vacuum source?

[sal3030]

Hello,
I rebuilt my Mercarb on my 4.3Litre today. Everything was fine out of the water but after putting it in I kept having problems. One of which, I fixed, the float was set to high although I followed the instructions to the letter (27mm). The carb kept flooding, now it is vapor. The second thing is, where can I get a vacuum source to connect my guage to? I don't like setting the air fuel mixture by ear. Thanks.
Sal

 

[Don S]

Re: vacuum source?

Look on the intake manifold for a plug. Temporarily remove it and install a hose barb fitting for your size vacuum hose.

 

[sal3030]

Re: vacuum source?

I did look, my father who is an auto mechanic couldn't find one either, he said there has to be something. I do see a hex head plug in the intake manifold at the base of the carb that we missed before, What about that? and would you happen to know the thread? 3/4npt ?

 

[eldplanko]

Re: vacuum source?

3/4 NPT is pretty dang big.... you sould be looking for something closer to 1/4 or 3/8 NPT at most. Unscrew it and see where it leads to.

 

[sal3030]

Re: vacuum source?

It leads into the throat of the thottle body at the intake manifold. Otherwise there is a typical diamond shaped cap that may be where a EGR would be mounted if the intake was used on a car. I hate to start unscrewing everything. You're right, it is more likely a 3/8 ntp.

 

[sal3030]

Re: vacuum source?

I tried to remove it. The 1/4 Hex is too small, and the 5/16th too big. It must be 7mm. Does this sound like something I should pursue? Then will the threads be ANSI NPT ?