The gn guys upped the compression to 9.5 on some of the motors, but that was for big turbos, loose 9/11 converters, and a v6 so it needed some bottom end help.

I'm like Jerry and the majority 8:5 to 9:1 is about max.

 

Agreed... I used JE exclusively... and for FI either the Total Seal rings or JE's file fit. If you order pistons with standard size rings (versus metric) you'll save a few bucks there.

... and I wouldn't go with anything higher than .054 head gasket thickness.

Bill

 

JE's are nice, total seal or hellfire rings, and thinner head gasket will not only be stronger but in most cases better quench too. If it was me I would go with a 9:1 motor, Im not willing to change pistons in my setup to the best I can get it is 9.3:1 by going from 62cc combustion chambers to 71s.

 

What material type for the rings? I see chrome, plasma-moly, moly, and iron.

 

8.5-9.0 on a DD 408. The 408 will produce plenty of low end. Diamond pistons are heavier in most cases but they have revised their design recently and using a narower wrist pin and have lightened the pistons by 40-50 grams in most cases. But you can't go wrong with JE pistons.

 

I would go with Iron rings the others are harder and may last longer, but take longer to get to fully seat and seal. And being harder, might be more brittle and prone to breaking with detonation. That just my own theory though.

 

Putting a final list of parts together here:

https://www.performancetrucks.net/fo...21#post3493021

 

Plasma moly and chrome moly rings are the norm and iron second rings. A regular iron ring doesnt have the durability to last in a compression ring configuration. There is a reason why they are no longer used as a compression ring much less on a high boost application. Im no engine expert but over on tech I havent seen ANY of the big engine builders use a stright iron ring for the compression ring.

 

So between plasma and chrome moly, is there much of a difference?

 

Mine are plasma moly 1.5 top ductile iron 1.5 second and low tension 3mm oil ring and they are for nitrous/high boost app so take it for what its worth