Before everyone gets their panties in a wad I already checked all the tech posts and other posts on this subject but it didn't answer my question. I want run a PCV on my 8BA flathead in my 52 F-1. I'm sticking with the stock intake manifold a single 94 carb. Can I use the plugged hole near the carb base on the manifold to run the vacuum line to and will I need to put a closed cap on the oil fill tube? With removing the road draft tube can I use that hole for the PCV valve and if so what PCV valve do you recommend along with what PCV grommet? The oil pan has an Offy vent on the left side of the engine will I need to plug that as well? Any help would be appreciated! And no I don't have any pictures to post!
I've read all the teck tips also and I desided to just take a chance and see what happened. I'm running a modified 8ba in a 50 F1. I blocked all vents to the crankcase, made a plate where the fuel pump used to be, installed a PCV from a buick V6 and ran it to a manifold vacuum point at the base of my Rochester 2 jet(mounted on a Merc manifold) that vacuum line is also connects to my C-4 tranny. I've monitored the vacuum closly and found no problems. Sofar the little bugger runs and acts great!!!!
The way iv always thought a PVC system worked was like this. You want to draw fresh air in and pull the vapors out with it into the intake to be burned. There for there needs to be a way for air to get in. Plugging everything up is like expecting the breeze to blow threw your house with only one window open.
296 v8 nailed it - you need a source of fresh air. The simplest way on an 8BA is to remove the road-draft tube & use that as the PCV hole (find a grommet that fits) - then your filler/breather tube still functions as originally designed. PCV should be sized to engine, so 231 V6 Buick is pretty close. I like to size them a little small, myself, but I'm up at 7000' too!
One thing I have found is use a PCV from a engine of simular displacement. One from 327-350 Chev did not work well on my 153 Chevy II engine ,got one listed for the 153 much better. Idealy you only want one air in location ie the filler cap.
I've got a '51 8ba. All I did was remove the down draft tube and replaced with with a pcv valve. I ran a 1/4" hose from the valve to the vacuum port on the intake, just under the carb, which was originally used to the wipers. Seems to work.
I did it like this; 8-AN fitting at the manifold, 3/8 hose to Fram PCV # FV294, HELP! grommet #42052 (for some GM valve cover), you're golden! Cost me about $10 and it works great. Stock oil fill tube lets air into the valve chest.
Vac port for wipers is not optimum, I think, because it draws from only one manifold half and that has some mixture implications...PCV is a new souce of air, after all. Big port (I think it's 3/8 pipe) below and behind is perfect...it has two small passages into the two chambers of the manifold. This is the port meant for truck power brakes. It was used as the PCV port on some WWII flatheads, others used a plate under carb also plumbed to both sides. Breather in pan won't kill the system, but it is a hole in the middle of the ventilation loop. The system draws from the pan via that front vent pipe under manifold, and air has to go in, full length of valley, then full length of pan in theory. I think the PCV is a big factor in keeping innards clean and durable.
PS...not all manifolds will have the big port. And aftermarket manifolds will require some creativity.
Bruce makes a good point in what he calls the "ventilation loop". You want to have the PCV valve and the fresh air source as far apart as possible, that's why putting the PCV in the old location of the draft tube is a good idea. It means the fresh air has to flow through a lot of the engine before being sucked out the PCV, and in doing so picks up a lot of the bad vapor along the way.
I thank all you gentlemen for your input and especially ALBUQF-1 for the part numbers. My flathead runs so darn perfect right now I just don't want to screw anything up! I appreciate all the help.
I have been using the vacuum port on my 4 bolt 8cm with success for many years. I suspect the 3 bolt 8ba is the same. The manifold is factory drilled so that vacuum is drawn from both ports.
Yes, all 8BA/RT manifolds I've seen are the same as you show. I also have a big-truck manifold and it does have much larger holes. I was going to drill my holes out but it's working fine, and believe me I have plenty of blowby without the PCV!
The real reason for PCV is that the EPA did not want any fumes being expelled in to the air from an old worn out engine. I know it would be best to have such a system, but with todays oils you really don't have to worry about sludge build up. I've got a 50 Merc engine in my 39 that I built to look like kind of like an early engine. I used the early fuel pump stand and breather on a late intake and plugged the 2 front holes. After 12 years I removed the intake to reset the valves and the valve chamber looked just as clean as the day I built it. I've always meant to add the PCV but just never seem to get around to doing it.
Not sure I agree 100% with this statement (not that I have to or anything - if it works for you, no issues!) - this appears to me to be a chicken & egg issue. For the moment, I'm going to use "modern" engines - oil seems to stay cleaner longer - modern engines have PCVs. Older engines with PCVs (the very few I've converted) seem to keep their oil cleaner longer. These are relative observations - "longer" = "longer than my engines w/o PCVs" - not saying you can't keep your oil clean w/o a PCV, simply that it seems to aid keeping oil clean. Dirty oil is one of the primary contributors to sludge, along with water vapor (which is "inhaled" in a PCV system pretty early in the process) - overall, it seems PCVs help keep oil clean & prevent sludge. Not the only reason, mind, but a large contributor.
As a side note to this discussion, PCV or not, I don't think you can change your oil too much. It's cheap in the scheme of things so change often.
"The real reason for PCV is that the EPA did not want ...." In the 1930's??? During WWII? They are a MAJOR durability improver, getting out the water fumes that eventually combine into sludge and acid. Along with proper thermostats to keep temp up, they greatly improve oil quality over time and decrease any tendency to sludge or acid formation by getting out the combustion (and atmospheric) water and other fumes that dilute or create nasty combinations in there. They also provide a small incremental improvement in keeping oil on the right side of the rings. There ain't no downside. Flatheads were using factory PCV's in WWII by 1939...the idea was to keep engines in heavy trucks and bren gun carriers alive. As big an improvement in design as the filter, and a hell of a lot older than EPA. Many were used in early days in engines that had no airflow for draft tubes, stationary engines, city delivery trucks, etc. Detroit kept the road draft in light duty uses because it was cheap.
"that vacuum line is also connects to my C-4 tranny" The reason this has worked so far is because you made 2 errors in 2 different directions: 1. case shouldn't be sealed - it needs an air entry at least as large as the largest PCV opening 2. the C4 should always get full vacuum, not reduced by a leaking device Since there is no air entry, the C4 got (nearly) full vacuum and works about right. If there were an air entry, the C4 would shift late since it sees lower vacuum. Your PCV isn't flushing evil chemicals and water vapor from the case. if you decide to change it, do both changes at once: A. redirect the C4 line to full vacuum B. allow clean air to enter the case (valley, road draft, valve cover, oil filler cap, fuel pump plate) and again (as was said above) should create the longest possible path for the air to follow through the engine before exiting the PCV, which is why the inlet and PCV are frequently on opposite valve covers.
I've been running a home brew PCV valve setup on my French block flathead for over 5 years - it uses an 8BA style intake. I used the early fuel pump stand/breather/oil fill setup as already stated, plugged the old oil fill hole with a plumbing plug and used the road draft tube hole with a rubber grommet and some RTV to hold it in place for the valve. I also used a 3/8" fuel injection line hose for the pipe. Sorry for the small picture but if you click on it you can just see the connection behind the rear carb and the road draft tube area connect. BTW, I'm using 4" spacers under the carbs for a "poor mans Thickstun" setup. Besides, with the cavernous 40 Ford engine compartment the carbs now "stand out" instead of them looking "buried" in there.
A leak in the system, even a controlled leak like a PCV, reduces total vacuum everywhere in the intake. If I have 20" before I install a PCV and have 19" after, it won't matter where I measure that - it'll be 19" anywhere on the plenum. Consequently, it shouldn't matter if you take the vacuum modulator off a T junction going to the PCV or the other end of the manifold - the vacuum should be the same anywhere on the manifold.
"the vacuum should be the same anywhere on the manifold" ... in theory. In practice, it's greatly affected by the area of the common line, volume between the 2 functions, total system vacuum, distance from vacuum source to each.
Also, since PCV is an air leak and also supplies some burnable vapors...seems wise to plumb it into both sides of manifold.
Let me just ask a dumb question here,I Even having owned two flatty's I admitily don't know as much about them as most guys here so why would you want to put a pvc system on your flatty? You've stated that it runs great so why fix what ain't broke? Is it going to add power, is it going to prolong engine life etc. Arguably it will be a little cleaner for the environment but having worked in the auto emissions field for better then 15 years we all know auto emissions or the claims that they are killing the Ozone etc. are all bullshit.
Read the posts...it is not to clean the environment, it is to pull water and combustion gasses out of there. These things combine into sludge and acids. They also improve ring function a bit, like the more powerful evacuation systems on race cars. Ford put PCV's onto flatheads 70 years ago for heavy duty use. The EPA did not suggest this to them... A Positive system is a BIG mechanical improvement over the very dodgy road draft system, and if combined with thermostats (standard on flatheads since 1933) and a filter of some sort equal longer and happier engine life. Even well maintained engines developed sludge over time, and sometimes internal corrosion from acids, before PCV use moved into light duty vehicles circa '62.
I guess that all makes sense, but running as hot as Flatheads typically did I wouldn't have thought moisture would have been a concern. Then why did they wait til 62 to put them on car engines? We're putting together a 56 Fairlane convertible with a 292 Y-bock and no pcv system just the plain old road draft tube. thanks for the info just learned something new for the day now back to the old boring crap
Same routing as WWII ones, venting from above vent stack, but they thought to move valve outside then! Similar valve, weighted but not sprung, wartime one was cast and nade to disassemble for cleaning.
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