Thread: runaway 350

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hello, I have a 59 Chevy PU with a goodwrench 350 in it. It was set up for high stall torque and turbo 400 transmission when I bought it. It was running great until a few days ago. At the stop light when I left it in gear and the brake on the rpms would surge so high I had to shove it into neutral and then back in gear when green light. It was a pain but manageable until today.
It surged and I smoked the tires coming off a stop sign but the engine didn't back off and kept on surging! I put it in neutral and backed off the gas but it stayed at wide open throttle, so I turned it off.
The linkage was not stuck.
I got a ride home and got another carb that was working on another engine when I took it off and replaced that onto the current problem only to be surprised it did the exact same surging of wide open throttle.
I had it towed home and figured it was a major air leak and maybe my intake manifold gaskets had failed. So we replaced those and new carb gasket and checked and rechecked all vacuum lines and started it up and it still surges to WOT on start up!
I looked in the carb. and the floats work and the lower valves are closed when the throttle linkage is at idle.
What is going on here? This is crazy.
Has my fuel pump gone bizerk?
Has someone put nitro into my tank?
Thanks for any suggestions.
Ringo

Are the secondary throttle plates hanging up on the gasket under the carb? What carb have you got on it?

I have tried 2 carbs. The first one is Edelbrock the second one was a Holley.
The Holley was working fine when I took it off another engine a few weeks ago but it didn't solve this problem. I put the Edelbrock back on and no the secondaries are not hanging up on the gasket.

This morning I am thinking of replacing the fuel pump. That is just a guess that maybe it is creating too much pressure. I have never heard of that before but now we are just guessing and eliminating all possibilities.

My second guess is that the timing slipped and it is way out of time now.

My third guess is that both carbs went bad at the same time.

My fourth guess is that it is haunted.

I haven't had a lot of experience and appreciate your response.
Thanks

Check for broken or loose motor mount. If it's broken or separated the engine will lift from the torque and pull the throttle linkage causing rapid and unexpected acceleration.

It can't be the fuel pump or the timing. It has to be getting airflow somewhere, and gas to go with it. The broken motor mount idea is a possibility but it should fall back into place when the torque reaction goes away, like in Neutral.

Originally Posted by fitzwilly

Check for broken or loose motor mount. If it's broken or separated the engine will lift from the torque and pull the throttle linkage causing rapid and unexpected acceleration.

That was my first thought too...........

does the gas smell ok?

Broken loose motor mounts!
Engine and transmission moved forward about an inch making the linkage too short!

Thanks for the suggestions very much.

Now all I have to do is fix it.