Opinion on PCV valve for flathead?
- Thread starter BobM
- Start date
pendeloque
New member
I have an 8BA, 1951. When I got it someone had removed the road draft tube and simply put in a pcv valve with a hose leading down below the engine (open). I did not know everything I should have, at the time. I had oil leaks around the gaskets, and oil pushed up thru the oil dip stick tube. That is what led me to understanding blow-by crankcase pressure. I then bought a simple pcv valve from NAPA attached a hose to it and connected it to the vaccuum input beneath the carb (initially for the windshield wipers, now electric). That was a few days ago. So I do not know if I have done the right thing yet. Too soon to tell. However, I have read everything on the internet about pcv oil catch cans and I am looking to install one between the pcv valve and the intake manifold hose input. Must I have a special pcv valve or is the universal one sold at NAPA OK. Is there enough vaccuum to pull thru the oil separator. I really need all the suggestions I can get. Many thanks. Peter
51 MERC-CT
Well-known member
Seeing you have elec. wipers, the old vacuum source works well.
I had the same setup until I went to a 4bbl. carb.
The PCV valve goes into the top road draft tube hole in the intake manifold. (with suitable rubber grommet etc,)
There is adequate vacuum to operate the system.
The PCV valve should be something that was meant to fit an engine close to the same c.i. displacement as our car.
Oil separators, catch cans?? Should not have to use either.
If you have oil pushing out the dip stick tube, a pcv may not have the result you want. Only stuff I've seen that did that were really really worn out, or had no breathers at all, or clogged up breathers.
To clarify, when you got it, it had a hose (where the road draft tube is ment to be) with a pcv valve in it, but this just went to air? Just flopped down the side of the engine? Could you not have just connected this to the old wiper tapping?
As above, the pcv valve should be from a comparable engine. And oil separators, not seen one used on a Flathead, though a bunch of OEM stuff had that setup. Catch cans, these are used when a PCV valve is removed on high performance stuff, the can vents to air via a filter.
Martin.
To clarify, when you got it, it had a hose (where the road draft tube is ment to be) with a pcv valve in it, but this just went to air? Just flopped down the side of the engine? Could you not have just connected this to the old wiper tapping?
As above, the pcv valve should be from a comparable engine. And oil separators, not seen one used on a Flathead, though a bunch of OEM stuff had that setup. Catch cans, these are used when a PCV valve is removed on high performance stuff, the can vents to air via a filter.
Martin.
Billseye
New member
I'm new to the group, but not new to internal combustion. Very interesting and informative post. Only point I would like to add to all of this is that on choosing a pcv valve, most have suggested using one from an equal sized engine. I would think that one should be chosen for its vacuum characteristics. Just my 2 cents...
That don't work unfortunately, though I get your thinking.
A good running stock engine, be it a tiny little import car engine or honking great a dodge hemi will have close to the same vacuum at idle and cruise. This would be around 18-22". But that hemi one will hardly work on the little'un, it would be a big air leak.
So similar sized engines are actually where you should be looking for a doner valve.
Martin.
A good running stock engine, be it a tiny little import car engine or honking great a dodge hemi will have close to the same vacuum at idle and cruise. This would be around 18-22". But that hemi one will hardly work on the little'un, it would be a big air leak.
So similar sized engines are actually where you should be looking for a doner valve.
Martin.
luvmyclassics
Senior Member
What size freeze plug is needed to block off the draft tube on a 52 8BA?
petehoovie
Well-known member
PCV4953
1949-53 FORD FLATHEAD PCV VALVE KIT
$39.95
1949-53 FORD FLATHEAD V-8 PCV VALVE KIT REPLACES THE ORIGINAL VENT TUBE WITH A MODERN "PCV" VALVE. IT WILL ELIMINATE BLOW BY SMOKE AND KEEP CONDENSATION OUT OF THE CRANKCASE.
http://jamcosuspension.com/products/sfID1/121/sfID2/80/sfID3/146/productID/1504
jrvariel48
Well-known member
This post died awhile ago, but I'm thinking of installing that exact set up on my motor so I'd like to kick it around again and get some thoughts.
Here's what I have:
1946 59L, which means I have the pan vent.
I have a Camden supercharger on a late intake and right now the road draft tube port is blocked off as is the oil fill port. I'm running an electric fuel pump so I blocked off the mechanical pump and kept the rear road draft tube set up.
From what I'm reading here, if I block off the pan vent and install a PCV set up like the one shown above, it should work fine with a filtered cap on the existing road draft tube. The hose from the PCV valve would be plumbed into the intake under the supercharger. At idle I have 21in. of vacuum and between 15 and 17 cruising light on the throttle.
Am I going in the right direction?
Thanks, Joe
Here's what I have:
1946 59L, which means I have the pan vent.
I have a Camden supercharger on a late intake and right now the road draft tube port is blocked off as is the oil fill port. I'm running an electric fuel pump so I blocked off the mechanical pump and kept the rear road draft tube set up.
From what I'm reading here, if I block off the pan vent and install a PCV set up like the one shown above, it should work fine with a filtered cap on the existing road draft tube. The hose from the PCV valve would be plumbed into the intake under the supercharger. At idle I have 21in. of vacuum and between 15 and 17 cruising light on the throttle.
Am I going in the right direction?
Thanks, Joe
51 MERC-CT
Well-known member
The PCV valve should go into the road draft port on the manifold and the filtered cap on the oil filler tube wherever it's located.
jrvariel48
Well-known member
Yes 51, that's what I'm thinking. I believe the pan vent should be closed also?
JSeery
Member Emeritus
If you use a PCV setup it needs to be a closed system except for a filtered air inlet source. So all unfiltered vents into the crankcase need to be sealed.
Yes the pan vent needs to be blocked. Not sure about the pcv hose going below the blower, these pcv chaps work with vacuum not boost.
I personally would not use a pcv on a supercharged engine. It creates a vacuum leak to the manifold and that vacuum is pulling oil vapour laden air into the engine. This lowers the octane and increases the chance of destination. Just a bad idea in my mind.
Martin.
I personally would not use a pcv on a supercharged engine. It creates a vacuum leak to the manifold and that vacuum is pulling oil vapour laden air into the engine. This lowers the octane and increases the chance of destination. Just a bad idea in my mind.
Martin.
jrvariel48
Well-known member
Thanks JSeery
jrvariel48
Well-known member
Scooder, I spoke with someone here on the Barn that runs them on their blown motors with no problems noted. I'm still listening to what you have to say. I found out that I'll be running the PCV to a port that's on the carb. It's a Holley 1850 600cfm. Will this still cause a vacuum leak problem?
I'd love to hear from the blower people if they use a PCV system or not!!
Thank you
jrvariel48
Well-known member
Will do!
Yup, still a kind of vacuum leak attached to the carb base. And still obviously oil fume laden air.
Just not something I would do.
Martin.
51 MERC-CT
Well-known member
Just wonder how millions of vehicles use PCV systems without any vacuum related issues and the "oil fume laden air" gets burnt up in the combustion process as the system was designed to do, also without any issues either real or imagined.