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Adding PCV valve to 351W - Side Effects?
I have a 351W (Ford Crate, built by HRE) to which I would like to add a PCV valve. The engine has a dual plane manifold and a Holley 80508 750CFM carburetor. If I install a PCV valve is there anything I will need to change or adjust? Will the mixture lean out so much that I will need to rejet? Will I need to adjust the ignition timing? Anything else?
Thanks, Bob |
Bob -
I have the same engine in a SPF. I bought a breather cap that holds a PCV valve and put it in the passenger side valve cover. Per the Olthoffs, run the hose from the PCV valve to the vavuum inlet under the carburetor. Your power brake hose is probably mounted there now. Then, remove the plug from the top of the intake manifold, put in a fitting and attach the power brake hose to this new fitting. They told me NOT to put a T fitting in the line to run both to the same vacuum inlet. No other adjustments needed. Hope this helps. Steve SPF 1116 |
Re pcv valve in 351
Bob,
I have a built and stroked 351 and I did the same as Steve above said back in 1996 and have never had a problem of any kind. I drive my car on the streets and also hard at times and it has worked great. and pressure you can get out of the motor is a plus. Ron61 Ron Widener |
Ron, which stroker kit do you have? My Windsor still has a stock crank and makes a little over 400HP. 500 sounds better! Is your block modified?
Thanks, T |
PCV per Olthoffs is correct. Motor is supposed to have a PCV. However, if you've tuned carb to run without PCV, and is now getting more air with it, you may need to jet primaries up a size or two. Watch for leaning, or pinging.
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Steve.....
Thanks,
I've been meaning to do this for some time. #952 came with two breathers installed. I have the Performer RPM manifold. Any idea what fitting it may take? You saved me a call to Bob & Dennis regarding the proper hose "plumbing"! Mike |
The threaded opening into the #4 runner is for the power brakes. If manu8al brakes, leave it plugged. If power, get a brass elbow with 3/8" hose on one end, 3/8 pipe on the other.
PCV goes onto 3/8" hose at base of carb. This way, oil vapors and additional air get distributed evenly to all cylinders. You can see how getting this backwards would have all the oil vapors and extra air going only to #4 cylinder. "T" won't work either as it reduces the vacuum available to power booster by the air drawn if through the PCV. |
What is the benefit to having a PCV out of one valve cover vs. another breather?:confused: :confused: :confused:
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pcv on 351
Allen,
The PCV valve relieves pressure and if you just use a breather you can get oil fumes that will eventually make a mess on the top of the valve cover. We have a man here with a $100k plus Cobra that is now having a PCV installed because of that very thing. I know the people that built my stroker put a PCV valve in it and told me to be sure I keep it clean to take away that pressure. My big block also came from the factory with a PCV valve. Ron61 |
Ron61,
Thanks, I had to dispense with the PCV on my 351W when the Webers went on--no place to plug it into the manifold without strangling one cylinder or another. Perhaps there is another way to do it, but if it's largely a cleanliness-of-the-engine-bay issue, I can learn to live with it. |
pcv valve on 351
Allen,
You don't have to worry about the PCV valve with your webbers. If you just take the breather cap off every so often and clean it you won't even get any oil film on your motor or cover. The webbers are enough to keep tuned without trying to use this. Some of the other guys who are running webbers may be able to tell you a way to hook one up but when I had them years ago I never had one. Ron61 Ron Widener |
Somewhere around '63, or '64, PCV (positive crankcase ventilation) became standard on virtually all OEM's. Prior to that, engines had road draft tubes to vent oil vapors.
The PCV pulls a vacuum on the crankcase through one valve cover, and fresh air in through a breather the other valve cover. It allows oil vapors to burn, rather than collect inside the engine. Keeps the inside of the engine cleaner. You can run the engine without it by using another method to vent the crankcase vapors. If the Weber setup has no common plenum or vacuum source, you'll have to find something else. |
You need to have crankcase ventilation
If you don't have a PCV valve, you should have at least a road draft tube set-up.
When I first put the Webers on my Pantera many years ago, I didn't have any place to plug in the PCV valve, so I just put on two breather caps and let it go. Not long after that, I noticed my engine was building up such crankcase pressure that it would pour oil out the rear main at idle! I fashioned a road draft tube set-up, and attached it to one of the breather caps, and the problem went away. Regards, Jeff |
Re 351 pcv valve
Jeff,
When you made your road draft tube setup just how did you run it ? My 58 Ford with the 332 PI motor had a metal one that came up the back of the engine and plugged into the back of the intake but I can't remember just where. I hadn't thought about making one and running it to one of the breather caps as I now use a carb. and the pcv valve to get rid of the pressure. Your solution could cure what a guy I know is having happen and he refuses to use a pcv valve because the hose looks hokey so he has oil all over. Ron61 Ron Widener%/ %/ |
Jeff,
Pardon my confusion. Was there any vacuum on your road draft tube set-up? If not, how would that be more effective than the double breathers, and why do you think the double breathers did not relieve the crankcase pressure? :confused: :confused: :confused: |
Mine vent away from the engine and are baffled (sp) I get very little oil on the engine and I don't have to worry about the oil vapor knocking down the octane. they also make vacuum pumps for the problem you Webber guys have.
BTW: When I had a PCV plumbed through a 4150 I would build up enough pressure to push the dipstick up. I don't with just breathers. Go figure. |
I use two Chrome K&N breathers. I wipe my motor down each weekend after use anyway. If I see any oil film on my vlave covers I wipe it with a rag dampened with brake clean. I see no detriment to the motor internals as long as you are vented.
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I have a pcv valve on the valve cover and runs into the back of my Demon carb. I was pushing a slight bit of oil out of the drivers side breather. Just enough to annoy me. So I installed a remote breather and catch can. I welded on an AN fitting on the valve cover. Now it's dry as a bone. I also installed a filler cap on the passenger side.
http://www.priveye.com/dls/jazcan2.jpg http://www.priveye.com/dls/jazcan.jpg http://www.priveye.com/dls/fillers.jpg Roscoe |
Makle sure your valve cover has a decent baffle in it otherwise all that oil will get sucked up and burned in the motor instead of just dripping onto the valve cover. Two good breathers (not the fistfull of yarn shoved into a chrome mushroom) will vent all your crankcase pressure just fine, just like most circle track motors have. I really like to connect both valve covers with a metal tube that has two standoffs for the K&N type clamp on breathers.
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Thanks for all the good ideas. As a result, I purchased a second open-letter, driver-side valve cover with a baffle and tube from Cobra Automotive (203-284-3863) and will top both tubes with K&N clamp-ons. :)
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