Hey everybody. I am trying to work out a solution to my vacuum issues and after searching all over I am still confused. Here is what I have going on.

I recently went from a 2brl setup to 4brl using a Edelbrock performer RPM intake manifold and a Holley 80457 carburetor. When I installed the intake manifold I did not drill and tap the spot at the back where you can run the PCV into. The reason being the Carb I got had a PCV vacuum port on the back. Here comes the issue. After I did this work one of my wheel cylinder went out in the front and I decided to swap to disk brakes (65 F250 to 78 F250 dual piston discs). I also went with power brakes and that is where the problem comes from. My carb has a back PCV or Power Brake port, a side distributor port, and 2 front full vacuum ports. How do I hook this up right?

I found online that one option says to T the rear PCV/Power brake port, 50% say it has worked for them for years and the other half say they had no brakes after trying it. The next option is to run it off the Front full vacuum port but I have been trying that and sometimes I kill the truck when I apply the brakes. The other way I ran was the PCV in the front and the power brakes on the rear but that does not seem right and I have been told by 2 people that is a bad idea. The last way is to drill and tap my carb spacer in the back and run the brakes or PCV off that new port.

From your experience what is the right method or is it just works for your motor.

I am new to working on these types of motors and find it much different from the water cooled VW's I used to play with.

Thanks,
Ben

 

Drill and tap the spacer.

 

That intake should have a vacuum port on the top of the drivers front runner. You can't get better vacuum than that. Also I heard (but never saw) there is a port on the back of the intake.
puttster

 

puttster, I do have that vacuum port but it is being used for my transmission now. I wonder if I could run the transmission off the small front vacuum port on the carb? Right now my plan is to pull the carb and drill the spacer and hook it up that way.

As for the back vacuum port on the intake. There is a spot to drill and tap for one but I did not do that when I installed it and do not want to pull the intake manifold off to do it now. I'm not lazy but that is a lot of work and it is not leaking now so I would hate to add a leak if I did remove it to drill.

 

Back port is where the brake booster is supposed to be fed from.

 

That intake port should do double duty - for booster and transmission. On my 65 a oretty thick hose runs to the check valve on the booster, where there is a "T" that runs to the Tranny.

 

Absolutely correct. Make sure you have the check valve.

 

So that is 2 for the back of the carb spacer and 2 for T'ing off of the #5 intake runner.

I was planning to drill and tap the spacer today but now I have a tie on the correct way this should be run.

 

Double post

 

I drilled the carb spacer this weekend. Have not had a chance to drive it since I ended up doing a 3G alternator swap this weekend on it also. I will let you know if it fixed the issue.

Ben