My car seems to be getting only around 10mpg. With the old 305TPI (LB9) it was getting 18mpg and 25mpg on the freeway. The only thing i have done is put in a 350 TPI (has old 305 TPI set up on it) with 21lb fuel injectors, and a mild cam. The guy who put in my engine says that it has around 275hp at the wheels. There shouldn't be that much of a difference in mileage should there? Will this pass as time goes on? I do know that the cat and muffler are bad and am getting those fixed next week. What should i do? Any help would be great! Thanks!

 

Something has got to be wrong. What kind of chip are you using?

 

What do u mean? I didn't get a different chip.

 

do the cat and muffler first then worry about it

 

you should be using a 350 chip, not a 305 one

 

oh also, what knock sensor are you using? a 305 one is more sensitive than 350 so your ecm might be over retarding your timing due to false knock

 

Ukraine Train:


Where can i get a 350 chip, what kind do i need (brand/name) and how much would it cost? Thanks!

 

since your car is an '86 i'm assuming it has a mass air setup (MAF sensor). the easiest way to get one is find a used ECM with a chip already in it that came from a 350 with Mass Air tpi, not speed density tpi. the Speed Density tpi computer number ends with 7730, that's not the one you want, do a search for 'MAF tpi computer number', i dont know the number off hand. there's always some floating around ebay for $50-60. speed density was used 90-92 i believe.

 

ok thanks ill check it out!