Just curious what you guys with Speed Pro Plasma Moly rings run for ring gaps? My last rings were never gapped, just put on right out of the box (no I didn't do them). I however want to do it right and gap them. Is this info available from the ring or piston manufacturer? I run Speed Pro forged pistons if that helps at all! Thanks

Bill

 

smoknz,
I am not sure baout the gap on an FI setup, but generally i know when determing piston to wall clearance on forged motors with FI, the manufacturers generally want to see a little looser fit to allow for the extra expansion associated with the higher chamber temps from boost. i imagine that the ring end gap on a street driven car thats not going to be inboost all the time should be a little wider then standard.. i think this may be one of the reasons some people have had trouble with excessive ring wear.. once the boost comes in the rings and pistons get very tight this will certainly bring about a higher wear environment for the rings. i am going to go with the recommendation of total seal when i am ready to file fit my rings. hope this helps.

also, how do you like the speed pro forgings? I am using a set of them myself the -21cc 30 over bores, they are certainly heavier then the 2618 forged ross pistons i used on my previous NA motors, but have some pretty beefy ring lands on them. i figure for boost they will hold up nicely, but I would not want to rev them very much as the extra weight would put some serious loads on the con rod bearings. anyways, just yackin.

Chris

 

I've run those pistons for almost 3 years now with no problems. The machine shop that did my block work and mounted those pistons said they weighed so close to the stock pistons that they didn't need to be ballenced. So that is the way I ran them. I can't imagine they are to heavy, guys spin the stock shortblock upwards of 6500! Never had any problems, and all the bearings looked perfect when I took it apart this past winter. I have no complaints about these pistons!

 

Bill,
I would gap them according to what speed pro recommends for a supercharged setup. If I remember correctly, mine were gapped at .025" top, .020" second. Never had a problem with the rings btw.

There is also a new theory about gapping the second wider than the first, helping out the top ring from flutter. Don't know much about that.

 

For my 4.030'' bore nitrous engine I want to put about .03''-.035'' ring gap at the most.
If I was doing FI I would leave them .025'' or more if I were to run up to 14psi.
When I get a chance to tare into my 3.4L (3.62'' bore) I was going to run them both .025'' for med boost turbo I'm working on over here.

 

IIRC I gapped them at 0.26-0.28

Stock is around 0.22-0.24.. I added 4 more to account for boost.

 

I second that.

Mike