RPM Intake / PCV location?
 

running a holley 4150 carb and performer rpm intake. where is the best place to run the pcv. i don't have room under the hood for a spacer. Can running a breather to the air cleaner be a substitute for pcv?

We are using valve cover breathers on both of our cars and they work just fine; no issues whatsoever.

Just a comment:

Valve cover breathers will relieve crankcase pressure into the atmosphere, as mentioned, but will but remove corrosive crankcase fumes from the oil pan. The corrosive crankcase fumes are what destroyed the 1930s and 1940s engines well before their time.

Most people only think about not having the oil blow out of the breathers. They forget totally about the corrosive gases.

The old Road Draft Tube method of removing the corrosive gases did a fair job when the vehicle was driven at highway speeds and the Road Draft Tube was designed properly for the vehicle application.

The PCV valve system does a FAR BETTER JOB on that task, is cheap, and just requires hooking up one hose to the intake plenum, then to the pcv valve, and finally to one valve cover. As long as the other valve cover has a breather (for fresh air) on it you are good to go.

There is a TON of history on why you do this stuff for reasons other than emissions.

Just my comment on this subject.

Tom Vaught

And this is why i asked...
thanks Tom

Does anyone with an rpm intake connected to the pcv have a pic of a good way to connect? there is only 1 vac hookup and its at the back of the manifold

can the brakes and trany share vacuum?

RPM
 

I located mine in the plenum so it would pulse off of more than one cylinder.

If you can do a drilling like Shaker 455 did on his RPM Intake where you have two passages (one in each plenum) joined at the fitting you will have the most consistent vacuum signal for your PCV valve.

You can use an open spacer to do the same thing but that increases the carb height.

If you have a sealed valley pan (no PCV valve location used), you can draw from a valve cover (like I said in my post) using a rubber grommet that the pcv valve fits snugly into.

You can then attach the PCV hose to either the front of the back of the RPM intake as long as you connect both plenums of the intake to the pcv suction line.

Tom Vaught

ok thanks for the info and pic. thats what i will do.

I did go to the holley website and looked up the carb. I noticed where i usually hook up the brake boost it is labeled pcv. that couldn't be a worse location for a pontiac with a stock valley pan.

I'll be taping the intake through both plenum. Effective and clean.

"The old Road Draft Tube method of removing the corrosive gases did a fair job when the vehicle was driven at highway speeds and the Road Draft Tube was designed properly for the vehicle application."


Like the old 409s!

Tom what about using the big fitting on the back of the Holley for it and a Y for the power brakes?

dont you run the risk of leaning out one cyl, if you only plumb the PCV to one runner?

PCV setup on Torker II & evac system...
 

East coast Jim Taylor recommends running two closed breathers w/ 5/8" nipples in the v-covers, connected by 5/8" hose (I like the clear aquarium stuf so you can see if oil is migrating). Those two hoses are connected to a "T" which is then connected to a fitting mounted onto the bottom of the air cleaner. Does a great job of stopping "sweating" @ gasketed joints.

On the OP's question I run my front PCV mounted valley pan, hosed to the back of my Shaker 455 1000DP, and then run the brakes off of a 3/8" hose barb tapped into the rear of the intake.

Tom,

I have a mostly stock (4bbl, HEI, Dual Exhaust were added) 1972 Luxury LeMans with a 350 in it. In the 1972 Service manual it speaks of a "Closed P.C.V." system. The manual says the P.C.V. is located in the "push rod cover" which I assume is the "valley cover" with a rubber hose connecting it to the intake manifold and another hose (a pipe in my case) connects one rocker arm cover to the air cleaner. It makes no mention of the second rocker arm cover. You say the other rocker arm cover should be vented; are there two types, closed and open p.c.v. systems, or am I just missing a breather in my other rocker arm cover?

Thanks,
Karl

:usa2:

the breather allows air to cycle instead of just building negative pressure in the crank case

this way will reduce vacuum to the brake booster. may not be a great idea if you have low vacuum to begin with but i have seen it done without problems. the cam would be a deciding factor in this i think. but I'm no expert...

65 tripower pcv/breather question
 

I have a 65 tripower set up with pcv and a breather (not connected to intake or carb), thus no place to have carb pull gases in from the breather cap. I know the 66 tripower resolved this....but will this hurt the proper circulation of gases?

Below is a quote I found from another thread on PY talking about using an F splitter on a tripower, should I do this??:

JYD, I am running a PCV type cap on 1 valve cover and a breather on the other valve cover. The PCV goes to a "F" type splitter and 1 side goes to each plane of the Tripower dual plane intake. This is the same way a stock 66 Tripower is plumbed. I showed you my PCV type breather cap, did you not believe me? This is the same type cap that was used on Chryslers. BTW, found out why my line lock was blowing fuses and my car was idled high. The switched hot wire was loose and up against metal, it was the same circuit I used to pull in a relay for my line-lock. Clutch is adjusted and still feels strong. I may go to Silver Dollar the 19th(Saturday). It should be cool weather, 11.50's would be nice!! -Jim

I understand why a breather would be used. The question is did the factory screw up by designing a "Closed" system and I should add a vent, or did the car have a "vent" at one time and I should reinstall one, or does the "Closed P.C.V. System" work as it was intended and I should leave it alone? I do not want to just add a vent arbitrarily because as Tom's signature line states; "engineers do stuff for a reason".

:usa2:

i'll look it up

More info:

1) If you have a valley pan without a pcv connection, hook the pcv system up like a 455 SD engine. PCV valve in one valve cover that is connected to the carb. Hook up the other valve cover to the base of the air cleaner (inside the filter element).

2) If you have a valley pan with a pcv connection, hook the pcv system up like a normal Pontiac engine. PCV valve in the valley pan that is connected to the carb. Hook up the other valve cover to the base of the air cleaner (inside the filter element).

3) If you have a valley pan with a pcv connection, with a front mounted PCV valve location. hook the pcv system up like a normal Pontiac engine to the base of the carb and hook up the Power Brake booster up to a fitting tapped into the intake manifold either at the back of the intake or in one runner. The brake booster check valve traps vacuum and will work fine even with pulsations coming from just one runner of the intake.

4) Adding two "breather" lines to the valve covers does little to add more air to the crankcase as the pcv valve limits suction thru the valve to 4 cfm max. IF you have a bad crankcase blow-by issue then adding a second line allows sending more fumes to the air cleaner base but your real issue is ring seal.

5) To purge the corrosive gases from the crankcase you need an "air flow loop" that goes from one valve cover, down thru the crankcase, and then up through the pcv valve. By adding a second breather line to the air cleaner, you made it twice as hard for the PCV valve to have enough flow to pull the crankcase pressure down to a negative value. Purging the crankcase corrosive fumes is priority number 1.

With 2 lines to the valve covers the air will go from the heads into the valley area and immediately into the pcv valve with little suction on the crankcase fumes.

Tom Vaught

1 vs 2 breathers...very interesting.
Since theres very little signal at higher rpm, i use two breathers at the track.
Gon'a test it both ways at low rpm 1st chance i get.