So my piston rings are gone from the last owner spraying a 125 shot through it a couple too many times. So now comes the time to rebuild and the parts list will go like this.

408 sb
750 double pumper
110 holly mech. fuel pump
ported 997 heads
forged pistons and rods
cast steel crank
all with a 10 to 1 compression ratio
RPM edelbrock nitrous kit "up to a 200 shot"

So how much nitrous could I get away with safely?

 

I'd put a 150 through it, you shouldn't have any problems if your fuel/timing is set accordingly...

 

408 CID? Start at 150 and tune your way up to 200. I seriously doubt a 125 shot used correctly hurt that or any >300 CID motor.

 

400 + 40 over = 408

Well the motor itself has only 30,000 on the rebuild. I know for a fact that the guy used nitrous alot and the pistion rings are well shot so i just put one and one together.

 

well if my 2.8 can take 150, your should be able to. but i would take car of your rings before to much nitrous. im assuming its a wet shot, but i dont think you would have a prob with 150-200.

 

put a nice gap on the rings and work your way up to a 225-250 shot.
a 150 shot on a stock motor should last a very long time if its tuned correctly with enough fuel and some timing taken out.

 

we all know what a 408 is...he was just saying that anything over 300 cubes should be find with a minumum of 125 shot. It may have shot the rings, but only because the tune was off, not from the nitrous itself...if they are gapped properly and the A/F ratio is good 408 cubes can take 200 shot all day, also provided the motor is put together correctly. im spraying 300 on a fully built 383..

 

Well would the air flow ratio of a 997 cast head with it being ported to
2.02/ 1.6 be good enought for a 200 shot?



Also is there any good motor building sites for small block chevys that will have alot of info for things like torque specs and ring gap steps for engine building?

 

I would personally install forged pistons for nitrous with .007-.010 sidewall clearance and run around .021 on the first ring gap, or better yet, run zero gap rings.

 

my opinions-
put the nitrous idea on hold and get some decent heads first.

up to a 100-150ish shot you can run a dang near stock ring gap. once you start going above that, open them up more. i think im running .028 top ring and .025 2nd ring. plans are to hit it with a 200-225 shot on stock LT1 pistons. this is probably a big gap for what im doing with the car, but its better to go too big than not enough.

 

Well i already have then nitrous on the car, and getting cylinder heads is kinda exspensive right now. I was just gonna do the bottom end right then get the heads next year and just drive it with the ones I have now. Also how would the car run with out nitrous if I had a larger ring gap? Like for example just driving around on the street.

 

you wont notice it.

 

ok, i think I will just put the larger gap on the rings and just drive it N/A until next year because i still have a nwc t5 trans in it. So i have to get a
G-forced trans and better cylinder heads and call it a day.