I am really stumped on the fact that there is no place to hook the power brakes up with this carb...I have my distributor vacuum line, PCV valve line, and tranny vacuum line but leaves me without a power brake hook up....WHAT DO I DO NOW!!

 

There should be a large vacuum port at the back of the carb at the base. You can take vacuum from the intake manifold also.

 

The Street Avenger carbs have both a PCV and brake booster port, but the old "regular" universal carbs don't have the port in the back.

 

There should be 3 ports on the carb. Small full time vacuum and a ported vacuum up front and a larger full time vacuum out back for PCV. I had to run a spacer to use the tapped hole that is on the rear of the intake.

 

Correct.

The "regular" Holleys don't have the port in front.

 

I also ran a spacer so I could run the line to the manifold.

On my Edlebrock I had problems wunning the brake vaccum line to the carb. Under heavy braking the car would want to die. When I switched it to the manifold that cured the problem.

 

I just run a T in the booster line for the PCV and run both off the back port. Haven't had any problems yet.

 

Do you guys think I will be alright with just running a T?? I am using a pretty good cam in my engine so I dont know??

 

I used a t fitting for my lines and guess what?? No POWER BRAKES...yippie!!!

 

PCV is a constant leak. It needs to go to the carb base (not a runner).

Power brakes require a solid vacuum signal. Since it isn't a big air inlet source, it's okay to tap it off of a runner. But, it can't tolerate being tied to the constant leak.

 

you cant T the PCV with any other Vac device. the PCV is a controlled leak, so the other device gets no signal.


hook the PCV up correctly. if it was me, id drill and tap the manifold plenum below the carb...

 

The whole problem here is that with a double pumper the vacuum inlet on many intakes is not accessible because the back bowl hangs over it. In fact when I switched to DP I had to grind down the pug I was using to plug the hole so the carb would fit.

.

 

Yeah I had to do the same thing. I am thinking about getting a 1" spacer for the carb and using a 90* vaccum fitting using the hole I just had to plug do to carb clearance.

 

ANother option would be to modify your carb spacer plate. Our 950HP carbs have no vaccum ports so our only option was to drill and tap a 1/4" NPT hole in the spacer. Quick, easy and it works.

 

IHI,

Thats what I was thinking about doing this morning. I have to wait till tommorrow when the spacers comes in but I was thinking about drilling and tapping the spacer so I could hook the PCV in that port and hooking the brakes to the back port.

 

With my old motor I was just running a plastic 1" 4 hole spacer. If this is the case with you or what ever 4 hole spacer, be sure to set the gasket on it from the bottom to see if you have to notch into the gasket material to get a vaccum signal. With my plastic 4 hole it also had 4 hollow regions between the holes, but the gasket covered these areas entirely. I talked to my head guy in town and he said all I needed was a opening about the size of a pencil for vaccum. So once I took care of drilling and tapping the hole I took a razor and cut a small notch in gasket that covered this area but not did'nt cut enough away to make it not seal against the intake.

Before i installed the 1/4"NPT barb fitting into the spacer I went and dabbled it with red silicone to be sure it sealed and let it set up before running. Off this 1 barb fitting I then ran a chunk of hose with a 3 way fitting/splitter, 1 to the brake booster, 1 to the TH350 modulator, and 1 to the PVC in the valve cover. Worked like a champ.

To anybody using these pletonic (plastic) spacers be very careful when tapping as these are very brittle once you get into it. Drilling them is very easy, just be sure to center you hole in the hollow area so once you go to install your tap it will be centered in this hole, otherwise you'll have problems if it's too high or too low since it wont have much material for the threads to grab. Also should note these spacers unlike plastic that usually break or crack when stressed, these simply flake off is the best way I can put it. But when they flake off it's usually good size chunks that flake off so when tapping go slow and back it out often when threading it in to help aliveate some of the stress.

It would be much simplier with an aluminum spacer since it's metal but you still should use caution when tapping with a NPT tap since it's easy to wipe out the threads you've already cut. The NPT taps can be had at Home Depot-whereI got mine anyways. Came with a 7/16" drill bit and the 1/4" NPT tap for $13. In the future you'll find all sorts of uses for NPT taps so they're a good investment anyways. You can tap you own drain plugs/vents in rear end housings, drains in cast tranny pans, places to install electric sending units, etc...very versitale.

Good luck.

 

Thanks IHI I will be using an aluminum 1" spacer. That is some very useful info and I thank you very much for the help.

 

i have a holley carb on my 350, and i just put a t-splitter for the power brakes and the pcv. works pretty good, except the car seems to want to stall under very hard braking.

 

I solved my problem by buying a already ported 1" spacer.

 

Exactly what happened with mine! Switched it to it's own source on the intake, (added a 1/2" wooden spacer) and all is well now.

 

you guys with the spacers...can a spacer, a holley, and a 3" element (1 1/4" drop base) fit under a stock T/A hood?

 

This was my thought also.

 

Well, I have a 1/2" spacer, a Demon carb on a "Crosswind" (Air Gap) intake with a drop base air cleaner.

And it all fits under the stock hood.....barely. But that's using a 2" tall filter element BTW. Don't know if a 3" would fit......