Vacuum Question

[mikester]

Nothing ?

 

[fleming442]

Usually, the 2 ports on the side are 1 ported vacuum and 1 manifold vacuum.

Ported vs manifold vacuum advance - The BangShift.com Forums

QandA for everything mechanical

bangshift.com

 

[mikester]

Usually, the 2 ports on the side are 1 ported vacuum and 1 manifold vacuum.

Ported vs manifold vacuum advance - The BangShift.com Forums

QandA for everything mechanical

bangshift.com

Just looking through that thread quickly it deals with vacuum advance unless I missed something. I have a mechanical advance distributor.
I need to know if the manifold vacuum fitting can be split and run to the PCV and booster. I only have one manifold vacuum fitting so far. My carb has two small barbs on the base. One in the front and one on the right side which I assume would have gone to the distributor. I dont think it will work for the modulator on the TH400. I was thinking about drilling under the carb on the right side of the manifold for another line. Will that work ?

 

[fleming442]

I don't know that I would tee the PCV and brake booster because if the PCV sticks open, you lose vacuum to the brakes? Then on the other hand, how is that different than having it to 2 ports on the base of the carb? Interesting conundrum for sure.......

I was suggesting that you use the small ports for the trans governor. The PCV and booster need volume, so that's why they're 3/8 vs 1/8 line sizes.

 

[mikester]

I don't know that I would tee the PCV and brake booster because if the PCV sticks open, you lose vacuum to the brakes? Then on the other hand, how is that different than having it to 2 ports on the base of the carb? Interesting conundrum for sure.......

I was suggesting that you use the small ports for the trans governor. The PCV and booster need volume, so that's why they're 3/8 vs 1/8 line sizes.

So you think I can use the larger port on the carb base for the modulator ? Odd that its the larger of the two on the base but much smaller than the barb on the modulator. I hope I can get a line to stretch over the larger barb.

 

[fleming442]

Large on the front to PCV and small to the trans; see what happens.....

 

[bracketchev1221]

not sure if this applies to you !,have a high rise intake! I drilled the intake just under the carb gasket and ran my vacuum from there

This is another option. Drill the intake and put ports where you need them.

 

[84cutspreme]

You can always add in a manifold. at one point i had msd setup and was using map sensor for timing. I needed extra port too. I had the 3/8 line run to manifold and out to comp cams storage tank then to brake booster. off the manifold I had line go to map sensor, and another line go through 3-way check valve and factory storage tank for ac/heat control. had no issues and manifold was off 90’s mustang

 

[mikester]

Large on the front to PCV and small to the trans; see what happens.....

The large port on the carb is pretty small. Maybe 3/16". The front port is maybe 1/8" The only 3/8" vacuum port I have on the motor is the one under the rear fuel bowl and its not on the carb, its threaded into the manifold.

 

[mikester]

You can always add in a manifold. at one point i had msd setup and was using map sensor for timing. I needed extra port too. I had the 3/8 line run to manifold and out to comp cams storage tank then to brake booster. off the manifold I had line go to map sensor, and another line go through 3-way check valve and factory storage tank for ac/heat control. had no issues and manifold was off 90’s mustangView attachment 133012View attachment 133012View attachment 133013

The big question for you is how big was your cam ? Watch the video of my car running in my build thread. Its right at the edge of not having good vacuum. The folks at Comp Cams said this was the biggest cam that I could use and still run power brakes and an automatic.