VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 1928 engine surging

I am working on 1928 Chevrolet light truck for a friend. It had not been run for 3 to 4 years. It has the stock ’28 engine. I got it running and it will idle relatively smoothly. When I try to take it on the road, the vehicle surges very badly making it not drivable. I have cleaned the plugs, adjusted the points and adjusted the valves. I have tried a recently rebuilt (Chip Sweet) carburetor; 2 different modern coils with a “add on” condenser; changed spark plug wires. The engine has enough vacuum for the vacuum tank to pull gasoline from the tank to keep the vacuum tank filled.

Can anyone help me determine what might be causing the engine to surge when under load?

Dave you might want to see if you have the same vacuum reading at the fuel tank as you do at the manifold. If not, look for leaks in the fuel line and vacuum tank. If okay, I would suspect a rusted pick up tube in the fuel tank or a malfunctioning flapper valve in the vacuum tank. Do you have a fuel filter anywhere in the system?

Another thing to check is the vent opening in the gas cap. If this vent hole is plugged, a partial vacuum is created in the gas tank and the amount of gas coming out of the gas tank is reduced to a dribble.

Been there and done that.

Cheers, Dean

Reading your post I am thinking that nothing you have tried so far has made a difference. If that is the case I am thinking vacuum leak. Have you performed a compression test? Weak cylinder(s) can be a contributor.

Thanks for all the suggestions. I will look into those tommow evening or Monday. I talked to Verlyn Hessman since the initial post and he gave me some suggestions regarding timing.
It is great to have support out there when you need it.
Initially there was no tube between the heat stove and the carb. Putting one on improved my ability to have it idle.

Dave I had a problem about ten years ago with my '25 sedan. The hold down screw on my distributor condenser was loose and caused the spark to cut out for a moment and then cut back in before the engine quit. It acted like fuel starvation but was electrical. Usually electrical problems will give a sharp repetitive engine miss. It was like turning the ignition off and back on. It's worth a look and an easy fix. Good luck.

Yes I'd suggest a compression test can reveal a number of problems, is it running the 28 4 screw vacuum tank or the 8 scew one?, Ray

It is running a 4 screw vacuum tank. I will run a compression check when I get another couple of hands to help me.

My '28 was a bucking bronco recently. To find the problem, I went through the carb and vacuum tank. The story is here: 1928 fuel problems and my fixes.

Hope this helps. Dean

I would like to thank everyone for your suggested area to explore to get this 1928 light truck running and on the road again.

Yesterday I purchased a new 6 volt condenser to install on the "modern" coil. This morning I started the truck and it ran great. I took it down the road with no bucking! Only drove it a couple of miles with at top speed of about 30 mph. It ran great.

When I got the truck to work on, it did not have a heat tube from the exhaust to the carb and did not have a condenser on the "modern" coil. I also put on a good set of spark plug wires and reset the timing.

Hopefully the owner will drive this truck rather than letting it set!

Good news! Thanks for helping another great old Chevy to be roadworthy.

Cheers, Dean

Glad to see it was a simple condenser problem instead of a vacuum pump or fuel tank problem.