Distributor Vacuum Line from the Center Carburetor

[MoparHonda]

I have a '70 Plymouth with a factory 440 six pack. The vacuum hose to the distributor comes from the center carburetor.

There is NO vacuum in that hose, no matter the speed of the engine. I never get vacuum at idle, acceleration, or running at higher RPM. Had the carbs rebuilt by National Carburetor, still no vacuum at any time.

Why do I have no vacuum? How many pounds of vacuum should there be?

 

[WileE]

Run manifold vacuum. Ok, now the can of worms has opened.

 

[62MAX]

I have a '70 Plymouth with a factory 440 six pack. The vacuum hose to the distributor comes from the center carburetor.

There is NO vacuum in that hose, no matter the speed of the engine. I never get vacuum at idle, acceleration, or running at higher RPM. Had the carbs rebuilt by National Carburetor, still no vacuum at any time.

Why do I have no vacuum? How many pounds of vacuum should there be?

Is it connected to the metering block and is it the correct block ? There is no vacuum at idle,you should only get vacuum once the throttle plates are above the transfer slots.

 

[440+6]

There are two nipples on the center carb the upper is for the distributor and the lower for the outboard.
The upper should have no vacuum at idle, when you open throttle it should have vacuum.

 

[MoparHonda]

Thank you for your help, that's the way I have it, the upper hose to the distributor and the lower one to the outboard carbs.

I have no vacuum at idle and also NO vacuum with the throttle open. I never get vacuum, regardless of how far the throttle is opened or for how long the throttle is opened.

 

[62MAX]

Thank you for your help, that's the way I have it, the upper hose to the distributor and the lower one to the outboard carbs.

I have no vacuum at idle and also NO vacuum with the throttle open. I never get vacuum, regardless of how far the throttle is opened or for how long the throttle is opened.

Any chance of getting a picture and number on top of the block? The block should be numbered 6020 if it an original 70 block.If you have no vacuum at all the problem is with the block, main body or body to base gasket.

 

[MoparHonda]

I do not see any numbers on top of the center carburetor's metering block. I DO see the number 5925-3 on the driver side of the metering block.

Any way to isolate where the problem is, the metering block, main body, or body to base gasket?

 

[440+6]

Are you testing from the port itself or from the end of the hose?
Some people block off the vacuum advance be shoving a bb down the hose then connecting it into the distributor to make it look stock.
Or you may have some blockage in the carb.

 

[MoparHonda]

Testing from the port itself.

FYI: The hose is clear, I removed it from the car and can easily blow thru it.

if there's blockage in the carburetor, how would I go about clearing it? Blow compressed air thru the hose into the carburetor?

 

[440+6]

You may have a gasket (base to body or metering block) blocking the port.
I would disassemble and clean and blow out all the passages then re assemble making sure all the gaskets are correct.

 

[MoparHonda]

Thank you, 440+6, a gasket blocking the port may be the issue, no way to know other than to tear it apart and look.

The port may indeed be blocked, I cannot blow thru it with my mouth, regardless of the throttle position.

 

[moper]

Tak some carb clean and spray into the nipple while looking down the carb's throttle bore. If nothing is seen from the slot just above the transfer slot, there's a blockage. You can try shop air, but if it won't clear you can remove the metering block and try to clear the passage with wire or something.

 

[62MAX]

I do not see any numbers on top of the center carburetor's metering block. I DO see the number 5925-3 on the driver side of the metering block.

Any way to isolate where the problem is, the metering block, main body, or body to base gasket?

That is not the correct block,take it off and check if the port has a open to the passage to the inside of the block.

Here are the three metering block gaskets that cover about everything,if yours does not match the bottom black one ,it is wrong.

 

[MoparHonda]

Thank you, '62 Max, I'm gonna take the carb back to to National Carburetor and have them take a look since they're the ones who rebuilt it. I'll give them your picture and info, see what they say.