91 z28 305 to 350
 

I have a 91 z28 that came with a 305. i put a 350 with 305 heads, cam, roller rockers, twin 58 throttle body, 24lb injectors, headers and 3" flowmaster exhaust. the car doesnt run right. when i give it full throttle it hesitates and wont get on it. what do i do. what could be wrong.

If your still running your 305 chip thats the problem it's written to run with 19 pound injectors not 24. Your going to need a new chip before it will run right or swap the injectors.

Re: 91 z28 305 to 350
 

I wouldn't put 19 pph in. You might go WOT sometime and lean it out. Switch the chip or get a custom EPROM at www.fasterproms.com and it should be fine.

What ratio of roller rocker and what cam? 305s never came with roller rockers and I believe the cam is different than the 350s. What have you done besides the twin 58 mm TB? A friend of mine tried it and went slower until he changed the plenum, runners and manifold.

test

Well I saw that he was using the 305 heads so hes proboly not making that much power. I dont know what kind of cam he has but if it's not a big one the 19 pph injectors will be fine till he gets his new chip burned.

Re:
 

It's been said that the knock sensor is different betwee the 305 and the 350 motors. I ran with both the stock 86 305 and aftermarket ADS superchip for a 86 305 both preformed w/o problems.
I have a comp cams 272hr and ported heads. No real problems except for alot of retard being pulled out at WOT off idle. I just put my own modified chip in it about 2 weeks ago and haven't monitired again to see if I'm still getting the knock, pulling timing out of the advance yet. If so I am going to desensitize the knock sensor with resistors vs. buying a new one.

Problems in order:

A.) You have 305 heads that flow like crap to begin with on a 350 block and they are probably not helping you especially with that new cam.
2.) You have 24#/hr injectors and a stock chip that thinks they are still 19#/hr. Conclusion, they are dumping a tremendous amout of fuel into your motor.
D.) Your Throttle Body isn't helping you. You should have a 48mm or 52mm TB sitting there not a 58. A 58mm TB is unnecessary until you get near 400hp or so.

We need to know your EXACT setup including cam specs, header Primary tube diameter, Ported/non-ported TPI or heads, etc.

Hi, I'm trying to do a similar swap from a 87 iroc 305 with 5 speed to a L98 from a 91 trans am with auto. Havn't completed it yet but i've done research on the subject. When going from the 305 to the 350 I found that your supposed to change 4 things, the distributer est module, the esc module the knock sensor and the chip. Along with the injectors. My problem is extended because 350s didnt come with 5 speed manual trans. So I'm trying to find out how to get a 350 chip that will work with manual trans. Any suggestions will be greatly appreciated.

The only way to get a 350 manual trans chip is to start with a 305 5-speed chip and have it custom made into a 350 manual trans chip. A Corvette chip will not work because those came with oil temp sensors, and you will get an SES light for the oil temp sensor not working. I already tried that one. A custom chip is your only solution.