My 1967 352 is still not running right. The vacuum control had a hole in it so I replaced it with a new one but it still falls on its face. It has a new carb on it. It idles good though. While it is idling I can take of the vacuum line and it doesn't affect its running. Isn't it supposed to idle rough? Any ideas what the problem might be?

 

Truckman,

If you have the Vac advance hooked up to the ported Vac on the carb then your findings are normal. There is no Vac signal at idle. As soon as the throttle opens there is Vacumm. If you have it hooked up to manifold Vacumm you will see a difference when it is unplugged as there is a large Vac signal there at idle.

As for the stumble, does it happen when you first get on the gas? If so make sure your Accl pump linkage is set correctly. The Holley web site has some good info for this.

Hope this helps,
Lee

 

Thanks for the reply.

No, it doesn't do it as soon as I get on the gas. I just can't figure out what would cause that. I have replaced everything on it.

 

Hi,
I reckon I need more info.
When does the stumble occur? Does it make a differance hot or cold? What exactly happens? backfires? Burps? or just low power. Has the float level been checked?

Lee

 

Maybe you got a carb with a bad accelerator pump.

 

It doesn't make a difference hot or cold. It doesn't backfire. Just low power. I rebuilt the engine the past spring. It was running real smooth.. Put everything new on it. Got up one cold morning to go rabbit huntin and it acted up. I checked the vacuum advance control. It had a hole in it so I figured that was the problem. Replaced it but the problem remained. The problem is that it idles fine but when you slowing push down on the gas it will start to speed up and then it will like fall on its face.

 

I'm sorry, friend, but when you say you replaced everything, that still doesn't provide enough info because that leaves many things open to assumption.

When you slowly step on the throttle and reach the point that it falls on its face, will it recover at all if you continue increasing the throttle? If not, I would check to make sure that the springs on your centrifugal advance are still in place and that the weights aren't frozen in place with rust. It sounds like your centrifugal advance is not working.

Good Luck-

Joe

 

When it falls flat try pumping the gas real fast a few times and see if it recovers. It could be that you have the accelerator pump rod in the wrong hole, not giving it enough of a shot now that it is cold out, to richen the mixture.

 

It will recover but it still doesn't run smooth.

 

I figured out something else maybe you all can help me with. It has a manual chock. I can pull out on the chock a little and it seems to run right, at least it doesn't fall on its face. Perhaps I could put some cleaner in the gas tank and that would take care of it? Would appreciate any advice..

 

Suggest you eliminate the basics at first.
1. ignition timing at idle and full advance
2. fuel pump pressure. fuel flow test.
3. float level
4. engine vacuum
5. compression check
6. restricted exhaust

 

 

>I figured out something else maybe you all can help me with.
>It has a manual chock. I can pull out on the chock a little
>and it seems to run right, at least it doesn't fall on its
>face. Perhaps I could put some cleaner in the gas tank and
>that would take care of it? Would appreciate any advice..


It sounds to me like you have one of two problems. First is that you have a vacuum leak. By pulling the choke you are equalizing the difference between the leak and the normal air flow. Listen for a hissing sound with the truck ideling. If you cannot hear anything then try the WD-40 trick. With the engine running, spray WD-40 around all your vacuum connections and the carb base plate. If you hear the idel increase you know where the bad hose/connection is. Be sure that you look under the dash for any bad-lose vacuum lines also.

Second you cannot find a source of a vacuum leak than it could be that the idel bleeds in the carb have become blocked/clogged with junk over the years. This would make the engine run lean. When you partially close off the choke you are richening the mixture to where it is close to correct. The only way to tell if this is the case is to remove, throughly clean, and reinstall the carb.

 

My Truck does similar when slowly pushing pedal down. Mine does it the worst when it is cold outside. I think if at anytime you have a backfire through the carb then you may have a bad power valve. You could also be running a little rich and when the rear barrels begin to open it could overwhelm engine with fuel. But, it sounds like from the earlier posts you definitly have a vacum leak. Or the vac advance is hooked to the wrong type of vacum.

As stated before a very detailed discription of the problem would help the most. The reason is there are too many possibles to rule out. Good luck in the diagnosis.


Scotty