Alright, I'm new to this message board but not to F-bodies. I recently rebuilt the engine in my '89 Trans-Am as it had a spun front main bearing. Upon pulling it, I found it was a 305 TPI. Since the main was spun, I decided to get a 350 4 bolt block, but I reused my 305 heads as they were H.O. heads and wanted to save a little money...plus it raised the compression to semi-compensate. Besides, this is going to be a daily driver...sort of. Anyway, It originally had a 350 according to the VIN. In doing this swap back over, I have reprogrammed the PROM for the 19lb. injectors from the 305, installed a 350 knock sensor, 350 ESC module, timed the ignition to stock specs, eliminated the cold start that was on this intake set-up from the 305, eliminated the EGR (on the PROM as well), bored the block out .030 over but used dished pistons to keep the compression reasonable, and installed a stock 350 spec. roller cam.

Now that the background is there, heres my question. What am I missing? I have had trouble getting her to fire up, cold or warmed up. It takes a long time of cranking and feathering the pedal and basically monkeying around with it just to get it to fire. Once it finally does start, it runs rough at first, barely runs really, until it warms up a little. After that, it seems rough still and a little hesitant in the throttle response area. Im running premium gasoline to avoid knock and ping by the way. Is it possible that I have to adjust the timing away from the stock 6 degrees? Should I retard it to like 4? 2? I'm at a loss here. I have replaced all the supposedly 305 only components and the only thing left is timing...or so it seems. Anyone have any other ideas? Since this is sort of a mutt motor now with the various 305/350 mixed components I need any advice to get her road worthy to drive daily if I want...not that I would. Honestly, I just want to be able to turn the key and have it pop right off, not crank her for 10 minutes first. Anyway, any help would be greatly appreciated.

Sorry about the novel here, just wanted to get the whole story out there to limit the possible causes. Thanks.

 

creepingdeath? are you in ontario? or is this a new creepingdeath?

305 and 350 parts mixed like that should be just fine, sounds like the motor was a solid build. (not so sure about a non-perf roller cam used though, why?) this is a 4 bolt 1pc RMS roller block? just making sure...

If I had to guess i'd say it was the computer setup. Usually people shy away from it since it's complicated, but you seem to have a handle on it. Have you ruled it out?

 

What's your fuel pressure?

 

I am a new creepingdeath...lol...Im in Florida.

Fuel pressure is within specs for stock though I have been told i may need to up the fuel pressure from the stock regulator...either aftermarket or tweak the stock one. However, it should be ok for the setup I have as Its not a race motor or anything and aside from the compression and bored cylinders, its mostly stock.

And yes, it is the stock 4 bolt 350 roller cam block, one piece seal...i didnt go to a performance cam as the stock 350 with my setup seemed like it would make plenty of power and still give me the vacuum i needed to run my auto trans. and a/c. Didnt want to get too crazy with the radical cam hehe. The computer I checked and they should be the same (have the same part number in that year for both 305 and 350). The next step logically to me was the PROM, which unless it wasnt programmed properly should be ok now too. It doesnt run any differently than before I sent it out so I doubt that is the problem...though I will be checking it on a scan tool when i finally do get it over to my mechanic. So in your opinions thus far, timing shouldnt be an issue here then right? I know the computer adjusts it but is that adjustment based on the base setting enought that if its off or if it needs to be 4 degrees and its 6 on my application that it would run like this?

Basically, if nothing obvious is popping into mind that I missed or forgot, I need to get a scan tool on it at my mechanic I guess. I appreciate the responses though. Im so close its driving me nuts that I cant just drive her...but Id rather have her right before i start putting miles on her. Thanks again and if anything else comes to mind keep posting. I will definitely be checking everything over again.

 

If it was me I would hook up a vacuum gage and when it is finally running the best it does, see where your at. I also would try having someone turn the distributor when you try to start the car and see if that helps. I would hazard a guess that the timing is retarded too much. Also have you ruled out a vacuum leak?

 

Almost all the main vacuum lines were replaced with the motor rebuild, and I have sprayed the carb. cleaner/ equivalant around vacuum lines to see if it bumps rpm...so Im fairly confident its not a vacuum leak. However, I will be double checking them all anyway.

Can I just turn the distributor while cranking on this car? Would it work with all the computer control still hooked up trying to correct it or should I do that with the computer bypassed procedure? I know just enough about the computer to get in trouble :-p.

 

Yes, you can move the distributor while you crank it over. Even though the computer is controling the advance there is still a certain amount of mechanical advance already built in the distributor. If you turn it too far one way or the other, the car will either turn over slower or faster, possibly even pop thru the plenum which will then tell you, you moved it too far the wrong way. Give it a shot.

 

Still sounds like a fuel pressure problem to me. Have you verified what the pressure is when you're having these problems, or just had a gage on it once and saw it was okay then?

 

The fuel pressure checked ok while running, cranking, etc. Also, before I did the rebuild, the engine ran fine, fired right up everything was great...aside from the banging of the crank trying to throw itself out of the block. This is why I thought it wasn't fuel related, well mechanical pressure anyway...I guess it could still be in the computer control of the fuel to the injectors though (pulse). I will double check that as well just to be certain though.

I am also going to try and rotate the distributor a little and see what happens.

Again, I appreciate all the responses, I feel like Im narrowing it down.