Rochester 3x2 set on 348 on my Model A Pickup

[Noel Edgar]

Hello out there,

As a novice I am trying to pick some brains to keep my 348 running reasonably well. I have had it for just over 2 years and it has been an "off" again "on" again relationship. The motor is a little tired ( I have been told by a local mechanic who everyone says is good at his trade). I am trying to learn and understand how to do small things myself. My question revolves around the air mixtures on the center carb. I read somewhere that to set the air mixture you start with the screws in and turn them out approx 1.75 turns and then adjust outward until the motor is running smooth.

If someone could add to that to make it clearer or offer some more info I would be greatly appreciative. Please remember that I am a novice.

Thank you.

Noel

 

[Don Jacks]

1 1/2-2 1/2 turns out from lightly seated is a good starting point for that adjustment.Then use a vacuum gauge,or a tachometer and adjust in or out to obtain the highest steady vacuum reading,or highest rpm.

 

[LMBRJQ 60]

Correct me if im wrong Don but if this is a tri power would Noel have to determine if he has leaks at the front and rear carb also or should he blank them off fitst then adjust the center

Might be a mile off here, usually am

Steve

 

[Don Jacks]

Not if it's a fairly decent running engine.Start with the basic idle speed/mixture adjustments.If those adjustments don't bring it in,then start looking for air leaks.

 

[Noel Edgar]

Thanks tom you both I will use you advice and see where it takes me - I currently have them at approx. 1.75 turns (also new plugs Ac Delco R45 Xls at .35) and the truck is running not bad. Not sure but I think the new plugs are the main contributor right now.

Thanks again for your advice.

Noel

 

[Fathead Racing]

Part of the three two puzzle is ignition timing. Using manifold vacuum at the vacuum advance can will advance timing at idle after setting initial timing. This allows you to turn the curb idle screw in closing the throttle blades to a point that you are out of the high speed circuit and into the idle circuit where you belong. This cleans up the idle very nicely. If you are not using the vacuum advance get an advance kit and set your initial to at least 14 degrees advance initial.

 

[Don Jacks]

What seems to be the problem with the way the engine is running now?

 

[DonSSDD]

Not if it's a fairly decent running engine.Start with the basic idle speed/mixture adjustments.If those adjustments don't bring it in,then start looking for air leaks.

Don, an air leak would show up in the vacuum gauge with it being all over the map?

 

[Don Jacks]

It would depend on the severity of the leak.A relavity small leak can cause a drivabilty problem off idle,in the mid range.A base to bowl gasket leak wheather from bad gasket,or loose screws that allow the body to shift when the accelerator is moved comes to mind.Most of the time,a vacuum gauge will read low,and dance around a bit.