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Thought this would pull air from the oil fill tube, through the engine, and out of the valve cover. Doesn't seem to be creating any vacuum at the oil fill neck. I blocked off the draft tube temporarily since I haven't removed it yet, but didn't make a difference in vacuum(just using my hand). Haven't done any compression checks but I'm sure the engine isn't in great health, but it isn't especially smoky under the hood with the draft tube setup either.
I'm using a pcv valve from a dodge stealth (3.0/turbo). Figured it would be big enough. The valve covers might not be creating a good seal. I tightened them a bit with no difference.
Any idea why? Should I plumb vacuum to the valley pan instead?
I would think your biggest "air leak" is going to be the oil filler tube I can see on the other side of your engine there. Nice setup though, I want to do something similar. Although I might suck from the oil filler tube instead of adding holes.
I would think your biggest "air leak" is going to be the oil filler tube I can see on the other side of your engine there. Nice setup though, I want to do something similar. Although I might suck from the oil filler tube instead of adding holes.
That's where I want the source of crank vapors to be. I'm just not seeing it there.
Originally Posted by tinman52
It would work better to put it where the road draft tube attaches. In the valve cover, without a baffle, it will just suck oil.
I figured I'd have a higher risk of sucking oil plumbing it to the draft tube location. I had planned on making a baffle if the valve cover worked.
I see what you are saying, not sure where else air would be leaking in? Do you have a vacuum gauge? Check the hose and make another plug for the oil filter to treat pressure there?
I'm interested in this solution also. I have a buddy with a "Y" block in his 55 T-bird that wants to get rid of the road draft tube.
My idea was to pull the road draft tube and replace it with a grommet and PCV valve plumbed to the carb. Now I'm not so sure if that will work. I hadn't thought about the vented oil fill cap.
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My idea was to pull the road draft tube and replace it with a grommet and PCV valve plumbed to the carb. Now I'm not so sure if that will work. I hadn't thought about the vented oil fill cap.
Bobby
That's exactly how PCV is done on flatheads. Sucking in air thru the filler cap is fine, it helps sweep out condensible vapors. On 8BA flatheads the draft tube is connected right to the crankcase, while the filler is connected to the lifter valley. Air comes in the front of the valley, sweeps along to the rear of the valley and down into the crankcase, forward to the front of the crankcase and up and out the draft tube. I'd assume they did a similar pattern on the Y-blocks.
On the Y-block, you may need to let air in BOTH valve covers, and take it out the draft tube opening. I doubt you could feel the vacuum by putting your hand over the filler cap, the PCV valve meters a controlled amount of air.
The older Y blocks has the oil filler cap as the inlet port and the road draft tube as the outlet (sucking) port.
But there are actually later models y block with a stock outletport in the rear of the valley panreally close to the vacume port on the carb plate. Barley noticeable.
Inlet is still the oil filler cap.
However I find the road draft tube outlet position (theoretically) more efficient as the inlet is in the front top and the air is sucked thru the entire motor (thru lifter gallery and down in the rear and than thru the entire crank case and out in the front.
Thats not the case with the valley cover position. Then you only vent the top half of the engine...