VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 High fuel consumption

Hello,

Our Chevy (Truck 1927, old post here https://vccachat.org/ubbthreads.php/topics/303130/1) has a very high fuel comsumption. I estimate (speedtachometer not working) about 30 liters for 50-60 kilomter = about 50L/100 KM !
- in the garage, the wall on the exhaust side is very black...
- sometimes you hear an explosion in the exhaust when turning off

We have the original manifold but with the electrical pump + filter.

- How can I reduce the "richness" of on the manifold ?
- did someone have the same problem ?
- is there another manifold compatible ? the guy who repaired the truck told me that the original one is not very powerful...

Thanks for your help
Gerard

Hi Gerard,

One thing came to mind when I saw the last photo of your engine (driver's side). You have an air filter with a metal elbow going into the carb. This setup is not original and might be a problem.

Even though you have a 1928 head on a 1927 block, the original setup for both years was to have a heat manifold on the exhaust pipe and have a metal, flexible hose bring hot air to the carb. An air filter is mounted on the intake side of the heat manifold.

The hot air setup atomizes the gas much better than the cold air which is going into your engine now. These missing components might be part of the lousy gas mileage that you are experiencing.

You can find information about the heated-air intake system in the shop manual. Copies are available from the Filling Station and others.

Here are a couple of pictures of the engine compartment of my 1928 Chevy truck. In them, you can see the heated intake air parts.

Hope this helps.

Cheers, Dean

Hi Gerard,
is it possible the vacuum tank is letting fuel get into the inlet manifold, via the vacuum line? If the vacuum tank overfills, that is where it goes. How is the electric pump plumbed in? If the pump is feeding direct into the vacuum tank, it might be as I've said.

To test, remove the vacuum line at the manifold, block the manifold fitting and turn the pump on. Beware, if it is leaking fuel, will spill form the pipe (pump is proven to be overfilling vacuum tank). If that test seems OK, start the engine and check again. A leak now might point to a faulty valve in the tank.

Why was an electric pump fitted? Vacuum tanks are far more reliable than electric pumps in my opinion and I would be changing it back to standard.

Regards
Al

It's a miracle the vehicle moves if it uses that much fuel. The plugs will foul. If the fuel is sucked down the vacuum line it will miss badly and the world behind will be a black cloud.50L per 100km; should be about 15. If it's that bad it's either leaking or the carburettor is way out of specs.