I have a 91 Firebird formula that I got last November. It originally had a 305 tbi engine but that was gone and the guy I bought it off of had a 350 tpi and 700r4 setup waiting to be installed out of his 88 formula. He lost interest and I acquired it at this point to get it running and sell it. Now being the type of guy that I am I can't leave well enough alone, I freshened up the engine with a .030 bore and new speed pro hyp. pistons, timing chain set and gaskets, stock cam and heads, and hooker long tube headers. I got a wiring harness and computer out of a 91 trans am GTA and a custom prom. All of the engine sensors are from the 88 except the map sensor. I replaced the fuel pump with a tpi unit and have 42 psi, got the engine running. Now I noticed that after 1/4 throttle it pings severely, like a ball bearing or 2 in a glass beer bottle rattling around very fast. I tried backing the dist timing down but that did not help other than losing more power, I then tried backing timing down via the chip and no difference in pinging. I also tried 110 octane race fuel and still no difference. I checked the balancer to make sure that it didn't slip and it is correct, (at least to a new gm balancer). I also triple checked the dist to make sure that it wasn't a tooth off and it is fine. The only thing left that I could think of was cam timing and as of tonight it is right on straight up. I am running out of options and I have a built engine on a stand for my 91 Camaro vert that I am now thinking of throwing that in it to get it the heck out of here. I have built 350's in the past and had no problems till this one. Is there ANYTHING that you guys can think of that I might have missed??????

 

Aaron

I would check fuel pressure while approaching 1/4 throttle area - if you are loosing FP engine might be going very lean. Along the same line I would get ALDL going from idle to suspect areas. If engine is leaning out - BLM will climb (in value) and this will be visible in a data log. Also check KS map - this will tell you if its true knock or something internal.

//RF

 

Well I did datalog a couple of tirnes but I didn't notice anything unusal but Thanks!! I will try that once I get it back together.

 

Got the car back together, fuel pressure is at 40 psi at idle and 45-47 psi when vacuum source is unplugged and I noticed when I here the pinging I see a cloud of smoke out of the tail pipes, but as of right now I can't tell what color it is. Any other ideas that this could be??? I also was wondering the differences in the computer chips, because the one I have is out of a 91 305 tpi although I reprogrammed it using the aujp bin. The spark control module remains the same however.

 

check your timing, my motor use to ping becuase I had my timing advanced too much