i wanna put nitrious in my 383 TPI, what size combustion chambers should i have? would it be the same an a non-NOx combustion chamber or is it different?

PS: i havent decided on heads yet so i cant tell you my compression ratio or my setup. can i still be helped, is there a general rule?

thanks
Gramps

 

It's better to use nitrous on a slightly lower CR motor. Ie, not when you're already pushing the envelope.
Are you going to be using the nitrous as a small shot (150HP say), and just once in a blue moon, or like 200HP, and every time you run the car - ie, a track only car?

If it's just once in a while, not a huge shot, I wouldn't sweat it. Just keep the CR below 10:1 on iron heads and you should be ok.

If it's a big shot, i'd keep the CR a bit lower, use a bigger exhaust valve, and or a nitrous/blower cam with more exhaust duration, open up the ring gaps like crazy, use head studs, etc.

 

if u should keep the compression below 10:1 on iron head what about aluminum?

 

its gonna be a street/strip, so ya once in a blue moon, and i think that 150 will be plenty. i already thought about getting a cam with a longer exhaust duration thatll still give me the power i want on and off the bottle. i also know about the CR being less than 10:1, but im wondering about the combustion chamer of the heads. like a 58cc chamber or a 78cc? is there some sorta rule that i should follow for the street/strip application?

EDIT: why shouldnt i be running aluminum heads?

 

No, you can run AL heads, I was just saying keep it below 10:1 on iron. A bit higher on AL is fine. Just don't be running the ragged edge on pump gas, then use nitrous. That pushes the envelope eh? An ignition module with the ability to pull timing for the nitrous might be nice, but if you're only going to use it once in a while, just pull over and knock off 4* base or something, and then hit the nitrous. Oh wait, TPI, not sure how they do the ignition. It's all computer controlled so... Just remember you'll want to pull a bit of timing for the nitrous. Also probably want a cooler plug. Just a bit.

The 58cc vs 76cc chamber - well, depends on the pistons etc. Whatever will give you the correct CR you want for the motor.
If you're using flat tops in a 383 it'll probably be the higher end of the scale, 76cc or so, to keep from having sky high compression.

Yea, a normal split pattern cam with ~6-8* more duration at .050" on the exhaust side should work just great.

 

thanx sonix ill take your recomendations in mind.

 

N2O is an interesting animal WRT to tuning:
- you do not want to detonate while spraying at all, that’s the kiss of death for engine parts
- Timing doesn’t make as much of a difference as it does NA
- Compression doesn’t make as much of a difference as it does NA

In other words, it’s not that timing or compression is bad when spraying, but it doesn’t gain you want it does NA, and if the thing starts detonating things get ugly MUCH faster… put 2+2 together, and it makes sense to go more conservative with that N2O motor than a comprable NA setup.

 

If your car is running now, just put the nitrous kit on it and run it the way it is, either a 100 or 150 shot is fine on a stock motor.

I would do this before you start spending money on new heads, 'cause if you have the stock tranny, it's gonna up the ghost before you will need the cylinder heads.