Q&A

Mailbag: Solving Ignition and Oil Pressure Issues on a Swapped Small Block Chevy Engine

 
hei distributor tune up

(Image/Hot Rod Network)

You’ve got questions, we’ve got answers. We work with the Summit Racing tech department to help you tackle your auto-related conundrums. In this week’s Mailbag, we’re troubleshooting ignition problems on an uncooperative small block Chevy swapped into a Monte Carlo.

Q: I own a 1984 Monte Carlo SS with a stock 350 out of a 1974 4×4 pickup truck. The engine has four-bolt mains, a Quadrajet carburetor, and an HEI ignition. The car has been a daily driver for the last three years.

I experienced a problem this past summer. The engine began to miss and “hang up” when I let off the gas. When I checked the engine over, I found the top of the distributor had locked up, right underneath the rotor. I switched distributors and the car ran fine for three months, and then the same thing happened. I also noticed the oil pressure had dropped to 20-25 pounds during idle.

Do I have a problem with the oil pump, the cam, or a blocked oil passage? Can I fix the engine without having to tear it down?

A: The problem is in the distributor.

We suspect one of two things. The more likely problem is that a buildup of varnish or gummy residue is causing the advance mechanism to stick to the distributor shaft. You can check this by turning the rotor and quickly releasing it. The rotor should snap back into position. If the rotor is hard to turn or won’t turn at all, the distributor needs to be rebuilt.

The other cause could be the advance weights sticking in the outer position, and the return springs not being strong enough to pull them back. Advance weights stuck out that far means the timing is advanced too far. This will cause the engine to have trouble idling, and the oil pressure will drop.

You can try and salvage the weights and springs by removing and reinstalling them. Better yet, buy a new set of weights, springs, and bushings and rebuild the top half of the distributor. Either way, make sure to put a small amount of white grease on the pads the weights slide on.

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