I am looking for another road draft tube for my 37 to modify for a PCV system and need to know what all years look like a 37,pulled one off a 39 or 40 cab over yesterday in a local junkyard but it had holes in it after fighting it for a hour.
The COE had a normal truck road draft tube,I was expecting one longer but since the brace was not hooked up who knows. I am trying to make it look all original and hide the PCV,my plan is to insert a freeze plug in the bottom where it vents and solder a nipple to the road draft tube near where it goes into the block and then use a screw in PCV near the carb and run a hose down to the road draft tube around the rear of the engine. The tube from the COE had holes in it below where the brace was attached which seemed strange but after taking a 50 to 52 car 235 side cover off that was worse on the inside then out and the hood was shut so it must have been subjected to a bunch of moisture from the ground.
Since I have the splash pans I need a original style road draft tube so it will stick through the pan,since I have a engine on the stand now is the time to get the PCV system made where it will be easier to make.
Don't completely close off the down pipe- - - -drill a small hole just above the blockoff plate to allow condensation to drain, maybe 3/32" or so. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Don't want to get this thread to far off course. The PCV aspect caught my attention.
When PCV is added to an older engine, how do you determine which PCV valve to use? Is orientation of the valve important? Where should you connect to the intake system?
I ask these questions because of my observations of a PCV system added to an older engine. The valve is mounted horizontally and it never closes. The system is ported directly into the intake manifold. It essentially has become a big vacuum leak directly into the intake manifold. This is especially a problem at idle.
Don't want to get this thread to far off course. The PCV aspect caught my attention.
When PCV is added to an older engine, how do you determine which PCV valve to use? Is orientation of the valve important? Where should you connect to the intake system?
I ask these questions because of my observations of a PCV system added to an older engine. The valve is mounted horizontally and it never closes. The system is ported directly into the intake manifold. It essentially has become a big vacuum leak directly into the intake manifold. This is especially a problem at idle.
Link to a site most of us used to get PCV.........design, theory, testing, install plus kits
Drop by a muffler shop and scavenge up a foot or so of exhaust tubing that will be a snug fit into the hole in the crankcase. It's a pretty simple matter to fabricate a standpipe that looks almost identical to the factory part by using the upper section of the existing road draft tube and doing a little welding. If you run the vacuum line over the valve cover like the factory installation, remember it will need to be removed every time you adjust the valves. I prefer to route the line around one end or the other of the valve cover to the intake side of the engine. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
What is a full flow oil filter doing in a PCV thread????????? Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Nope, that's just an open elbow into the valve cover. It lets the air into the engine from the "clean" side of the air filter since there are no vents in the valve cover or the oil filler cap. The PCV valve is threaded into the standpipe where the road draft tube would normally go, and crankcase vapors are drawn into the intake manifold through the 1/2" steel tube that goes across the valve cover. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
"That line from the air cleaner into the valve cover" provides for a source of filtered air to be sucked down through the oil drain back holes in the head, into the crank case, out of the crankcase via the PCV valve at the stand pipe, then into the side of the intake manifold via that hard line where it gets mixed with the fuel/air mixture coming from the carburetor and subsequently burned in the process. Longest run-on sentence ever.
Carl
Last edited by 52Carl; 01/04/202010:49 PM.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
A PCV system is what's known as a "closed loop". There is no way for crankcase vapors to be vented to the atmosphere, or for unfiltered air to enter the crankcase. It was initially designed to prevent dust and other contaminants from being drawn into the engine through a vented valve cover and the crankcase ventilation also worked at idle on commercial vehicles such as delivery trucks that seldom if ever reached speeds sufficient to make the road draft tube work effectively (20-30 MPH). After the Clean Air Act of 1968 became federal law, all newly-manufactured vehicles were required to have closed loop ventilating systems to prevent crankcase vapors from being vented into the open air. California went several steps further with their regulations, and required all vehicles operated on public roads to be retro-fitted to a closed loop PCV system. When I ran a shop in central California in the 1970's, I converted hundreds of older vehicles to PCV with a state-approved parts kit so they could pass a roadside smog equipment and exhaust emission inspection. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
In the interest of accuracy, the "closed" in "closed loop" implies the presence of some type of feedback mechanism that is used to adjust the output control. For example, the O2 sensor in a closed loop fuel control system is used to provide feedback to the controller in order to adjust fuel delivery. The simple PCV systems that we are discussing here do not have any such feedback loop.
Just plain 'ol "closed" would probably be closer, but since the system draws in fresh air from the outside world is it really closed? Perhaps... At least in the context of this discussion - when comparing PCV to the older road draft tube systems.
Also, an often overlooked characteristic of the crankcase ventilation system is that under certain engine operating conditions, crankcase vapors are vented to atmosphere via the fresh air inlet. This usually occurs under certain speed/load conditions when manifold vacuum is relatively low, and the PCV valve/port is unable to mange the blow-by gasses being generated by the engine. Today's engines have less blow-by than their relatives of days gone by due to improvements in cylinder wall machining and piston ring fit - so this is probably not likely to be as big a deal as it once was.
It is very interesting that Cal. actually required the retrofit of PCV on existing vehicles! Never underestimate the power of CARB, I guess... Was PCV operation somehow verified by inspectors, or was just a visual of the installation all that was required? Did the manufacturers produce these kits? Just curious as to how they were sized to each application, and if any carburetor modifications were required when the kit was installed.
The owners of these vehicles were probably PO'd at the time, but their engines probably thanked them for less oil contamination and increased longevity.
Yes, to nitpick- - - - -you'll fit in well with the other guys here who do that, but be advised, some of them have years of experience at it. You'll have to do a lot of catching up!
About the only time vapors get vented to the outside is when the engine is so worn out that the PCV system can't handle the volume of the blowby and the air cleaner or wherever the fresh air is introduced into the system gets flooded with oil. The most common fresh air inlet during the 70's and later was a port in the side of the air cleaner housing with a small auxiliary filter installed, rather than going to the clean side of the main air filter. I've seen filter housings with 1/4 inch or more of liquid oil standing in the bottom.
The roadside smog checks were pretty comprehensive- - - -a visual check for the equipment installation, and an exhaust probe to monitor for excessive emissions at engine idle. Drivers of vehicles that didn't pass got a "fix it" ticket and the vehicle couldn't be re-licensed until compliance was proved and a followup inspection was passed. The whole idea was aimed at getting older vehicles off the road. That program didn't last long- - - - -it was just too expensive to operate hundreds of mobile test stations. The program eventually morphed into an annual inspection that was required before the license plates could be renewed. Selected shops were certified by the state as "official inspection stations". If I go into much detail about how a shop got qualified for that program, the PC Patrol will promptly rap my knuckles for getting into political commentary. Let's just say that my low budget shop couldn't afford to participate, and that had nothing to do with buying equipment!
Fun and games! Installing those kits was not very profitable, as the state put a cap on how much labor time we could charge for, but it did make for a lot of busy work, and it generated a few major repair jobs from people who had real emission problems that needed repair. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
