[4spdChevelle]

Hello, I had a carb rebuilt (7042220) and I don’t have vacuum at any of the ports. The choke pull off does have vacuum there but I’m trying to get full manifold vacuum for my distributor vacuum advance. So I can’t adjust the idle mixture screws since my gauge doesn’t read anything. I’ve tried seeing if my gauge was malfunctioning but the ports are clearly not sucking when I uncap them. The gasket is on correctly but what seems to be the issue? Could they have been blocked during rebuild?

 

[77 cruiser]

They could have got blocked if the wrong gasket was used. You have 1 for the pulloff , 1 is ported maybe & the other manifold. Does that sound right?

 

[540 Olds]

I'm guessing 77 CRUISER is correct about wrong gasket; you can cut a small "gap" in the gasket to get vacuum. I've "ops checked" this highly technical modification.

 

[4spdChevelle]

They could have got blocked if the wrong gasket was used. You have 1 for the pulloff , 1 is ported maybe & the other manifold. Does that sound right?

I’m using this gasket that came with the carb from the builder. I’ve used it before it got rebuilt and this wasn’t an issue. The carb base plate wasn’t changed.

 

[4spdChevelle]

I'm guessing 77 CRUISER is correct about wrong gasket; you can cut a small "gap" in the gasket to get vacuum. I've "ops checked" this highly technical modification.

Are you referring to the gasket for the air horn?

 

[77 cruiser]

No between the main body & base. the one about an 1/8 inch thick.

 

[blm]

No not the air horn. Vacuum is created beneath the carburetor. What about the large port for pcv or power brakes. Is there vacuum there?

 

[4spdChevelle]

No not the air horn. Vacuum is created beneath the carburetor. What about the large port for pcv or power brakes. Is there vacuum there?

The large port in the front for the pcv has vacuum and the choke pull off has vacuum. There is not a large port in the rear for power brakes. I use a fitting on the manifold for power brakes. Numbers 1 and 3 do not have vacuum.

 

[77 cruiser]

I think 3 is ported. So it wouldn't have vac. @ idle if that was the case. Who did the rebuild?

 

[4spdChevelle]

I think 3 is ported. So it wouldn't have vac. @ idle if that was the case. Who did the rebuild?

Yeah, I’m trying to use #1 but Cliff Ruggles. He did an amazing job, the car performs completely different. He doesn’t work today so I can’t get in contact and I’m just trying to figure this out.

 

[77 cruiser]

If Cliff did it should be right. Cliff likes ported, so.

 

[blm]

Should be fairly easy to figure out. Remove the carb and look for where the vacuum is drawn for the #3 port. It is most likely blocked by the gasket or it is plugged.

 

[Humberd]

Do you have vacuum at the large ports
Like Pcv & power brakes ?

 

[LeoP]

How about on the back of the carb??

 

[4spdChevelle]

How about on the back of the carb??

There is only one fitting at the top of the carb in the back but that does not suppose to have vacuum and it does not. The pcv and the choke pull off have vacuum but numbers 1 and 3 do not. I’m going to try and contact Cliff tomorrow to see if he blocked the ports off but as of right now I teed into the port for the choke pull off for the vacuum advance.

 

[77 cruiser]

He answered on his forum. Just blow air in them & see if you can tell where it comes out. I thin the front is ported & the side is manifold.

 

[Humberd]

He answered on his forum. Just blow air in them & see if you can tell where it comes out. I thin the front is ported & the side is manifold.

Yes

 

[77 cruiser]

Did you see what that other guy said?

 

[4spdChevelle]

Did you see what that other guy said?

No, I did not. What does blowing air in the ports and seeing where it comes out do?

 

[540 Olds]

4 SPD Chevelle asked :"Are you referring to the gasket for the air horn?"

No; when I wrote my original reply I did not realize you had a Q-jet..My comment was for Holley metering plate gasket..sorry for confusion.