily driver. So, I guess time will tell!!!

 

Okay, a few quick comments:

The first set of ring gap specs you cited, (i.e. Top ring = bore x .0045, etc.) sound prefectly okay for your 385 inch, daily driven stroker motor. If you're thinking they're too tight, then yes, you are wrong. They are definately too tight if you're thinking of running spray anytime on this motor, but they're good for a N/A street stroker motor with NO power adder.

Also, what makes this even more confusing, is that you ask if you're "wrong" thinking that the top ring gap should be "looser" than the second ring gap. That too is wrong, which makes the tech line advice you got to run the second ring gap at .016 under a .018 top ring gap also wrong! If you want to "tighten" up your gap specs, you might consider running a second ring gap say only "slightly" larger than the top, like say a .020 second ring gap under your .018 top ring gap. You better call that tech line back again tomorrow and confirm that they asked you to run a second ring gap tighter than your top gap. That is soooooo....... "old school" that it even hurts to think about that.

 

It's only "old school" depending upon who you talk to...the first ring see's much more heat and is going to expand more. With mahles presicion ring lands and tight clearances I would not be worried about ring flutter.

People also don't like C&A's ZGS rings, but I use them and love them...

Everything comes down to the application that it will be used in, this is a simple street motor.

 

hmm, so you think this should be good then machinist one?

 

The stock LT1 Mahle pistons and rings direct from the factory run a larger 2nd ring gap and it works extremely well.

I'd look into it a little more before deciding. We talked about this wider 2nd ring gap in the Advanced tech section about 2 years ago. The wider 2nd ring seems to be very very popular now-a-days.

So 2 years ago I started doing the wider 2nd ring gap and it seemed to work very well. I even undid a ring set that pro stock engine builder Terry Samakow filed for me and made the 2nd ring gap larger.

On a more recent engine assembly with Total Seal conventional file fit rings the instructions say to go tighter on the 2nd ring gap and now I'm so adverse to the "old school" that that I could not bring myself to doing as per instructions. (I went with the slightly larger 2nd ring gap...... .022" 1st, .023" second). See at least how mind gets stuck in it's ways. Ahhhhh!

Karl Ellwein
Ellwein Engines
http://www.karl-ellwein.org/EllweinEnginesHome.htm

 

NO NO NO NO NO

Do what the box said originally. The larger second gap is there to help top ring seal, since that's the only one that does seal. The second ring is just a scraper really.

I'm with Karl on this one. Go wider on the 2nds.

Bret

 

if its just a scraper, then why does the gap have to be looser on the bottom? The top one sees the compression and heat, so it would expand more, the second one is along for the ride... so how come the second ring should be looser? Im not trying to say your wrong, just looking for a quick education!

 

It lets the pressure that builds up between the top and 2nd rings out which helps the top seal better.

Bret

 

On the other hand, the second ring needs pressure to act as a scraper and control oil as is it's purpose. Just playing the devil's advocate

 

I think that is why mahle told be .016 for the bottom ring, so I get excellent oil control for a daily driver.