CamarosRUS

Opinions on where to tap into the manifold for my PCV setup?

Either:

1. #3 intake runner nitrous boss

2. Drivers side of plenum

(You can see a couple black marks where I am debating between)

CamarosRUS

1fastam brought up a good point...

If I tap into the nitrous boss will this possibly lean out the #3 cylinder by adding extra air into the runner?



BTW is my carb supposed to lean forward like that?

F-BIRD'88

Your carb is bent!!!!!

I've been running my pcv "T" ed into the same vacuum source at the back of the carb as the power brakes. Works fine.

CamarosRUS

Yea I think I remember you saying that in another thread, however, when I T'ed mine in I lost 30% of my stopping power. Plus, with this new cam I should have even less vacuum, I don't want to risk it.


I'm still racking my brain trying to figure out if T'ing the brake booster line into the PCV line (booster line before PCV valve) will provide more vacuum than T'ing the PCV line into the brake booster line (PCV valve before booster line).
But I don't think so.




BTW...I like the big bold red font.

Damon

I think they sell a flat 90* vacuum fitting you can screw into the threaded hole that's already in the plenum behind the carb. Helps with clearance issues when you're using a Holley-style carb.

CamarosRUS

The best thing (that I've read about) is Edelbrock's $20 lo-profile fitting that still needs a 1/4" gasket to clear. Plus, the Speed Demon has it 3/8" nipple facing rearward IIRC close enough to Edelbrock's port to cause interference anyway.

F-BIRD'88

You're not getting enough manifold vacuum at idle because you're not running enough initial base spark timing at idle. Its all in the setup.

The recent Holley/Weiand AIR STRIKE intake manifold has the vaccuum fitting port in the correct position on the #8 intake runner to allow space for the holley carb. Thats where your PB's are supposed to be connected to. (as long as your PB's don't leak vacuum).

The best solution would be to TiG weld a aluminum bung boss on to the #8 runner like on the Weiand manifold. Then send Vic JR. a nasty email.
Don't know what Edelbrock was thinking.

What camshaft?

CamarosRUS

Why would the PB's supposed to be connected to #8? Mine will connect to my rear port on my carb and the PCV to wherever I tap. While I'm not going to TIG weld a bung, hopefully one of the injector/nitrous bosses will suffice if the plenum wouldn't be a better choice.
I don't know what they were thinking either except maybe more money going with their carbs or their "lo-pro" fitting.

Cam is 242/248 .576/.600 110 LSA and 106 centerline

chevymec

iTrader: (5)

I went to lowes and got a brass adapter and a plastic/nylon 90 fitting. hooked my PB to this and my PCV to my carb.

CamarosRUS

Where did you happen to screw the brass adapter and nylon fitting into?

online170

If you look at the actual RPM air gap manifold, it is tapped on the #8 cyl anyway.
http://www.edelbrock.com/automotive_...r_gap-sb.shtml

Also, look just below at PN #7516 the vortec design, which has it much further back like the weiand.

Dont spend money on that stupid 90* edelbrock fitting. I was so angry at how expensive it was, and then i learned its ONLY SUPPOSED TO WORK WITH EDELBROCK CARBS..... Which dont have any intrusions in that are anyway... On top of this, it WILL NOT fit under your carb without causing a 1/4 gap at the back, and it will not allow your PB fitting to screw into it either. You will need adapters. At least, it was this way for me.

Also i think your carb is tilted, because it is hitting the manifold already. Check back there, and make sure your "squirter" (squirter = BG demon, pumper = holley) isnt hitting the manifold. You may have to run a 1/4 in gasket anyway.

F-BIRD'88

The rear port on the carb base is for the PCV. Look on all factory carbed SBC and BBC intake manifolds. The P/B's and transmission vacuum modulator connect to the port on #8 cylinder runner because no appreciatable vacuum airflow is drawn to effect the runners AFR. (as long as the PB diaphram does not leak air)
{Test your P/B vacuum booster for leaks.}
Where as the PCV flows some air all the time so you want it shared by all eight cylinders. Therefore it is connected to the carb base or plenum right beneath the carb.
If you were to connect the PCV to the # 8 runner or any other runner, you will leanout that cylinder and create detonation on that cylinder.

If you are going to drill and tap anywere drill on top of the #8 runner and tap it for a plumbing fitting. Connect the brakes there and the PCV to the carb base.
Edelbrock carbs have a spot front and back of the carb base for two 3/8" hose barb fittings. (most holleys don't).

You want a lot lot lot of timing at idle for that cam to maximize available manifold vacuum at idle and optimize the idle quality and throttle response.
I run mine with locked out centrifical timing 36deg all the time. + ported vacuum advance for cruise. approx 10 to 12deg at max cruise.
I have never exhausted the P/B's vaccuum and lost the P/B boost assist.
Try it.

A alternative way to connect the PCV is to drill and tap for pipe to 3/8" hose barb fittings into each side of the manifold plenum as in the diagram. and "T" the two connections together, then connect the PCV to the "T"
This way you ensure the PCV airflow is equally shared by all 8 cylinders.
If you just tap into 1 intake runner you will cause that cylinder to run lean.

Want to build a better mousetrap? Connect the PCV to a remote (firewall) mounted PCV oil/air separator. Then connect that to your PCV hose T. A common $3 paper element fuel filter with 3/8" hose barbs on in and out will do just fine. mount it vertically on the fire wall. Replace it with a new one periodicly/ as nessessary.

online170

DAMN! I wish i knew this, might explain my my cyl 8 is about 20 psi low on compression in comparison to the rest (164ish). Im switching this as soon as my car gets back on the road.

Air_Adam

I did exactly this with the same intake. Drill and tape the nitrous boss (any of them) and tap with a 1/8" NPT tap. Then, depending on whats around the runner you drilled, you can do 1 of 2 things:

A) Thread in a fitting with a 3/8" barb and 1/8" thread, pointing straight up, and call it a day.

B) Get a 90* elbow fitting with a 1/8" male end and 1/8" female end. Thread the male end into the manifold untill its tight and/or the female end is pointing in the direction you want the barb to point. Now thread in the 3/8"-barb-with-1/8"-thread fitting from option A into your elbow.

I went with option B and I've never had any problem with it. It points straight back, and you pretty much can't see it as its mostly hidden under the throttle linkage. You can sorta see it in this (the only) pic I have. Look under the throttle bracket for the brass fitting:

Supervisor42

We seem to have lost our way on what the factory did and why. The PCV is put in right next to the idle air flow to maintain a consistant idle mixture. This prevents the PCV air from leaning out some cylinders more than others.
The power brake booster is connected at the rear barrels where the vacuum is the highest at part throttle.
The port on the #8 runner is for the vacuum accessories because it flows almost no air at all.
(see attached pictures)
The best locations for the aftermarket carb setup will be to get as close as possible to these original locations to keep from upsetting the mixture balance in the manifold and maximizing the power brake performance.
For example: drilling into the front of the manifold into the plenum divider so the PCV flows into both planes equally right below the idle flow.
The power brake circuit may be able to be added as a mirror image of the front.

chevymec

iTrader: (5)

I thought "squiters" went on top of the carb regardless of what brand??

CamarosRUS

This has become a very informative thread, thanks guys!



After doing my research I think I will not tap into the manifold but make my 1/2" spacer work and take advantage of the rear port on my carb for my PCV and use the factory Edelbrock port on the #8 runner for the PB. Hopefully this 1/2" spacer will be sufficient.
This seems to be the safest and "best" way to go about running these lines since I do not want to lean out any cylinders and want to take advantage of the most vacuum for my brakes that I can. Unfortunately my carb does not have two ports for both the PCV and PB.


Air_Adam...Thanks for the leg work and pics man, it helped a ton!
online170...IIRC it wasn't interfering but I will check again for sure.
F-BIRD'88...I plan to run a baffled grommet and also run an inline fuel filter to keep as much oil from getting into the carb/manifold as possible. I will have to tweak the timing since I am at or over 11.1:1 CR but am contemplating the idea of a vacuum pump.
Supervisor42...excellent info man, thanks!

online170

Yes youre correct.

You are referring to the part that "squirts" that is the squirter, but the part i was referring to, is the pump for the squirter. Its al part of the same system.

Its a trademark thing;

Holley = Double Pumper
Demon = Double Squirter

The single pumper/squirters, dont have that pump at the bottom of the rear fuel bowl, so they dont cause interference.

kowboy59

iTrader: (8)

make a T and get a vacuu, canster. end of story thats how mine is set up and i brake fine

CamarosRUS

Online170....don't know if you have any other suggestions or if intakes are supposed to be this way but the intake itself is slanted downwards towards the front of the motor. It is all bolted up and you can see (without the carb on it) the intake tilts forward

Any ideas?

Confuzed1

iTrader: (4)

It's supposed to be that way. You should see how my carb sits on top of my blower! They're all like that. I think it helps prevent the rear jets from running dry during hard acceleration. Sometimes jet extensions are used too.

Problem is, whether you use the "expensive" Edelbrock fitting or the cheaper "Proform" fitting, you'll still end up needing a 1/2" spacer under the carb or else your secondary acc. pump arm will hit the fitting. Those ports on aftermarket intakes are in the dumbest place. I used a Prof. Products "Crosswind" intake (Air Gap ripoff) on my car and it's the same thing. I had a Speed Demon carb also. I also ended up using a Mr. Gasket low rider air cleaner with a 2" thick element so the stock hood would shut.

Otherwise, drill and tap a hole elsewhere for your PB and hook your PCV up to the rear of the carb. IF you opt to "tee off" your PB and PCV to a common line, it's at your own risk.

CamarosRUS

I figured so for the acceleration reason but was not sure. I plan to use a 1/2" spacer and a 2" filter along with the stock ports for the vacuum stuff. I didn't feel like tapping into the manifold and planned to use the spacer anyway. I am even gaining 1/2" clearance by using the spacer and smaller filter over the stock 3" filter.

Confuzed1

iTrader: (4)

That'll work -you'll find out that you can't use a 3" thick air filter element anyway because the hood won't shut - it's that close on these thirdgens....it only gets worse.....I'm trying to find a filter now that'll tuck up under my 4" cowl and still allow my hood to shut using a blower- lol

EDIT: And make sure the air cleaner stud isn't too long BEFORE you slam the hood!! I stupidly came close to poking a hole in mine! That woulda been ugly... lol

CamarosRUS

I wish I had that problem