C1 Runaway engine

[Michael Jones]

Last week, while doing some minor mechanical work on my 283, I removed and reinstalled the intake manifold and twin four barrel carbs.

The car started up without trouble and I went for a test ride. I had been out about a half hour and was in moderate stop and go traffic and some highway driving. Then I stopped at a light and took off running up through the gears. When I shifted from second to third, the engine suddenly opened wide open, near red-lining before I instinctively killed the ignition.

Siince I had just worked in the carburetor area, I immediately suspected a broken or unhooked throttle spring. I was surprised when I checked and found everything in place. I proceeded home without incident. My brother accused me creating one of those runaway car episodes!

I took the car out today and the same thing reocurred! Again, no telltale evidence. Any ideas? Next stop: my Corvette mechanic - this is downright dangerous!

Mike

[David D.]

Re: C1 Runaway engine

Mike, Check your motor mounts and bolts, on the frame and engine mounting points. Dave

[Ed Jennings]

Re: C1 Runaway engine

Mike, Your problem is probably somewhere in your linkage, but just as food for thought: Many years back I had a 65 with a 327/350 that ran away a couple of times. Turned out to be the accelerator pedal hanging up on the carpet at the right top corner of the pedal. It would only do it when I floored it. As you say, it was quite an experience. Mine happened 30 years ago, and I still remember it vividly.

[andy#34338]

Re: C1 Runaway engine

Michael,

An intake manifold leak could cause what you describe. Also check any vac lines you may have for cracks. This sounds like you need to take care of it right away.

[Gary Bishop]

Re: C1 Runaway engine

I also had the peddle hang up. Mine was the floor mat.

[Richard W.]

Re: C1 Runaway engine

I had that problem last year. Turned out to be a weak accelerator spring.

[Larry Allen]

Re: C1 Runaway engine

I agree with Dave, when you go WOT and have broken motor mounts the engine can twist just enough to lock the linkage. This was a common problem with Chevy engines of all years. The mounts don't look bad, under a load they will seperate. Prior to the new type of mounts with safety tabs, the engine would actually lift up and put the fan into the shrould as it locked the trottle.

[David D.]

Re: C1 Runaway engine

Larry, The only difference is that the C1's have the saddle type mount bolted to the front of the engine block, instead of side mounts. But, they can still make the throttle stick if the rubber at the frame mounting (driver side, usually) are deteriorated enough or if the bolts loosen up or are broken. I've seen them before with the head of the bolt still in place and looking like it is fine, until you look at the bottom of the mount and don't see a nut. The bolt snaps right where the threads start, off the main shank of the bolt. Dave

[Dave Suesz]

I had a similar problem with a 3x2V...

And it turned out to be a sticky throttle shaft on the rear carb. After polishing the shaft and shaft bore, it worked perfectly.

[John H.]

Most Likely Linkage Problem...

If you'll look at your linkage, you'll see that the actuating rod to the secondary (front) carb goes through a "U"-shaped pivoting bracket on the carb lever with holes for the rod in both ears; if the surface of the rod where it passes through the ears or the holes in the two ears aren't nice and smooth and free of burrs or corrosion, or the two ears aren't exactly parallel to each other and perpendicular to the rod passing through them, the linkage will stick in the wide-open position, resulting in "thrills" galore . Suggest you clean/steel wool the rod, verify the freedom of movement of the rod through the holes in the "ears" and that it will return from WOT, shim the pivot pin on the "U"-bracket where it goes through the carb lever so it doesn't "wobble", and lightly lubricate the forward end of the rod with Lubriplate.

[Michael Jones]

Thx - Ik'll report results

Thanks, guys. There wseem to be several prime candidates for the problem: linkagw, motor mounts, or vacuum leaks. As soon as I track it down I'll report the problem. Since I'm leaving town for about 3 weeks it may be awhile. I'll probably have to start a new thread.

Mike