The Stovebolt Site Forums The Shop Area Engine Shop 1961 Chevrolet 235 K20

Hello Everyone!

I am having trouble with my Engine. Over a course of around 350 miles my Engine lost more and more of its power and it seems to be running on less cylinders and is sputtering. First the idle was fine and the problem was only in high revs, but now it’s all the time.

Before I left for the trip I readjusted the carburetor, a Rochester B, to what I thought was leaner. I turned the idle screw 180 degree inwards.

On the trip I noticed the power of was declining so I checked on the spark plugs wich I found white plated. I then tried to re-gap them to 0.035. I then ran the engine for about 15 miles, but it was running horrible. I then stopped again and cleaned the spark plugs with 600-type sanding paper and gapped them to 0.04. The engine was then running better but still bad, so I went with on with it for the last 150 miles of the trip. On the last 50 miles the engine was running extremely bad and only had some power in very high revs.

I ordered new spark plugs allready, but I hope I did not break more. I am at my mothers place so I don’t have Access to a vacuumeter

How can I make my old lady run well again? I appreciate all the help I can get!

I am native German so my english might sometimes be weird.

The white color of the spark plugs suggests that you probably have a vacuum leak somewhere. Air is getting into the engine without going through the carburetor, which is making the fuel to air mixture too lean. One possibility would be the carburetor being loose on the intake manifold. Another might be looseness between the intake manifold and the cylinder head, or a large vacuum line being disconnected. Try using a gas source such as a Propane or acetyline torch with the fuel gas flowing without being lit, and pass it around all the gasket surfaces, looking for a place where the engine speed increases or the engine begins to run smoother as the gas is drawn into the vacuum leak. Other possibilities might be very late ignition timing due to a the distributor adjustment getting loose, but that would not account for the condition of the spark plugs.
Jerry

Your English is just fine. Far better, I'd wager, than the German of most who frequent here.

White plugs sound like it was running too lean. I would start with new plugs and put the carburetor adjustment back where it was. Did the engine get warm on your trip? High engine temp can be a result of lean mixture.

Any chance the fuel pump is going or fuel line is partially blocked

Hey, and thanks allready for the feedback, I will check for leaks tomorrow, it is night here. The fuel pump and the Filter were replaced last year, but there is some crud in the filter, but the filter is a modern style one hooked up to the fuel line and it the paper looks fine and the gas tank came new some weeks ago. I believe the white spark plugs come from me setting the Rochester to lean. Does the mixture get richer or leaner when I screw it out? In German angle barrel BVFs it gets richer when you screw it out, so I screwed it in a bit hoping for improved mpg.

Check to see if the heat riser is stuck.

The mixture should get richer when you turn the screw out. Half a turn on a screw is quite a bit.

Can I ask about the heat riser point made by Gord&Fran? On my 46 the shaft was seized so I forced the flap to block off heat from getting to the bottom of the carb. I don’t see my 46 getting out much in the winter. Are you suggesting that if the flap is stuck open it would cause carb to run rich?

Hello, I just checked the heat riser and the thing is moving freely and the bi-metal-spring is gone. I suspect me running the engine lean burned out the spring wich caused the carb to overheat. I did not run it yet as I am waiting for my friend to be the emergency hauler.

If the weight is down to the left side if I look at it from the front, is it open or closed? It seems it was stuck in that position.

The heat riser allows exhaust heat to flow to the bottom of the intake manifold, increasing intake air temperature in the manifold, thereby increasing fuel vaporization and preventing fuel puddling below the carburetor. Blocking the heat riser closed can result in rough and difficult operation due to fuel not reaching the cylinder, especially in circumstances of low intake air velocity at low engine RPM.

If the heat riser valve was stuck open, exhaust heat will continue to heat the intake manifold, resulting in high intake air temperature, increasing the possibility of preignition or detonation.

I have a 216 intake and exhaust manifold assembly off the engine, I can check the heat riser operation later today and report back.

Turning the mixture screw only affects the fuel and air mixture at idle. Once the engine is running above 1000 RPM or so, the idle screw could be closed off entirely, or even removed from the carburetor without a noticeable change in the mixture. The main jet and the power valve controls the mixture at any speed above idle. The mixture screw is only used to get a smooth idle, and it has no effect whatsoever on high speed mixture or gas mileage.
Jerry

Here's a discussion on the heat riser which should be of help:
https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/850512/heat-riser-spring.html

Hello, Thanks again for all the feedback.

I tried to run her today but it seems to only be firing on one cylinder. The position of the heat riser does not matter anymore. I could not check for leaks as the engine was not running at all. The spark plugs are pretty white from the last 150 miles and I am still waiting for the new ones to arrive.

The engine was running hotter than normal because I was going trough mountains with about 50mph, but it ran with almost the same setup fine before. I suspect I lost the heat riser spring and from there it started overheating. What else can I look for?

To answer one of your questions, the counterweight on my 56 235 is on top of the shaft when in the heat on position (cold), and rotates toward the engine when things warm up. Mine was stuck in the heat on position for the first 3 years I have owned the truck, and I have not noticed any difference in how the engine runs with it now working. I did have a problem starting when the engine was hot that I think might be related to the valve, I will see how it does this summer. I think your issues are someplace else other than the heat valve.
Lee.

Yes, now it doesn't run at all so you need to look somewhere else.

So, it was running (albeit poorly) before you checked the plugs. Now, it doesn't run at all. Could you have mixed up the plug wires?

If you are 500 miles from home without your tools, you will probably have to get help. Tow it to a garage or get mobile mechanic.

Thanks again, the Counterweight may have been like that since I own the truck.

I arrived with the truck at my mothers place with the engine barely running at all. When I checked if it would run when cold it cranked fine, but only one cylinder fired at all. When I then checked the plugs I found some white, one black, some wet. The truck has a history of bad electric connections, if I hit a roadbump the gauges boogie for some minutes after.

I will bring her to a mechanic, but I don’t want to give up just yet and see if new spark plugs do something. I will also measure all electrical wiring involved in the ignition.

I have most of my own tools with me, but in Kiel I am part of a very large shared garage, so I don’t got some specific tools, like the vacuumeter and the timing light. I have the compression-tester though.

I am very glad to receive so much help allready.

Edit: I also will check if I put the spark wires right, but I think I did them right. I have some spare ones with me so I will replace them.

If one has intermittent gauges, likely have a poor ground. Check for loose connections, make sure wire contacts bare metal.

Ed

So I replaced the spark plugs wich expectedly did not change a thing. After sitting a while the engine started, but ran bad again and not for long. Compression testing the engine gave me values in the 130psi range on all cylinders. I ordered the entire ignition system to see if the problem lies there.

Edit: I did not order the entire Distributor, only cap and internal parts.

Edit 2: I tried to start the engine with starting spray, to see if it’s something with the carb, but it did not change anything.

Sounds like a good distributor refresh with NOS Parts is in order, then make sure your timing is right. My guess is your points have closed up some or your condenser went bad.

Alright, so I replaced the entire ignition system, and there you go, she runs again.

I want to thank everyone for the help and support!

I will replace the heat riser spring as soon as I can source one here in Germany, but it was not the issue and is stuck in the closed position because of the counterweight.

I did not have the patience to check the components individually, but I suspect the ignition coil failed (weakened) due to not having a ballast resistor (now has one) wich made it impossible for the electricity to run trough the corroded plug wires.

I hope this can help future bolters somehow.

Frohe Weihnachten und guten Rutsch

Max