A friend of mine has a 96 ram air firebird (stock with 150 shot of NOS dry kit). He stopped by and told me he ordered 42# injectors which I think are to big because I ran those on my 511 rwhp mustang. He also said he was told he will not need a new mass air. I am just learning about GM's so sorry if these questions sound stupid.

1. Do you GM guys have to have your mass air calibrated for your injectors like us Ford guys?

2. Wont his car run terrible stock with 42# injectors? If I put those in a stock mustang it would be WAY rich.

Thanks,

Brent

 

If he's running the NOS dry kit for the LT1 (NOS part 5176), and it is a relatively stock engine, you don't need larger injectors. The NOS kit bumps the fuel pressure up to 85-90psi when you spray, to increase the fuel flow through the stock-size 24# injectors. Where you get into trouble is that the stock RP injectors are not happy with that high a pressure and can lock up, so you need to get a set of 24# SVO's.

If you were to change the injectors to 42#, it would throw the NOS jet sizes completely out of whack. But if his car is making enough HP to require that size injectors, he needs to alter the computer (PCM) programming with the new injector flow constant and offsets. We don't have to alter the MAF calibration, we just need to put the correct injector size into the PCM. If he's making enough HP to require 42's, he should already have a custom PCM tune.

If he put 42's in without programming, it would not run at all. If he puts the right data in the PCM, it will probably run fine, with a very low duty cycle. Might have some problem on idle, due to the inability of the large injector to turn down to the sub-1mS pulse widths required at idle.

The stock 24's will easilly support 400 flywheelHP (some people have run them out to 450HP, but I wouldn't). Prorate up from there..... 30's for 500HP, 36's for 600HP, etc.