VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 first and second gear hesitation

Sometimes when I drive my 1954 Bel air 3 speed I experience a hesitation / sputter.

It only happens in first and second gear, and when I accelerate quickly.
When I shift into third it goes away.
When I drive through first and second SLOWLY it doesn't happen.

It runs great at highway speeds with no hesitation. All ignition components are new, except the distributor. The car has electronic ignition.

This has just developed and nothing was replaced or changed out before it happened.

The fuel filter under the car near the tank is new. The other fuel filter before the carb is clear and it seems to be getting plenty of gas.

I thought it may be a tired fuel pump but it runs fantastic at 65 mph with no sputtering or hesitation.

Does this sound like ignition or fuel?
Carb? or Distributor rebuild?

Is the accelerator pump working correctly?

Great idea. It could be the issue. If I floor the gas in park it also hesitates. I will have to figure out how to check that out. Thanks.

It’s pretty simple. Run the engine a few minutes to make sure the carburetor float bowl is full.

Turn the engine off and remove the air cleaner. Look down the throttle bore while you manually open the throttle.

You should see a small stream of gasoline shot down into the throttle bore.

OK, My carb shoots out plenty of gas into the throttle bore when I do that. I can not identify or see a small stream of gas, but it is filling up with gas.

It appears that the accelerator pump is working. Maybe even too much.

I am not sure if there is stroke adjustment on the carburetor you are using.

The other item to re-check is the timing. On my car there is enough wear in things that the timing I set statically is not the timing when it is running.

I apologize if I missed this other point in a prior post. Is the heat riser valve operating correctly?

Thanks, the valve in the riser turns very freely about 60 degrees or so. There is a rod that sticks out of the riser that I can turn to engage the valve but it is not connected to anything....should it be?

Fixed!

I checked the timing and the BB was a little before the fixed marker, not dead on. The car runs beautifully with no pinging so I didn't touch the timing.

The accelerator pump is working and the fuel filters are new.

The original oil bath air cleaner was taken off the car by a previous owner and it now has a 4" round chrome air filter on it. I don't think that air filter is the best choice for the car..... the gasses coming out of the vented valve cover seem to foul the paper air filter quickly.. I changed that filter out with a new one and now no hesitation at all.

I am going to try and find an original air cleaner because i have a feeling I am going to be changing the 4" round aftermarket ones too frequently.

Glad that you found the source of the hesitation

I wonder if the down draft tube on the engine is partially blocked. I agree that you will get some blow-by out the valve cover vents when the car is sitting. Most of those gases will be pulled out the downdraft tube when the car is moving.

If the rings are worn badly there will be a lot more blow-by. Have you checked the compression?

I haven't checked compression but that is on my list. How do you clean the down draft tube? Does it unscrew somehow?
It does look pretty dirty with caked up grime.

The tube is an interference fit into the hole in the block.

On most Chevy 6’s there is support strap welded to the tube that is attached to the side of the block. That is a little awkward to get to but fairly easy to remove the mounting screw.

Getting the draft tube out of the block can be challenging. If you are lucky you might be able to pull it up from the block.

On my car I had to use a piece of wood about 1 foot long and hammer to drive it out from beneath the car.

I have seen similar issues with air flow restriction with the various elements that fit the very common aftermarket 4” round air cleaners. My neighbor has a ”˜57 Oldsmobile with 3 2 barrels on it. We were having idle and hesitation issues similar to what you described. One day he happened to reinstall the air cleaners in different positions. The problem immediately went away. We swapped them around and made the problem happen again.

We determined that there were different filter elements in the various air cleaners. He ordered new air filter elements like the one that worked and has not had any problems.

I would not be as ready to blame contamination from the blow-by gases.

I removed the tube and cleaned it out with Kerosene and then brake parts cleaner. It was dirty but not as bad as I thought it would be.

My filter was dirty but not clogged. I don't know how long it was on the car. My thought was the gases coming out of the vented valve cover may have prematurely fouled the filter.

Anyway, I am not having the hesitation problems with my new filter and wouldn't be surprised if the element is the difference.

In 1954 the standard oil-soaked mesh and the optional oil bath air cleaners had minimal restriction to air flow. On the other hand they were not near as effective at filtration as the filter elements we use today.

Yes, the filter elements are easier to change and less messy to deal with for sure.

Hesitation due to carburetor air flow restriction should be added to each troubleshooting engine performance list. I will try to remember it and add to my mental list in the future. If enough of us do that it might be something we consider next time we have to try and diagnose a problem.

Absolutely. Start with the easiest check first........... a solution to an issue isn't always the most complicated!

I just pulled my plugs and checked the compression. The plugs have 600 miles on them and are bone dry with hardly any soot. More of a very light tan color.

These are my compression #'s
The engine was cold and dry.

#1-100
#2-100
#3-100
#4-100
#5-100
#6-105

Do those numbers look ok? Or are they too low? The car runs fine with plenty of power but I don't push it.

Those are very good results in 2 respects.

They are plenty high and they are very uniform. With 7.5 to 1 compression ratio the theoretical is 110.

Did you do a “wet” compression check?

Have you measured the vacuum at idle?

I haven't measured the vacuum yet and have only checked the compression dry without even driving the car first.

Is it true that the numbers would be higher if the cylinders were we.....t like if you were to squirt oil down into the spark plug holes?

Yes, wet will be higher.

In your case I do not expect large increases. There will be some, maybe 10 - 20 psi. The oil makes the rings, especially the upper ones, seal a little better.

In most cases a wet test will help determine if low compression is due to ring & cylinder wear or leaky valves.

An engine at operating temperature will also give you higher results due to smaller clearances from heat expansion, but as Rusty says above, your numbers are good and consistent.

That is good to hear. Thanks.