Im glad this is the first time I looked at this thread and the last!
What a bunch of sensless hoo ha.

 

The pcv flows LOTS. So it is going to need a high volume supply. Perhaps the manifold port? Try the brakes off the opposite port at the carb. Why not leave the cross flow open, no cork, on the PB port? That way u can't have brake failure from a cork clog. The last tiny bit of cross flow can't make all that much difference, i expect.
Which carb & manifold do u have? r u using 4 hole gaskets?

 

yes i have 4 hole gaskets. i have an edelbrock performer 600 cfm carb and a edelbrock performer 2101 intake.
so youre saying i should leave the power brakes as they are and just close the pcv which runs off the primaries? see i have 2 more vacuum smaller hoses that run off of ports in the front of the carb. one for vacuum advance, and i think the other goes for interior or something like that.

 

sorry andy
i don't have your style carb to look at. so i'm only giving generic plumbing ideas.
Cars can run without a pvc valve; they did in the early 60's with big open breathers(without the breathers it may blow out oil mist, not ok). So u could test it like that, oil cap replaced w/breather. Anyway, plain cork is going to move around, as u found out, it's a bad idea.
if u post a pic or 2 of the bottom of your carb that would help.

 

Good !!!!!!!!!!!!!!!!!!

 

DANGER!!! That setup will give you drasticaly uneven A/F mix right to left. Could easily be dangerously lean on the pvc side. The PB will not be an issue. I would think you will either need an intake or combined port for the PCV. I suppose you could jet different right to left if you can plug an O2 sensor to both sides and check your mix side to side. How about sealing the primaries and running them individually and use the combined port at the rear for PB and PCV. I really think you need PCV if you want to keep oil mist out of your engine compartment or gaskets from leaking. Those valve cover breathers seem to clog up after a while then you crankcase pressurizes and the motor leaks oil. My PCV setup is a port on the oil tube at the front of the motor ( stock 1965 oil fill tube) with a sealed cap. The whole motor is sealed except for this port. The hose runs to a fitting at the rear center of the center carb with about a 1/8 inch hole in it (1963 PCV fitting). Keeps constant slight vacumn on the crankcase to relieve pressure and is basicly jetted to maintain uniform A/F mix once it is dialed in. Look at the front oil fill tube on this picture. The black hose runs from the port on the fill tube to the ported fitting at the rear base plate of the center carb (combined port). There is one port at the carb baseplate near the center port. This is for vacumn advance which doesn't affect A/F mix. If you look at the front of the rear lower carb body there is a port visible that hooks to a similar port on the front carb to equalize both ( hose is not installed yet in this photo). I have no power brakes so this is all I need.

 

andy
i found the breather i use in my old Moroso cat.
No. 68781 chrome. i bet if u ask jegs etc they sell it too, but it's not in catalog.
it gets plumbed into air cleaner base. many have a knock out plug for this. or just drill a hole in the base 1" inside of the filter. i use 5/8" heater hose to connect.
eliminates pcv valve and works MUCH better! stopped my 67 from blowing out oil with shot engine. still good 20 years later & NO rebuild and NO oil mist blowing out anymore.
.

 

Summit has it $9
MOR-68781
search under CRANKCASE EVACUATION
i've been using them since '75.
u guys don' get out much i guess

 

Ordered one today. I have a 1406 Edlebrock on a mild cam. The gas mileage is nothing to brag about. I was blaming the 4 speed and am installing a T-5 right now.

 

Welcome to the 4 hole club! Once u try 4 holes, u won't go back to 2.
.
The PCV Q was the best Q so far, so I replaced a lame Q with it.
http://community.webtv.net/MATTGRU/carb
updated 12-8-07

 

Ok. Well I fixed the problem with my rear-end and the car is back on the road. I'm gonna have to give MPG figures on the next tank. I figured out my timing issue is because I switched the vac advance from port to full vacuum. Once I switched it back to port, I can get it timed perfectly at 16/36 with no ping at all. What advantage does full manifold vacuum over port vacuum give? Cause right now I'm stuck with port unless I want to have to retard the timing to 26 deg or something.

 

The greatest percentage of blowby is made up of the products of combustion leaking past the rings, not raw air/fuel mixture. Probably 95% of what gets drawn into the intake manifold through the PCV system is the products of combustion, moisture, oil vapor and air. Remember, this is a vented system. Of these, the products of combustion and moisture can not burn and air needs fuel to react with. All in all a very lean concoction. This is why the wrong PCV valve can cause the engine to run rough. The PCV system is a calibrated vacuum leak.

BigBlockk

Later.....

 

Dude, you are accusing me of being drunk when I bring up a valid point?The PCV doesn't just evacuate blowby. If the system is properly setup it has a crankcase breather on one VC and a PCV on the other valve cover. This brings filtered outside air into your crankcase which mixes with the gasses in the crankcase and draws this in under the throttle plates, a controlled vacumn leak, and definetly not just A/F mix. On most engines this would probably cause no major harm but on a high performance street build with a dual plane, once you are off the idle circuit. you will need more fuel on that side (IE bigger jets) to keep a correct balance of A/F on both sides. If you are running higher compression, and are barely pump gas compatable this lean unbalance in A/F ratio on one side could easily put you past the safe point. Especially at cruise with only the primaries operating.
Just on the idle circuit. Once the throttle plates crack open you are still lean on the side with the controlled vacumn leak. How would you address this?

 

Good news! Low CR like 9-10:1 often likes more advance or it stalls. yours sounds great! keep us posted on the mpg.

BigBlockk
u could be right, i haven't used it in years or thought about that......
63mako-moot point....no more valve, don't care, sorry.

guys, please don't ask me about pcv or egr valves or air pumps. i don't use them. sorry

 

You beat me to it, I type slow.

 

I'm still curious what kinda effects me going from full-manifold vacuum back to ported vacuum are gonna have on things. Also, why would it ping with full manifold and not with ported?

 

now i'm confused. where was it hooked up 2 months ago?

 

It was initially hooked up ported. When I changed the spacer to the 4 hole, and started messing with the timing, I changed it to full manifold like the write-up I was following said. That's when I had to start retarding it to 26 deg total so it wouldn't ping. I switched it back to ported today and got 16/36 fine.

 

Generic tuning tips help ~80%. U r in the 20% minority. Yours likes ported. Idle is good, doesn't overheat, but gets poor mpg. Possibly the vac advance isn't working at modest cruise speeds? Test it with mityvac(min vac to start, vac in middle, vac at max, engine off); then check vac at 2500(or whatever your min cruise rpm is)-thru 3500 and write that down. Post #'s.
But this topic, is "can a 4 holer improve mpg?" So i'd rather u test the mpg 1st. Results will be more scientific.

 

Good Morning Matt your up early.