Opinions requested....

[Sharps40]

John Lee, 65 SBSS, 250 I6 (mid 70 block), 3000 miles new.

I6 manifold with only one vacuum port, below the carb, outside, center.

As ya know, been chasin some leaks....most notably rear main on this new reman engine.

Installed new felpro double lip rear main, still leaked.....found I had the PCV backwards and partly plugged breather, fixed it and the leaks essentially quit.

However, new power brakes are teed off the PCV line about 4 inches up from the manifold.

Since I only have one manifold vacuum port (noted above) and I'm concerned the total signal to the pcv is potentially less as the brake booster refills directly from the pcv line....

Bought the fittings today to create a T at the manifold vacuum source. For now will hook PCV to one side, brake booster to the other.

Opinion time:

1. Is there potential for greater signal to both systems having them plumbed at the source of manifold vacuum?

2. Does teeing the brake booster down line from the manifold source (i.e. between pcv and manifold) reduce performance of the PCV system? (especially at high speed/load and hence under conditions of reduced vacuum)

3. Both PCV, Booster and Manifold use 3/8 fittings. Does it make sense, sharging a common fitting at the manifold to restrict the port size of the nipple to the brake booster. (i.e. factory 67 had these sources separated on either side of the manifold but I need to temporarily share one port) If so, perhaps sleeving the booster niple to 1/8' diameter to smooth out signal in the pcv side as the booster refills?

[geezer#99]

Isn't there another source for manifold vacuum. My 67 had one. You can see it on the side of the intake. Square plug.
If not you could drill and tap one.

[Sharps40]

I have a 65 manifold on it....the only vacuum port is as you say, the square plugged port in the photo above.

My manifold has a boss, undrilled, for another port at the junction of the plenum and 3, 4 cylinder runners. (I believe 67 and up c10s pulled pcv and brake from these two ports, one on either side of the plenum.)

Don't want to drill it there now since it means pulling the entire intake....figured I'd wait till I have my new 2 port manifold in hand and have modified it for more direct mounting of the weber 2 barrel.

For now I'm not too worried bout trash in the booster, more concerned with maximum pcv performance. Figured if i have to temporarly share one source for brake and pcv it would be best to place the t directly at the manifold vice placing the booster tee between manifold and pcv.

I have seen some early 230/250 with a 2 port brass block on the single manifold vacuum port but not hooked up. I assume they were used to power both pcv and either booster or auto trans from a single manifold source.

[Sharps40]

Okay, no opinions. So, I'm rollin in on it tomorow or sunday. I have the lovely brass fittings to make either a T or an F. I also have a modified zerk fitting to baffel the brake port for initial testing.

[TJ's Chevy]

Originally Posted by Sharps40

Okay, no opinions. So, I'm rollin in on it tomorow or sunday. I have the lovely brass fittings to make either a T or an F. I also have a modified zerk fitting to baffel the brake port for initial testing.

Hey Rich....that intake I am sending you has dual vacuum ports...the square clogged one and one other on the middle runner....might wanna wait and see that before you do to many mods...here is a picture...maybe you'll be able to see. T.J.

[Sharps40]

Originally Posted by T.J. MCCAULEY

Hey Rich....that intake I am sending you has dual vacuum ports...the square clogged one and one other on the middle runner....might wanna wait and see that before you do to many mods...here is a picture...maybe you'll be able to see. T.J.

We'll see. That ones gonna get modded for larger plenum opening and significantly lower mountin of a DGEV 2 barrel. Just havn't decided if I'm going to turn the bowl or not. I think I'm goning to leave it bowl forward and work out a laminated adapter that short funnels into a bigger plenum opening. It makes more sense for simplified linkage and keeps the 2 barrels centered lengthwise on the log.

I'll still need two vacuum ports but breaks can tap a runner w/o leaning a cylinder....that'll leave two options for plenum location for the PCV....(PCV will burn out a cylinder if you tap it to a lone runner).

Other option is to tap the new made adapter sammich for brake leaving the PCV at the large plenum location...keeps the blow by gas more equally distributed among the 6 cylinders but would be best if it fed directly into the main barrel air flow via the 3 and 4 runner port at the valve cover side of the log. Just not sure yet if my adapter sammich will obscure access to that runner port....

Milk crate manifold engineering with beer anna file anna 20K rpm grinder. Wish I could weld, I'd make up a tube manifold like a upside down set o headers wif much smoother paths to each cylinder pair, then we'd have gravity stuffin the cylinders too!

[ChrisDollins]

Don't really have an in depth opinion, but I can look at how I did mine when I get to the office. Honestly, I didn't over think it.

Chris

[Sharps40]

Well, here it is. A thing of rare beauty. Temporary but at least its all sealed, new hoses and clamps and purtier than it were before.

[ChrisDollins]

I don't see any reason why that won't work. What made you pick that port instead of the one in the middle two runners? Didn't know if your carb was in the way, or if you think it could lean out those two cylinders? Just wondering if I should move mine.

Chris

[Sharps40]

There is no port in the middle of the runners. No provision for power brakes on 65 motors or at least not on this Baltimore Base truck...and while the manifold has the boss between 3, 4 it is not drilled/tapped....ie. this original mainfold has one port only....on the DS plenum.

It wouldn't lean out the cylinders running from the 3/4 bung because there is a separate chanel from the bung over to the plenum at the base of the carb....same as the hole/chanel that runs from the plenum to the DS external boss. Basically, if equipped with manifold vacuum ports at both locations, the would each draw from the plenum, one left and one right. Neither pulling vacuum from single runner.

[tincan1966]

In reality, it does not matter where you tee the hose. You will have the same amount of vacuum supply. All the PCV needs is enough for it to operate.

[Sharps40]

Yep. I'll wind up separatin the systems when the replacment manifold arrives. Its tapped at both bungs and I'll use them both. Should help keep trash outta the brake booster and its line and also make me feel like max capabilty is established for both systems. Course once the headers go on this fall with the new manifold, that off side will start lookin like a hose monster when I add the intake water heat. Think I'll cover all that mess with a nice fabbed up heat deflector. I think there is a water tap in the manifold side of the block so with luck, at least one hose won't have to go around and over the motor to find water.

Now on to a decent looking air cleaner. I'm thinkin 9" Specter element with filter lid in limited edition dark blue....yep, been surfin fleebay again! It'll just clear the brake booster too!

[ChrisDollins]

I went back and read your posts again but couldn't edit mine. Thought you might have meant your single port was the one in the center like mine at first. Mine is a factory 66 intake. I just assumed they were the same. That's cool to know that they run back to the plenum instead of being in those runners. I agree, wish there was a nicer neater way to plumb them. Not a fan of random hoses.

Chris