The Stovebolt Site Forums The Shop Area Engine Shop Engine Surging, won't stay running

'51 216

Since I changed the distributor I have been able to drive the truck. I forgot to tighten the intake manifold and ended up sucking in part of that gasket.

Since replacing the gasket and the metal rings on the intake manifold I cannot get this truck to run. It starts just fine, idles high with the choke on and then begins to surge.

It will start and rev up with the choke on like a normal engine would do. And then it starts to die and then it picks back up it just goes back and forth surging the RPMs.

I have double checked the timing and I can't seem to find a vacuum leak anywhere on the manifold or the vacuum advance. What am I missing where would you guys look next?

It sure sounds like a big vacuum leak. Are the rings holding the manifold away from the head?

Don,

I sprayed some starter fluid around the manifold to see if it settled and it made no change. The gasket is solid. I believe it is sealed...

Any harm if I remove the rings from the intake to test the seal?

You can tell if the alignment rings contributed to your problem once you remove the manifold. They will either be deformed, or you won't be able to bottom them out in the block or the manifold (due to debris).
A better way to check for a vacuum leak is with an UNLIT propane torch. Turn on the gas a bit and move it around and listen for an increase in RPM. To get a feel for what you are listening for, move the torch near the carburetor so the propane goes in and increases the RPM.
Carl

THAT is one heck of a good tip Carl. That is out of the ballpark for sure. Here's why...

The mechanics like to say use starter fluid for that. Problem being, it eats the paint right off making a huge mess. Others have told me to use a piece of heater hose and put your ear to one end of it and listen for excessive noise. The engine is noisy enough already that it doesn't work very well.

This one should go in the books somewhere! Any downsides to doing that at all?

An experienced mechanic spraying starter fluid around the outside of painted surfaces and inviting flames and/or paint damage? Maybe they like to play "passing the shirt".

It's dangerous enough carefully spraying starter fluid into the throat of a carburetor - STAND CLEAR WHEN STARTING.

The unlit propane torch technique is time-honored, simple, safe, and effective.

Oh I get it! Everyone knew that but stupid me! But I don't care, it doesn't diminish that it's a great idea and needs to be in an article somewhere!

Thank you for the suggestion.

Does anyone know where the vacuum line for the wiper connects on a 1937 truck?

I can only take a shot in the dark Justin. Vacuum on most engines originate at the intake manifold. I would check there and see if there isn't a line going from the intake to the wiper motor.

I finally found all of the little leaks, and cleaned the fuel pump (should have hot tanked the tank...).

Thanks for the help.

Clyde is running very nicely now. Going to install a fuel filter tonight and see if I can take him for a drive and return home under his own power.