i just did the l03 to lo5 swap and now my car is slow as hell. actually its slower then the l03. but right now i have the hooker headers with the 3 inch y pipe and then i put a flowmaster where the cat goes. is my car slow because i dont have a full exhaust or could it be another problem? i thought v8's didnt need any backpressure?

 

ok just checked the battery terminals they are ok. i also checked to see if the wires were crossed and they are also ok, unless the wire pattern for the lo3 and lo5 are dif. i changed everything that was recommended for the 305 to 350 swap except the chip. i kno i need to change the chip, i had bought a hypertec chip for the 350 caprice but when i installed it my engine light came on so i just went back to the 305 chip. so is it just the chip thats causing the problem? it feels like i got like 90 horses!

 

Wow you are barking way up the wroing tree with this backpressure business. It's horseshit.

Your problem is most likely a tuning issue. It's not getting fuel and spark at the right times/amounts. Even if you use the chip out of a truck for instance, it's tuned for a vehicle as heavy as a truck. It will be all wrong in your car. A 305 tune will do that too. It will be terribly inefficient at making power and get terrible gas mileage to boot.

I dont know as much about this stuff as I'd like to, but Im going to say that it could be running lean because the computer is pumping enough fuel for 305 cubic inches, and your motor is inhaling enough air for a 350. So you've got more air than fuel. Under load (say wide open throttle acceleration) this running lean will cause knock/detonation and the computer will retard timing as far as it needs to.

Having the spark advance pulled out like that is a big deal and will hurt performance. I've heard people say more than once that when you're building a motor, the extra power you get from going to a higher compression ratio is far less than the power you lose after you have to pull timing out to keep it from knocking. Basically, it's better ot have a more tolerable compression ratio and add spark than to have a higher compression ratio and not have enough octane to support the ideal spark timing range for the motor.

But yeah, with the 305 chip, nearly every single setting will just be wrong and it will run like crap.

Your options as I see them:

1. Learn to tune your own chips - maybe look into the EBL

2. Swap over to a carb setup.