Ok I have a 1994 F150 originally had a 302 in it. I built the motor up to a very high performance 347 stoker, full roller motor, custom ground cam (same center line for computer). I have 36# injectors in it but it was running very rich and was getting very very poor gas mileage. I understand that i am not going to get great mileage but I'm talking i was getting about 2 gl/mile and yea I typed that right. So I put the stock injectors back in which is seriously holding this motor back. I was wondering if the computer will automatically adjust the fuel curve for the 36# injectors or if I need to call Motorvation. Thanks for any help.

 

your problem is most likely the MAF. It's calibrated for the stock injectors, the computer doesn't know what injectors are there and it doesn't really care, anytime you increase injector size, you have to replace/recalibrate the MAF.

Try here: http://www.promracing.com/

They can either recalibrate your stock MAF or you can by a new, larger one with it calibrated correctly. (I'd do the second choice, larger MAF)

Or, you can give this a try:

http://www.mass-air.com/Products.htm

This little box will "fool" the PCM into thinking you have a new MAF and should work with your 36# injectors with the stock MAF.

Keep us posted.

 

what are the motor specs and what are the EXACT cam specs...?

what is the vacuum in inches at idle...larger injectors are more neccesary if you plan to do full throttle runs....idle and part throttle the stockers will work just fine to get a basic tune...

you also need to know what your timing is at...and is the firing order on the 347 cam the same as the original 302...if it isnt you need to firing order of the injectors....

you have more than one issue here

 

I don't know what the vacuum is at idle. The exact engine specs are as follows - 3.4 inch stroke, SRP pistons, eagle rotating assy, 10.9 to 1 compression, 52 cc combustion chamber, high psi oil pump, full MSD ignition. Cam specs are as follows - Custom Cams Inc., center line is the same for computer, duration @ .050 211 intake 215 exhaust, Lobe lift .277 intake .300 exhaust, Valve lift 1.6 rocker .443 intake .480 exhaust, Lobe separation 112 deg in CL 107, firing order is same as original.

 

oh yea i have .450 gap on plugs and base timing is at 16 btdc

 

the motor is not a crate motor it was custom built to run with the stock computer but i just have to get all the other stuff around the motor to make it run right and show its true potential.