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Old 07-24-2020, 03:57 AM   #1
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Default PCV VALVE SYSTEM for 8BA with Early Intake Manifold

More and more these days, hobbyists are choosing to use a 1949 through 1953 8BA-type block for their flathead engine build. Many of the folks doing so are also opting to use an early style (prior to 1949) intake manifold on their new combination. Either of the two different iterations of manifolds will bolt-on to the newer blocks, and there are two or three good reasons that some people have decided to use an early intake on a later engine. Problem is that the two different engines were internally designed to accomplish crankcase ventilation via two DIFFERENT methods, and the design of the intake manifolds is very much involved in that process. So, the subject comes-up frequently addressing the necessity to relieve crankcase pressure with this hybrid block/intake combination, as well as the desire to evacuate at least some of the miniscule yuckleberries that are produced as a result of the internal combustion process. If many of these impurities are allowed to remain inside the crankcase and polute the oil, they usually lead to the eventual formation of sludge on the internal engine surfaces. Piston blowby produces pressures in the crankcase which if not relieved, will at the very least cause severe oil leaks at several gasket locations, and there is also the possibility of oil being blown out of the oil fill tube, not to mention the possibility that the oil pan can actually deform from internal pressure. The 'factory-stock' 8BA-type intake manifolds have provision toward the front of the manifold to mount a relatively tall tube which employs a removable BREATHER cap on top that allows an entry path for fresh air into the engine crankcase. By removing this breather cap, lubricating oil can also be poured into the crankcase. Additionally, the 8BA-type manifold has a second boss just forward of the oil fill tube to mount a 'road draft' tube. This tube serves as an exit path for crankcase vapors and pressures which build-up inside the otherwise closed crankcase as a result of the piston blowby. Below is a diagram of how a STOCK 8BA normally ventilates. So, where do we go now? 1

Eons ago, The Automakers came-up with a somewhat more-sophisticated technology for not only evacuating crankcase pressure along with sinister contaminents, but also as a method that would at least partially re-burn these crankcase gasses as a form of pollution control to save the World's atmosphere. Of course, we all know of the PCV valve by now as a precursor to more-sophisticated "smog-eradicating" systems that were yet to come. Almost every new American engine employed a PCV valve in some form by the latter part of the '60s. So, who would'a ever thunk (back then) that we might someday be seeing PCV valves on a flathead Ford engine? Well, for one thing, many 'factory' PCV valve applications have the valve mounted in a rubber-ish grommet inserted into a valve cover. Heck, any die-hard old-timer will promptly remind ya that flatheads ain't got no danged valve covers. So, what the heck here, over? What's up is that some folks a while back figured-out that a satisfactory answer to the above situation of using an early manifold on an 8BA could be accomplished by utilizing a PCV valve 'properly' plumbed and 'reasonably' engineered to restore the attributes lost when replacing the original manifold. 2

So here we are again, Heard Saxon and myself-Dick Davidson (DD), with yet another dinky idea for a contraption that will hopefully help to advance the flathead world in some small way. As I alluded-to a month or so ago, we were in the process of developing a PCV valve application for Heard's brand new, shiny 8BA with an early style Thickstun PM 7 intake manifold. Obviously, quite a few people have 'rigged', adapted...or whatever you want to call it....a PCV valve to one of these engines in the past. I never gave it much thought until Heard asked if I had any ideas on how to go about rigging-up a PCV valve to operate PROPERLY and produce the desired results. So, to have even a reasonable chance of pulling this off successfully, I decided to do a little self-education about PCV system specifics using Al Gore's World-Wide-Webb. My eyes were opened right pronto! 3

I found-out rather quickly that PCV valves work in the exact opposite fashion than I had previously believed....check the drawing/chart below! Of course, PCV valves function based on MANIFOLD vacuum produced by the engine. And you should remember that 4-cycle engines normally produce the LEAST amount of vacuum during wide-open throttle (WOT), such as during hard acceleration or 'gettin' on it'! Conversely, the HIGHEST vacuum reading will be experienced at idle, or when the vehicle is traveling on a level surface at a steady speed, and at a constant throttle setting. PCV valves usually consist of a small container with a tiny movable shuttle inside, as well as a tiny spring with varying tension values dependent upon the specific vehicle application. In general, the valve is designed such that the internal shuttle is aerodynamically shaped such that it is able to move in consideration of, and in conjunction with the airflow AND the spring's tension. My biggest mis-understanding in operation was that the valve allows the MOST flow through it as the vacuum reading is at it's lowest, as in WOT (wide-open throttle). The opposite occurs as the vacuum signal increases, like during idle.....when the internal shuttle allows the LEAST amount of flow. This really makes sense when you realize that during WOT (when vacuum is lowest, and the GREATEST flow through the valve is allowed to occur), the largest volume of blowby is being sent past the rings into the crankcase when the highest cylinder pressures are being generated. Inversely, the least cylinder pressure is being produced at idle (when the highest vacuum readings occur), meaning less blowby, and the LEAST flow through the PCV valve. 4

And concerning these PCV valves, one valve does not 'fit all'. Honestly, there's not enough 'engineer' in me to be able to determine EXACTLY what constitutes the "right choice" when it comes to making an educated decision as to which valve is correct for any particular engine. I happened to come across two different and lengthy equations that supposedly figured-into determining a correct set of parameters for the "right" valve. To me, these equations looked like the figuring that was required to set-up a space vehicle for lower Moon orbit, and return to Earth.....complicated shtuff! So, keeping in mind that these things obviously would have to operate based on the MAXIMUM vacuum value generated by the engine, as well as the POSSIBILITY that cubic inches MAY also have some bearing on all of this, I made a determination based on the facts that Heard's fine engine (built by one of our better-known FordBarn regulars in the Northeast) is 284 cubic inches and has a non-stock performance camshaft. Performance cams generally yield a lower maximum-vacuum value at idle than a stock cam does. I had already decided that we wanted to use one of those small, all-metal, early GM PCV valves with the straight through design (as seen in the pics below), both for structural rigidity reasons (we didn't want to use plastic parts), and the fact that they are sized small-enough to fit in our limited available space, plus the diameters of the two connecting points were easily adaptable to readily-available components. So, working with that 284 cu. in. figure as well as the hi-po cam, I decided to look-up the PCV valve part number used on a 1969 302 cu. in. Z-28 Chevy engine which of course, has a performance camshaft. So that's the one that we procured for this affair, and the actual part number will be shown below with all the other part numbers...........(we've already prepared your COMPLETE shopping list for you below) ! 5

It was stated on more than one occasion that MOST PCV valves will function properly ONLY when oriented or mounted vertically, or straight up and down. Most require gravity to figure into the normal operation. That really got me to thinking about how many of these valves that we've seen pictures of, or heard described as mounted horizontally underneath the intake manifold. Sounds to me like most of those are possibly not functioning correctly, if at all. Plus, when you mount one like that, you damned sure can't keep an eye on the valve, much less change it, without removing the entire intake manifold. MY opinion.....that sucks! So, I (WE) were determined (if at all possible) to rig-up a PCV valve system on this engine that made the valve accessible WITHOUT removal of the manifold, plus, any exposed parts had to be aesthetically pleasing. With that, our parameters were set. 6

And with those requirements, there aren't many options available. The idea for the most-efficient purging of the 8BA crankcase with an early intake manifold is for the fresh air to enter the breather cap on top of a custom oil-fill tube mounted in place of the stock fuel pump stand. We're going to run a remote, electric fuel pump. That air is normally drawn through the upper, rear of the valve chamber, and is drawn down into the lower crankcase. From the lower crankcase, the air is sucked-out via the removable, vertical tube that runs vertically up the front of the valve chamber. The air NORMALLY goes up into a chamber in the STOCK intake manifold and exits through the attached road draft tube that is routed outside and down below the oil pan. The air passing the open end of that road draft tube induces a suction, pulling fresh air through the entire engine crankcase chamber, relieving any built-up pressures and flushing-away the un-wanted vapors. About the only place left in our modified state to mount the PCV valve so that it will function properly, AND so that the PCV valve can be serviced without removing the manifold is to mount it inside the detachable custom oil-fill tube/spacer assembly. 7

Following is a description of our new system as applied, starting in the front of the valve chamber at the removable, vertical tube which fits tightly down into a recessed hole in the block. Heard removed that tube and cut it roughly in half, as can be judged by the picture below. The upper part will no longer be used. The lower piece will have a tapered freeze plug inserted in it's top opening. The tapered freeze plug must be drilled in it's center to accept a BULKHEAD fitting, by 3/8" COMPRESSION fitting on the opposite end. The tapered freeze plug should have the BULKHEAD fitting tightened into the freeze plug, 3/8 COMPRESSION nut pointing UP! The freeze plug should then be hammered snugly into what is now the TOP of the lower piece of the cut-off draft tube. Tap the tube/freeze plug assembly back into the designated hole in front end of valve chamber. Bend a piece of 3/8" soft copper tubing resembling the piece in the accompanying picture. Secure the inverted "U"-shaped end of copper tubing into the 3/8" compression fitting (don't forget your ferrule) mounted in the freeze plug. The remaining straight tail on the copper tubing will lie against the metal tube traversing the length of the valve chamber, secured snugly to that tube with at least two small, screw-type hose clamps. If you shape your copper tube carefully, the configuration will prevent any unlikely chance that the freeze plug would try to raise itself up and out of the big draft tube. The freeze plug is a "Dorman 555-023". The fitting through the freeze plug is described as: "Bulkhead Union 3/8 BULKHEAD COMPRESSION UNION - 18090, IMSBOLT.COM or equivqlent....about $12.00. 8

Continued Below in Post #2!


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Last edited by V8COOPMAN; 07-26-2020 at 03:05 AM.
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