Technical PCV Valve install question for 59ab Flathead

Can I drill and tap a hole in the block off plate on the fuel pump stand and then put a fitting in it. Then run a hose between the vacuum fitting in the intake and the fitting in the block off plate with a PCV valve in between (see yellow arrows in picture). I know the PCV valve needs to be orientated vertically and that the crankcase vent in the oil pan would need to be blocked off. Thank you

 

I’ve never done a flathead. Is there another breather at the front of the engine?
Google a V100 PCV valve; it works horizontally and in the opposite direction. Drill and tap a 3/8”pipe threaded hole anywhere in the intake under the carbs or do it to a spacer under one of the carbs. I always use a 90* fitting. The plate you show can be a spot for the hose. It’s close to the air breather and may not work. PCV valve works better if the breather, which is now an intake has a flow from the opposite end. If you picture a SBC valve on one side and breather/intake on the other. Others who have done flatheads I’m sure will tell what they have done…

 

You'll need a clean air inlet to replace what is sucked out. Normally your vented oil fill cap. Putting the PCV opening directly below that will sort of negate sucking crankcase fumes. If room to drill and tap the front of the manifold for the PCV inlet and the oil cap is your fresh air source ir would work better I think.

 

Thank you guys. I understand what you are saying. On my SBC's I always had a breather on one side and PCV valve on the opposite side and opposing ends too. It was easy to do with valve covers. Trying to do the least invasive way. Maybe I will try to make an adapter to pull from the crankcase vent on the pan. My intake does not have a blank oil tube boss up front and I was trying not to drill in to the intake runner itself.

 

I guarantee they take the “stink” away when you pull into the garage. Mine also helped the rear seal leak.. at the end at idle the vacuum on the breather should hold a piece of paper. The correct vacuum is between 1 and 3 inches and should suck from the inside of your air cleaner. Many don’t do that but the factory does..

 

PCV systems have carb (s) that are metered for the extra constant air flow the PCV provides. So if you fit one to a induction system designed for a road draft system it will work but you have just added a vacuum leak that is worse the slower the motor runs but never goes away. Some will say they done it and it works like a factory item but really?
This has been done to death over the years.
I like what you are doing but it needs to be thoroughly worked out.
Good luck with it. JW

 

I'm thinking of trying almost the exact same thing. How necessary is the vent/inlet to pull air through the block ? Isn't the pcv dealing with positive block pressure caused blow-by ? Or is there not enough air flow without a vent. Sorry sshep, not trying to hijack.

 

If you have enough air flow without a fresh air inlet vent your motor is way warn out. Pulling the air for the PCV from the road draft tube inlet would be the best improvement over the factory system. It would vent the engine the way Henry designed it, but improve the flow and burn the stink.

 

Not on a flathead but before I put my PCV system on I bought a breather/oil fill cap with a 1/2" nipple on it. I ran a hose into the bottom of the air cleaner with a fitting pointed toward the front barrels of the carb. I left the road draft tube on. The carb did suck in some of the vapors of the engine but I was always worried about gumming it up.

 

I used a 90 degree fitting at base of carb, pcv valve mounted horizontal, drawing from the valve chamber near the front of the manifold. Draft tube was blocked with a cup style core plug (odd size) in the valve chamber.
Oil filler above f/pump was changed to a cap that sealed, and I ran a tube to the air cleaner for clean air.
This set up did create a lean idle, most of which adjusted out with the mixture screws.
inside of engine was still clean after 30 years and many thousands of miles.
Have built a second system where the pcv valve is below the intake out of sight. Yet to drive this, but engine stated up ran and idled nice with two 97s,

 

I did this on my 29 roadster… check out my build project for step by step pictures and instructions… Page 76… it looks like my pictures have been somewhat lost.