This has probably been reviewed before, but I am fairly new to this board and have a few questions. I am running a tpi 350, .30 over, comp cam, and 76cc heads... I had the 305 to begin with. My machine guy told me that some guys say they can use the oem 305 injectors and crank the preasure up high enough and actually get better atomization with the smaller injecter and higher fuel preasure vs using a oem 350 injector or bigger. I am curious to the opinion of others on this matter.

 

this is somewhat true, smaller injectors with higher pressure do cause better atomization, the 305 injectors are 19# and the 350 injectors are 22#, theirs also something about using the 305 ecm with your 350 and i forget what that does though hehe.

 

Couple issues you may get doing that.
1. Your chip is still from a 305, so the ecm thinks its still runnin a tune for a smaller motor. This can cause lean problems at the top end.
2. Uping the pressure is good to a point. If it gets too high, you may over-power the injectors to where they cannot close.
Whats all this mean?
you need a chip to be burned to allow the ecm to operate a mild 350. Other issues you may or may not see is with the larger fuel demand the motor needs may be more than what a 19# injector can provide. After tuning it to not run lean the ecm may also hold the pulse for too long, beyond the dudy cycle it should see.
My advice, get some 22-24# injectors, and a custon chip. Whike you may run rich on a stock chip, it is better than burning a piston in a lean situation. Plus a larer injector leaves room for more modifications, should you be so bold.