redlined4816

i have a 350 TPI with all of the intake from a 305, are they different size injectors? can anyone tell me what size they are and will stock LT1 injectors fit and what size they are

Todd80Z28

IIRC, 305TPI were 19lb/hr. The 350 was 22lb/hr, and LT1 got 24lb/hr. And, I'm pretty sure the LT1 injectors fit fine.

350TPI

Yes there is a difference in all 3 motors.350 TPIs have 22 LBers.The 305 has 19 LBs and the LT1 has the 24 lBs.I recently put in the 24 LBs in from an LT1 and the car runs better than it ever has.But i also had a chip burned to run the injectors and not be rich.I believe you will run very rich with 24 LB injectors with the stock 350 chip.

Damon

I'm with 350TPI on this one. If you still have the original 305 ECM and chip running it you're probably better off leaving the smaller 305 injectors in it for now- jsut to get you up and running. Reason is that the 305 chip THINKS it's still running 19lb. injectors. If you actually put 22 or 24lb units in it the ECM is probably not going to do such a good job running the engine. This is especially true if it's an earlier Mass Airflow style TPI system. MAF systems freak out pretty bad if you have a mismatch between the injectors and the injector flow constant programmed into the chip.

Regardless, you need to get the chip reprogrammed to match the engine and injectors. Either way, SOMETHING will be different than what the stock 305 ECM/chip is expecting. It's just better, in my experience, for it to be JUST the fact you have a bigger engine under that intake, not a bigger engine AND mismatched injectors.

aklim

If you don't get it reprogrammed to match, the ECM will think it has 19 pph injectors and will keep the pulse width within a certain limit. That will enrich your motor to the point it would waste gas and possibly be way too rich and wash out the cylinder walls

redlined4816

thanks for the info, does anyone know where i could get my chip reprogrammed and how much that goes for, or somewhere just to buy a new chip

aklim

www.fasterproms.com will do a truely custom job. About $350 for the first time and subsequent burns will cost $150, IIRC.

raul.garcia

The LT1 24lb'ers will work with the stock MAF 350 EPROM because it can handle a ±10% change, your 350 may be happy with 24s, if not invest in an adjustable fuel pressure regulator to make the 24s flow less until you can get the chip updated, your going to need one anyway, but that's just MO.

I run 30s in my 388 with a Holley AFPR.

87DJP2001

When I put my 350 in using the TPI intake from the 305 I changed the FI to 22# and got a new chip for a 350 from Fastchip. Remenber bigger injectors are not always better. They can be used except the additional programing of more expensive chip with little return in performance. Note: you will also require a new Knock Sensor for the 350 swap.

redlined4816

Well i already swapped the motor and the knock sensor was changed, and i just got the car running the other day. I have a computer for a 350 TPI that i was probably going to put in so with what you were talking about with that 10% change it can ahandle, so the lt1 24# injectors could possibly work fine with the 350 tpi computer? well at least i get my chip upgraded?

87DJP2001

The ECM for the 305/350 is the same and only the Chips changes. At this time I would install a adjustable fuel pressure regulator, the reason is you might(??) run rich with the 24 # FI. A suggested setting would be about 45PSI and it should idle at around 38/40 PSI. Something to think about. Been there and done it....

Unix

just another question concerning this topic.... DOES ANYONE KNOW WHAT SIZE INJECTORS THE 2.8 L MPFI V6 ENGINE HAD?

i tried putting injectors from the 305 TPI in my V6, lol it kept flooding the engine .

aklim

The thing I don't like about using an AFPR instead of a EPROM change is that the AFPR will dump more fuel or less fuel depending on your setting throughout the rpm range. Maybe you need more fuel at low end or high end or middle end but you will run rich all the way if you set it rich. EPROM changes are more precise.

This is just like advancing the timing by say 6 degrees because it makes it idle better down low. Now your WOT is also 6 degrees whether it needs it or not.