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PCV/Crankcase breather options for Blown big block

9K views 9 replies 6 participants last post by  bentwings 
#1 ·
Hey guys! I know this topic has been covered before other places but I keep seeing posts that sway back and forth on this subject.

Basically I have a roots blown 454 and am close to firing it up (just finished the ignition and fuel lines, just need to do some wiring) and am unsure of which way would be the "best" method to run a PCV/Breather setup on this. Few things first
  • It'll be a street/strip car
  • I dont want the blowby/oil to recirculate back into the motor
  • I dont want a messy engine bay as I've heard people say happens with 2 breathers
  • Not in the market at the moment now for a vacuum pump for oil/blowby
  • I dont want to "modify" my valve covers (cutting, ect)

So my plan was I found these Earls push in PCV breathers that come with -6AN hose connections, and while they are pricey they are the right size for my valve covers (which are baffled also) and have a -6AN fitting I'd use. Now my original plan was to use two of those PCV breathers and run them both to a twin inlet breather tank Like this one here.

Or another option I was reading was to use one valve cover with the PCV breather to a breather tank and just using a regular breather on the other valve cover.

Anyone have inputs on which of those methods would work "the best"? I understand the PCV function and such but as this is my first blown street/strip motor I didnt know if there was any route like those two that was better. Thanks!
 
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#2 ·
What you are describing is running a breather system with no PCV. I'm not a fan of no PCV for a street driven car due to the crankcase never has a vacuum put on it. This leads to a leaky motor. For a mostly exclusive strip motor - no problem.

I seen you mentioned you don't want to run either a PCV or a vacuum pump - why not?
 
#8 · (Edited)
I'm not starting a p'ing match here, but I'd not use that engine builder again if he advised you of that if your motor was going to be used for a street application. But if your motor was built as a race motor, then I'd agree with your builder because the bulk of the use is at WOT.

Using a PCV system doesn't mean you're going to be running oil in your cylinders, but rather oil vapor, and a small amount of it as well. If your PCV system is supplying enough oil into the cylinders to cause plug fouling or detonation, then your motor has larger issues than the PCV you installed.
 
#5 ·
I've done that on old school performance motor cycles, ran the line into the exhaust :thumbup:

Don't know what your expecting but I'm on my 10th Supercharged Performance Vehicle and there's no reason not to use a good PCV Valve on one side and an open vent on the other side. With a sound motor unless your running really high boost you shouldn't see a single drop of oil coming out of that vent.

My old Sierra Motor after 3 or 4 years of me beating the piss out of it
Fully Built Fully Forged Solid Roller 502 with a 871 & Twin 750 Holleys

(hell I never even cleaned the Breather in all the years I owned it)
 
#6 ·
Thanks for the advice guys, as always its really appreciated.

Regarding 64nailhead on your vacuum/pcv question I dont really have the extra cash for having a vacuum pump and as for the PCV I just dont want crap getting into my mixture, but like my chevy head coworker I talked to at work, he says I'm overthinking it, which I probably am. My valve covers are baffled, and like I mentioned it'll be a street/strip car, so youre right in which I shouldnt see any oil going in but again its probably me overthinking/being paranoid

If I were to run a breather on one side and a breather tank on the other like you guys mentioned vacuum was my one concern, but I think I will run a breather on one side and run the other to the PCV on one of my carburetors.

I guess another option I have is a breather on one side, and a PCV valve on the other going to a separator tank then to the carburetor so I still have vacuum but a separator tank just in case.
 
#9 ·
Thanks for the advice guys, as always its really appreciated.

Regarding 64nailhead on your vacuum/pcv question I dont really have the extra cash for having a vacuum pump and as for the PCV I just dont want crap getting into my mixture, but like my chevy head coworker I talked to at work, he says I'm overthinking it, which I probably am. My valve covers are baffled, and like I mentioned it'll be a street/strip car, so youre right in which I shouldnt see any oil going in but again its probably me overthinking/being paranoidCORRECT

If I were to run a breather on one side and a breather tank on the other like you guys mentioned vacuum was my one concern, but I think I will run a breather on one side and run the other to the PCV on one of my carburetors.

I guess another option I have is a breather on one side, and a PCV valve on the other going to a separator tank then to the carburetor so I still have vacuum but a separator tank just in case.
I run the PCV into the intake and with boost put a check valve into the line to keep from blowing boost into the valve cover similarly to where the check valve would be placed for the brake booster.

Regarding the vacuum pump - you can spend piles of money on one and I agree that the price of them stinks. I took an air pump from a late 90's GM V6 that was designed to pump air into the exhaust, reversed it and hooked it to the the same catch can that you are using. I'm running EFI with an aftermarket ECM that turns it on when the vacuum/boost are at zero and then it stays on for 3 seconds after dropping out of boost. I've got less than $50 tied up in piping, pump and relay. I'll look for some pictures. There is also a Ford pump that was a stock piece on a certain year Mustang, but they are hard to find at a JY and are about a $100 to buy new.

But the same can be done with a Hobbs switch. I should mention that I'm using it on a turbo application which does work differently than a blower. If I were you I'd see how ProStreetRob has his hooked up.

In the picture you can see the hose that heads off to the fender - it's hooked to the pump that is under the inner fender in front of the right tire. I had some better pictures that were on a different computer that crapped out :( and this picture is from a quite a while ago - we moved some stuff since then, but the vacuum pump system is still the same.

Almost forgot - this motor with the turbo has about 11000 miles on it of 'spirited' driving with no leaking seals.
 

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#10 ·
I don't see any reason not to use a PCV system. It's easy. My aluminum valve covers have provision for a breather on one side and a rubber grommet on the other for the PCV valve. Then you simply use a port on the carbs meant for it. With the carbs on top of the blower they will see vacuum all the time, even at full throttle. There is no need to plumb the line into the manifold then try to deal with boost.

I've got over 20k miles on my Willys with a PCV system like this. It essentially works just like a stock one. I get no mess from blow by.

Race car only then just use a pair of breathers on each side.

I think the race rules require supercharged motors to use a catch can attached to the valve covers instead. You will need it if you burn Pistons!
 
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