I have a Speed Demon DP on my '83 Z28...I ended up tee'ing off the brake booster and PCV to the rear vacuum port on the carb....I had to block off the manifold vac. port because the carb didn't fit with the vac port in. The brakes just were very inconsistent due, I think, to it competing with the PCV for the vacuum from the same port. Could I tee the vacuum off the other vacuum source on the carb...it's a smaller port, but also has manifold vacuum. Has anyone else done this? My other option is to put a 1" spacer with a vacuum port.

 

You'll have to use the spacer or find a way to use the manifold port for the brakes.

 

Thanks,Apeiron....Yea, I almost rear ended a guy who stopped short...brakes felt like manual brakes!...no bit at all! Then at idle after i reved the motor to build vacuum...it was fine!...Can't go on like this! I think edelbrock makes a low profile right angle vacuum port......

 

The spacer would be an easy fix, if you have the hood clearance.
You could always go to the next step and tap into your headers to run pcv valves on both sides.



This is very old school, but it's been proven to produce more HP.
There is a thread about this somewhere.....

 

That works for race cars that always have enough exhaust volume to produce a vacuum. Not so much for street cars though, especially since it lacks a fresh-air source.

 

>I guess just venting the valve into the engine bay won't work? Or could I attach the PCV hose to the smaller vacuum port on the carb?....I could tee it to the vacuum advance to the distr.?

 

No, you can't use a smaller port.

 

One more solution that no one else gave is to connect the PCV hose to the fitting found on most air cleaners! You may need to knock-out to hole in the air cleaner housing and bolt on the fitting, but this is often the factory solution!

 

That's not a complete solution, and it's not how the factory did it on any car. The port on the air cleaner is to allow a supply of clean filtered air for the inlet side of the PCV system, not to draw fumes from the PCV valve. The PCV valve must be connected to an appropriate vacuum source.

 

Thanks for the clairification!....I know it's an environmental no-no, but one could just put a breather on the valve cover opening?

 

PCV isn't an emissions system, it's to evacuate blow-by gasses from the crankcase so they don't form acids in the oil.

 

itd be best to keep the pvc system cos it does keep your oil fresher but if it's not easily feasible i'd just delete the pvc and run a breather.

 

OK, I'm going with the spacer/vac port combo for the PCV.....and then using the Carb port for my brake booster......Thanks for the help, people!

 

Better to use the carb port for the PCV and the manifold for the brake vacuum.

 

Well, I finally got rid of the T'd PCV and Brake vacuum on my carb port! I put a breather on the valve cover and have the brake booster connected directly to the carb vacuum port....Now I have full power brakes all the time! To all you guys out there....you can't T-off the brake vacuum! Ever! The brake booster needs full manifold vacuum....undivided! It's dangerous to mess with this! I'd rather have brakes than PCV any day!

 

I had the same problem with my '83 with a Speed Demon carb. I used a 1/2" wood spacer under the carb, and a "low profile" 90 degree vacuum fitting for the intake. (Edelbrock and Spectre sells 'em)

I also used a 14" drop base air cleaner with a 2" thick element. I was using a air gap style intake, don't know what intake you're using. But my hood still shut.

-before I figured that out, I also used the old hose to the air cleaner trick. It was used extensively on older cars - but Apreiron's right - without a PCV valve. I just put a breather in one side, and another type of fitting on the other side that a 3/4' hose hooked up to, then the hose went to the knock-out on the air cleaner base lid. That's what the knock out is there for. It helps scavenge the air/oil blowby to the carb, but not as well as a PCV valve will.

Just running breathers in each valve cover will work, but your oil will get dirtier quicker that's all. We change oil too often anyway.

-I almost rear ended a car too trying to tee off my PB and PCV...lol - never again!

 

I do this all the time with cams much larger than what you are using and don;t have a problem with the power brakes.
But there are some critical differences in how I set things up to maximize available manifold vacuum and stablize it while idleing in gear.
I also checked and verfied that the PB booster and check valve and hoses were not leaking or collapsing. It makes a big difference.
If you employ manifold vacuum advance to get your idle spark advance, thats half the problem.

I just installed my holley/proform carb (removed the edelbrock) and had to T the PB/PCV vac line. It works fine, as it always has with the PCV and PB T'd on the same vacuum source on the carb base.

What camshaft are you using and how do you set up the spark timing.

It's all in how you set it up and check the details. I don;t even run a vacuum resivior canister althou thats not a bad idea. (requires the proper in line 1 way check valves to work properly.)

 

F-Bird....I'm running a small cam....ZZ4...I get 20" of vacuum too! but I tell you, Teeing off the brake vacuum is dangerous on a street car! Sure I have brakes at idle.....but try accelerating a bit and then quickly slamming on the brakes...like on a panic brake situation...You'll have no brakes at all!

 

Thanks Confused! So, the Edelbrock thing fits under the Demon DP? Yea, using breathers for now, but if this Edelbrock thing works, I'm gonna have to get one and then run the PCV too. I got the RPM Performer intake on...not the air gap...is that higher? Don't matter to me.....using a Daytona turbo hood with good clearance. Say, did you ahve trouble wih the throttle staying at idle? For some reason, my blades stay open just a bit and I find myself idling at 1,000 instead of 600.....It goes back down if I blip the throttle...and I have the springs on the throttle bracket all the way over. The pedal is actually a bit too stiff for me the way it is now....but it's either that or the idle going to 1500! Is the vacuum keeping it open? It snaps shut with the engine off. Oh, and my Demon has no choke...so that's not the problem.

 

wdigitog - Remember, I used a 1/2" spacer and the low profile 90 degree fitting for my PB and it works fine. I used the large fitting on back of the carb for the PCV. My stock hood still shut. So if you have a Daytona hood (I like those BTW), along with a performer intake (lower than air gap I think) - you should be able to run a 3" thick filter element on that air cleaner which shouldn't hurt anything at all. Glad I could help!

P.S. - As far as your linkage goes, I don't really know. Just ensure it's a nice straight line pull between the cable and carb linkage arm and it shouldn't be binding. I used my stock bracket back then, I just bent it a little to adapt to the intake. Good luck with it!