The screw in FV100 was designed to work horizontally. SOME of the early PCV valves were made to work vertically and used gravity to lift the pintle off of the seat. They can hang up if used horizontally. PCV valves actually flow less air at idle when the vacuum is high and flows more air when the vacuum drops under load when it is needed more. If you mount one of the early gravity style PCVs on it's side you may end up with a rough idle due to the PCV valve not closing the big vacuum leak as it is supposed to do.
Thanks, I know one should never ***ume anything but I ***umed any screw in type PCV valve would be made to operate on its side.
If you're running a PCV & a"Breather" it is NOT a PCV system!On a PCV system the other breathing port is a tube into the air filter from usually one of the valve covers. When the car is accelerating it is NOT drawing thru the PCV valve, that is were a tube to the air filter would come in & draw fumes out of the crankcase there by positively ventilating the crankcase & that give us the "P" in PCV!lol JimV
I was brainstorming another solution, had an idea and wanted to run it by you guys that have been so kind to respond. My problem is ****ing oil because i did not build an adequate baffle, so why not reverse the airflow? What if I used the somewhat baffled already drilled coil boss hole and ran a line up to my back carb inside of the filter ring, thus giving me fresh air in. I could replace my old style breather tube with an old style capped tube with a bung and run a hose to my carb mounted PCV valve. If a baffle was needed it would be much easier to baffle the old styled capped oil fill tube then ripping out my welded in baffle and redoing it. I could very discreetly run a hose from the coil boss between the dizzy and the filtered base on the back carb. I would be reversing the airflow. If I would decide to do this the two questions I have are: would the 1/2 hose coming from my drilled port supply enough fresh air in? and do you think the old style capped oil fill would need a baffle? Maybe the ones containing a PCV bung are already baffled? Originally on the old Corvettes and such that used those threaded bung oil fill tubes did they have a baffle??
just checked my current system and with the oil fill tube vent plugged I have 7 inches of vacuum at the dipstick. When i unblock the vent and put the breather cap back on the vacuum obviously falls to zero. engine carries 15 pounds of manifold vacuum at idle
Heres how I built mine. My PCV valve was threaded on both ends and i got it because I wanted the threaded ends so I could hard pipe it instead of using rubber hoses. It was barely detectable laying down between the back carb and the distributor but I had to redesign it after I found out it would not work laying down.
So that goes back to what PnBNR said. Your current installation gives you good PVV (positive valley ventilation). To get PCV, there needs to be an intake source that pulls air through the crankcase.
The dipstick hole originates in the crankcase. Unless I am totally off my rocker, with 7 inches of vacuum at the dipstick I would say she is definitely getting to the crankcase.
A "closed" PCV is a proper PCV system.A "open" one is just something us Jamooks do on our cars!!lol.Open does vent back into the air, not into the intake! Go figure JimV
One last thing, when you thing of it a PCV is making your car run Lean!!Its actually a open va***m. JimV
actually a closed system was was a running change to the early open system. Both have PCV valves that **** the fumes out of the crankcase. They learned that some times during a heavy load there are more fumes than the PCV valve can handle and it backs up in the crankcase and came out through the open breather. The closed system came along to prevent this. When the fumes backed up into the air cleaner they were ****ed down the carb. There is nowhere near the same vacuum outside of the air filter element as there is in the intake. Normally the air enters the engine through this tube but under heavy loads the excess gets ****ed down the carb.
Well, here is what I was thinking: You have 7 inches with the vent cap plugged, and when you put the vented cap back on you have 0 vacuum at the dipstick. It goes back to 0 when you put the vented cap back on because you have restored the least resistance path and it would seem that you are now just drawing fresh air through the valley and little to none through the crankcase. I thought that the old draft tube hole vented both the valley and the lower end, which would make it more effective than a single hole through the intake into the lifter valley. BUT THERE IS A GOOD POSSIBILITY (LIKELIHOOD) THAT I AM WRONG. I'm getting ready to do a similar setup and would really like to know if there is any real difference in using an old draft tube block vs. poking a hole through the intake like you did. With the draft tube 283 block that I am planning to build its easy. But the later 60s 327 that I'm thinking of building will either require VC holes, or an installation similar to yours (or some combo thereof). Your setup is simple and will be clean once you get the baffle issue resolved. Just wondering if it is as effective as the original open systems that used the draft tube hole.
I agree it is very simple and clean that is why i did it, unfortunately i did not build a proper baffle although others here on this forum have built their baffle exactly the same and they have had no problems, that is what is frustrating to me. I am actually thinking of using the same valve in the back of the center carb but changing the airflow of my system. I will do this by sealing off my oil fill and welding a port in it to which i will hook the PCV valve. I will then go from the inside of the rear carb filter to the tapped hole in the back of the manifold. Provided the old oil tube does not **** oil and need baffling I should be in business. Filtered air in the back, dirty air out the front. If the old tube needs a baffle it will be much easier to baffle that than rip out the already welded in baffle.
Corvettes had a sealed fill tube with a pcv port in it...... http://www.ecklerscorvette.com/engine-and-related/oil-related/oil-filler-cap-and-tube.html
Look at Covette Centals web site also, seem to have better pricing and they also have the lifter valley baffle can mentioned in an earlier post for $39.00
'The PCV valve itseff is a one way valve to only stop crank case gases igniting in the event of an intake blow back and nothing to do with metering. Its a very simple system that most make complicated. This seems to be a very asked question on here and has all been answered also. JW
I think I have an adequate understanding of the system, I was more frustrated with why my baffle did not work. I thought I constructed a decent baffle and when it ****ed oil I was very surprised.
It failed due to the turbulance in the engine when running at speed and the oil being thrown from the lifters and push rods. It needs to have a much longer zig zag path to keep the oil back.If you have an old small journal baffle thats not needed,cut it open and get an idea for yours.Good luck. Cheers, JW.
Does anybody Know if the 66-67 Oil fill tube with the PCV provision is baffled from GM. I have decided to use this up front with a hose going to the PCV valve in the center carb. Just wondering if I should split it and baffle it before installing. Have you guys that are using this tube had to baffle it or not? Filtered air in will be from the rear carb (inside of the filter ring) down to my port through the coil boss. Thanks for all your responses and thoughts.
I have built hundreds of SBC and not seen one on the filler tube but it sounds like a good idea and baffling the filler tube will work well. This may help others with thier PCV issues. Cheers JW
http://macswebs.com/cddemo/66aimstub/upc**/k/files/k24a2.jpg Did that work As far as a baffle in the tube I don't know. But you'll be asking the oil to be shot straight up the tube and then defy gravity. The tube is attached at the top. Don't forget to draw filtered air into the engine. Don't forget when you go WOT there is no vacuum and the pressure will rise out of the vent, and should be drawn into the throat of the carb when the vent flow changes direction.
not to be a pain and keep this thread going, but to help others make decisions I will report on what i did today. I hooked my system up very much the way the diagram is that 31 Vicky posted. Fresh filtered air in the back, dirty air out the tube and to the center carb. I capped off the oil fill tube with a piece of steel and inserted a ****** in the very extreme end of the tube. I then connected this to the center carb, PCV valve screwed into the rear of the center carb, with a piece of clear plastic only as a test. I drove the vehicle 15 miles at cruising speed only to come home and have oil laying in the bottom of the clear hose and into the PCV valve. I will definitely be inserting a baffle in the tube. My only question is why do I appear to be drawing more vacuum than a std 66 300hp chevy would have had at the PCV valve? Should I check vacuum at the valve? Why do I need a baffle and they did not? I am most definitely sure intake manifold gaskets are sealed tight, brand new and I checked them for imprinting top and bottom when I ***embled engine.
One difference I see is the location of the pcv valve. I understand why you did it that way, but perhaps there is a valid reason that chevy put the valve at the tube with a completely different designed valve. I'm just guessing & trying to help you out.
Ya believe me I appreciate your help, everyone's help for that matter. It was my understanding the the valves were basically the same with the only difference being the flow. The one from the tube would obviously flow from the threads to the carb. You may be right, could I have too much pressure at the valve? It is ****ing that oil vapor and mist up a 6-1/2 inch tube to the center carb. Someone posted earlier in this same thread that orientation of the valve should not make any difference. I am really baffled, no pun intended.
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