Greetings everyone.

I recently installed a small block 350ci motor with 882 heads in my 1985 Camaro Berlinetta. The original motor for the car was a 305ci LG4 with a computer controlled quadrajet carburetor. I used all of the original components from the old engine on the new engine (carb, intake, accessories, etc) and was told that my carb should handle a 350 just fine. I have the engine timed and there are no vacuum leaks. When I attempt to start the engine, it will fire up for about 3-5 seconds, backfire, and stall out. I have trouble keeping the engine running even if I step on the gas. Could it be that I have to re-jet my carburetor to accommodate the additional displacement?

I'm going to have to keep the q-jet on the car if I want to keep my digital dash, (so I'm told) so if the carburetor is the culprit of this maddening problem, I don't think the solution will be as easy as just throwing a Holley on it.

Thank you for any help and advice any of you may have for me.

 

I've been at it all day with the thing. It definitely seems like the engine is starving for something. I pulled one of the plugs to see if there was a white residue or if they were fouling out, but they look fine. If I step on the gas, I can keep the engine going, but that's after 3500 RPM, and at that, it still wants to stall. These symptoms seem to point to something like a vacuum leak from hell, but there are no open holes on the carb or intake. The fuel pump, filter, and line were recently replaced, and there are no leaks from the pump to the carb.

What gives?

 

Check the distributor and cam alignment.

 

The distributor sits flush with the intake and correctly meets with the oil pump. When timed so the engine will start, the distributor is in the same position as it was when I drove the car a couple of years ago. I'm 100% certain that the distributor is installed correctly, and even though I did not use a timing light, the ignition timing is *close* enough to start the car. I played around with the timing a bit to see if it had any effect on the problem, which is does not.

I'm going to troubleshoot a little bit when I get back home. I'll have my brother sit in the car and crank the motor over while I shoot some starting fluid down the carburetor. If I can keep the motor at idle, then I suppose I've isolated a fuel system issue. I'm open to suggestions, gentlemen.

Thanks in advance.

 

So I sprayed a bunch of starting fluid down the carb while my brother cranked the motor over. The motor idled so long as I was spraying the fluid, then stalled out and died when I stopped. As far as I'm concerned, this isolates the problem as a fuel delivery issue.

 

are you using the same fuel that was in it two years ago?

 

Did you use the 305 damper on the 350? If so, you may have a mismatch between the timing mark and the timing tab. The 305 timing tab was at 12 o'clock, while many older timing tabs were at ~1:30.

If this is what you have, your timing will be way off.

 

I'm using the 350 damper.


As for the fuel, I recently gave the car about 3-4 gallons of fresh gasoline out of a gas can.

What I've discovered so far is that the engine is actually in decent health, but the trans is apparently on its way out. When the engine was at idle, I discovered a pretty steady leak coming out of the front seal at the torque converter, which shouldn't be happening because I replaced the seal prior to the engine drop. When I observe the torque converter at idle, it appears to "wobble" 1/4 inch in and out of the trans, which is something I've never seen before. I wanted to establish that it was actually the converter that was wobbling, so I unbolted it from the flexplate and started the car and confirmed my suspicion. When the converter was free of the flexplate, I tried to freespin it only to find that after every 300 degrees or so, it would become INSANELY difficult to rotate, and even though I'm no expert, I suspect that is why the engine has difficulty at idle. I was pretty sure the converter was seated correctly, but it also seems like there's a little less clearance in between to converter and flexplate than there should be.

I'm going to put the trans from my 89 IROC in the car to see if that makes any difference, because at this point, I feel that running the engine with the current trans will damage the thrust bearing.

 

Run it with thr trans unbolted