i'm thinking about builting my first motor soon (a 350 i hope) but i want to know what you guys think about the gap for piston rings

when i had someone build my 305 for me i told him i was thinking about putting NOS on it so he said he gapped the rings for 150 shot well after i put 2,500miles on it i still had some blow-by and i wanted to know what you guys think about it. i was told about .030 (i think) was about where you should gap them. also when i install the rings i have to make sure not to have the gaps lined up right?

 

Ring gap will depend on the application, piston type, and ring material. .030" sounds pretty large unless the pistons are forged and you're really boosting it. I have no experience win NOx, so I can't say if the gaps would be similarly opened.

When installing rings, it is good practice to stagger the gaps of the compression rings about 120°, and the rails and expander joint of the oil xontrol ring assembly. Try to keep all the gaps away from the area of the piton pin ends. The rings will move in normal use, but starting them out in a staggered arrangement is the best you can do.

 

some of my manuals show where to position each ring gap, and i follow it. i've built a couple of engines without any sort of pattern to the gap arrangement except for not lining them up and have never had a problem. i to have no idea about power adders, but i'd follow the specs of the piston maker or the manual if stock. i'd doubt that power adders generate more heat, the reason ring gaps are opened up, or closed up i believe depends more on heat transfer through the piston and to the ring. if blow by was a concern i'd run a ZGS c&a ring and open the gap up on the top ring. good rule of thumb to follow on end gaps is .003-.004 per inch of bore.

 

well from all the stuff i have read on the net about NOS is that it burns hotter and it you put a 150 shot on a stock motor you can have the rings melt to the cyl. wall cuz they expan thats way having move of a gap lets then expan more then stock and they won't mess up the cly wall. only problem with that is you can get more blow-by then normal (we all know every car has blow-by)

also i have heard if you dry set the rings int he cyl. that the brake in time is about 500miles other then the 3000 miles when you wet set them.... is that true as well?

 

ok nox generates more heat, i wondered about that when i was typing it. still it comes down to the psiton transfering the heat to the ring. piston design, ring location, and thickness would also be a major factor. i'd bet a dollar or two that proberly tuned stock engine would with stand a 150 shot for quite a while with no problems. the key word there is tuned. run nox without the proper controls and tune up and you'll break parts. never really leaked an engine to know, but i'd also bet another dollar or two that rings seat within 30 minutes with proper break in.

 

Except for the plasma coated chrome mollys. I've known too many people that had troubles getting those "high dollar" rings to seat, they take a bit longer than regular rings.

 

Yep thats what i have. speed pro i believe is who made them.

 

Just gap them to what the piston maker has in their manual. I used .026 and .022 but I plan on running about a 300-350 shot.

 

A ring gap of .030 is huge. On my old nitrous race car I set the ring gaps at .025 for the top and .020 for the second ring. It ran with about 200 or so shot of nitrous.

On my most recent endeavor, a 383 street bound engine I set the ring gaps at .020 for the top and .016 for the second ring. I used the Childs and Alberts plasma moly rings for both engines and when I disassembled the motors the rings looked great. THe bores also looked good. I wish I had performed a leak down test prior to disassembling the 383. Oh well its being rebuilt as a blower motor.

Just follow the ring manufactruers reccomendations and you should be fine. THere are other tried and true methods of ring gap like what ede said earlier. Good luck...