I am building a 427 big block race engine ( forged pistons 12-1 comp, H beam rods, forged crank) and am going to squirt it with a 200 shot of nitrous.I would like to know what the piston ring end gap would be for both the top and second ring? I have heard differing opinions. Thanks! Bill napa219

i'm probably wrong but if i remember the general rule of thumb was .007" x bore diameter

It depends on what kind of ring? Childs&Albert? Speed-Pro?

Childs and Albert like .004" per inch of bore for N/A applications, i would assume this is why they seem to last longer than speed pro rings?

I dont run nitrous, but im gonna say .006"-.007" per inch of bore so that is gonna put you .026"-.030", in a nitrous engine if it was me i would run a gap around the same as the top due to the increased cylinder pressure from nitrous and this will help stop pressure from getting stuck inbetween the top two rings, also an accumulator groove would be a must in my opinion with nitrous

I would also run anti detonation grooves above the top ring with a nitrous engine

Check with piston and ringmakers as i dont use nitrous, what i stated is my .02 cents

also what rings are you using, i've heard nothing but good things about hellfires

I am using speed pro rings and the bore is 4.28 Thanks. Bill napa219

I have just freshened up a customer engine that uses a 250 shot. I originally gave the top rings (Perfect Circle moly on SRP's) 0.007" per inch and there was evidence of the ends touching. This time around I went to 0.008" per inch. This was a 4" bore so the gap was 0.028", now 0.032". The ring seal and leakdown was perfect with the big gap.
JMHO