Hello,

Stock 305 TPI, distributor had a complete meltdown and was completely replaced.

After it was replaced, my engine lost a noticeable amount of low end torque. It now bogs down when depressing the throttle.

Also, the mechanic said he had trouble getting it timed and had to paint a new top-dead-center line on the balancer. He did this by taking out the first spark plug to verify it was at TDC.

Another factor, the mechanic hooked up the computer and said it wasn't reading the RPM's

Any help you guys can provide would be great!

 

If your "mechanic" had to paint a new mark on the balancer, after verifying TDC on #1, chances are the Harmonic Balancer has rotated (rubber) and is shot. He should of checked that while he was there.

How is the Timing Chain in it? It could be bad/jumped a tooth.

 

Well, the mechanic mentioned the rubber and suggested that may have been the cause. However, the engine has approx 10,000 miles on it as it was replaced with a re-manufactured 305 at 67,000 miles. The car currently has 76,000. EVERYTHING thoroughly documented with receipts and signatures.

When the bad distributor died, it had a catastrophic failure. Could this have damaged the timing chain or the cam?

Also, the MSD coil that was in the bad dist failed as well. Could this have damaged the computer causing it to not read the RPM's?

Thanks

 

Not really sure what a catastrophic distributor failure is...

How familiar is this guy with these cars? Does he know the timing mark is straight down underneath the water pump instead of off to the side? He should but... These cars are weird, halfway between old school and modern.

Did he replace it with the correct distributor?

I'd bet it's just timed wrong, but that doesnt explain why the ECM doesnt see an RPM signal. That can cause problems too.

 

Basically the distributor shaft that's connected to the cam snapped and chewed up rotor, ICM, and the cap.

The Mechanic works at a GM performance shop here in Vegas that works primarily on classic corvettes and GM pony cars. He really seems to know his stuff.. although not the most detailed oriented individual.

what kind of problems can arise from the ECM not reading RPM's?

Thanks

 

Do you have a timing light? Do you know how to set timing? I would verify it. He may not know how to disconnect the ESC or EST (I forget what it's called) plug that disconnects the computer and allows you to set base timing without computer interference.

 

Update:

Hooked up my timing light to verify. The balancer TDC line was nowhere in sight, as the mechanic said. The new painted-on TDC line was at 6 degrees so I moved it to 7.5 and it runs MUCH better. I think I might try and advance another .5 degrees and see if that gives me even better performance.

If the timing was to retarded, do you think any engine damage could've occurred? I ran it for about 50 miles when it was running rough...

Also, I inspected the balancer and it looks new!? (as it should, engine has 10,000 miles) what would have caused the TDC line to move on the balancer?

Thanks for your help!

 

F the mark. Set the timing to where it runs the best.

No. Nothing to worry about there.

The outer ring sliding around on the layer of spooge that loosely associates it with the inner part.

 

Update:

After setting the timing to 8* it is running excellent.

Thanks for your help everyone!

 

Did you set timing with with the computer disconnected? The EST plug is what needs to be removed AFTER the car is running. This unplugs teh computer from the distributor giving you a way to read BASE timing. The computer does all of its timing on the fly assuming the base timing is correct. If you set base timing with the computer connected you will make it run AWFUl because you will just keep moving it way out, and the computer iwll keep adjusting it back. You MUST disconnect it to set base timing properly. Do a search, you'll find it. It's usually a brown wire near the A/C stuff with a relatively easily accessible plug. After you get base timing right, tighten teh dizzy down, turn the car off, plug it back up, then disconnect the battery to clear the code that was thrown by disconnecting the spark control for a minute and then reconnect and it should be fine.

Factory is 6 degrees advanced.

 

What InfernalVortex said, 100%.

6* base timing with the EST disconnected becomes about 24* at idle when the ECM is commanding the timing. Trying to set the base timing without the EST wire disconnected (per factory timing procedures) is an exercise in frustration.

 

Thanks guys. I know to set the base timing with the EST unplugged, but I've Ive always unplugged the EST BEFORE starting the car. Will it make any difference in unplugging AFTER you start, then setting the base timing?

 

I don't think so, but I've always done it by unplugging before a start. The thought of yanking connections apart that have unknown voltage flowing through them, connected to solid-state electronics on either end.... I just don't. It's probably just fine, but why take a chance?

 

I never had an issue with it. Im PRETTY sure that's the procedure my service manual indicated... but it's been years and years and years since I had a factory EFI setup in my car, so I wouldnt be surprised if I'm remembering that part wrong.