Hello everyone. My dads 1959 Cadillac has the original road draft tube set-up. I would like to convert it to a PCV system. What needs to be done to make this conversion? Do I really have to get a spacer for the carb, or can I just tap into any manifold vacuum source? I can really start to smell those fumes.. And yesterday I actually saw light smoke coming out under the car in the right lighting conditions. It has always done this, but I have not noticed it until now and I would like to make the swap.
Thanks
-Gavin
If it were my car, I'd go with the spacer.
I may still have the valley pan fitting here that replaces the road draft tube if you're interested. The spacers are available as reproductions for 63+. The only difference is they use an inline PCV valve whereas the correct 59 version screwed into a fitting on the spacer. I tried for 3 years to find one for my old 61. Eventually did but never used it. It has gone on to someone else, however.
What I did was remove the road draft tube from the section that bolts to the valley pan under the intake. I went to NAPA and located a grommet that fit the opening and then put a PCV valve in it. I ran the vacuum line to manifold vacuum. IIRC, the grommet was similar to one used in a GM (Chevy?) valve cover.
I also got tired of the fumes from my '50 but didn't want to r/r the manifold to get to the tube. I found a grommet to fit the end of the tube, got a pcv with a 90* elbow built in and ran the hose to the intake. So far it has been fine, I haven't noticed any problems. No more stink either.
T Lewis
I will be doing the same to my 59, as soon as it gets back from the damn transmission shop.
What I did with my '60 was to convert the Draft Tube to accept the PCV Valve, and plumbed the line into a T Junction in the Vacuum Booster line, and then as I was running an Electric Fuel Pump, I made up an adapter in the original Fuel Pump block-off cover to fit the filtered air from the Air Cleaner.
With these systems, one has to remove the original Oil Filler Cap and use a sealed cap, plus put a downward bend inside the air line end inside the filler tube to stop oil from going into the hose when performing an oil change.
For the Cap, and associated fitting that the cap attaches to, I happened to have an Oldsmobile filler fitting that suited the purpose.
Bruce. >:D
The oil filler cap needs to be vented. Its where the engine breaths in fresh air. That's how the 63 PCV system is set up, and continued into the late 60's.
The California 63 engines had the sealed oil filler cap. A metal tube ran from the right valve cover, up to the air breather. A filter was put inside the air cleaner, like the later model cars had. That's how the Cali motors breathed.
Russ is correct. Without an open cap, the system couldn't properly vent.
But, with the forced air intake from the PCV Valve, the factory gauze filler cap filter is being over-stretched, and the air going into the engine needs to be filtered via the air cleaner.
Using the draft tube, the only air flow is dependent on the speed of the vehicle and the air being sucked out by the venturi effect on the end of the tube.
The air that is seen when the vehicle is stopped is due to excessive ring blow by, especially on an older, usually worn-out engine.
Bruce. >:D
I wonder if the draft tubes were all the same diameter? Pontiac never changed their valley pan, they just basically removed the draft tube and had a fat grommet that fit the PCV valve. Not sure when they started but if you look up an early 70's Pontiac V8 it should be the same part.
Interesting idea to T into the brake vac line. From what I can see the brake port is basically the same as the PCV port just on the other end of the carb. I suppose only issue would be if it lowered the amount of vac available to the brakes. Guess you would have to try it and see if you can apply the brakes several times in a row without issue. I suppose the fact that normally when you are using the brakes the throttle would be closed so you get max vac it may not be an issue.
I was reading the section in a shop manual talking about the crankcase ventilation system and it said that the breater/oil caps actually catch air from the fan. I don't really see that, its not like they have a scoop on em pointed at the fan. If they did that would make some sense but basically they just have holes in the bottom of the top section of the cap so I don't see the fan making much difference. I also wonder how carefully they placed the tube under the car. I bet there are places where its a really low pressure zone and it does really draw some air but the underside of that era car has got to be pretty nasty airflow wise. I would think cruising down the highway the draft tube system would move more air than a PCV system so I would think the original breathers could handle the airflow as well with a PCV as they did with a draft tube.
It is normal to see some vapor and an occasional whiff appear from under the car at idle, especially if wind conditions are just right. Excessive smoking and odor is excessive blow-by from worn rings and/or cylinder walls which will only get worse. I tolerated that from a 62 Bonneville for a few seasons and bit the bullet with a rebuild, problem solved and an engine that makes much more power. Consider that instead of covering it up. (I understand not all of us can swing a rebuild, but eventually even a PCV hose and valve will not accommodate excessive blow-by without gumming up the valve and making the engine run poorly by screwing up the mixture).
Dan
Quote from: TJ Hopland on July 11, 2015, 11:16:41 PM
I was reading the section in a shop manual talking about the crankcase ventilation system and it said that the breater/oil caps actually catch air from the fan. I don't really see that, its not like they have a scoop on em pointed at the fan. If they did that would make some sense but basically they just have holes in the bottom of the top section of the cap so I don't see the fan making much difference.
The original cap for a 390 has it's opening in the front, facing the fan (the breather is "keyed" so it only goes on one way). The ones with holes in the bottom are not original to this vintage of Cadillac (picture attached)
Bill
Interesting. I have never seen one like that but if that is what they are supposed to look like maybe you do get some 'ram air' effect. I wonder if most of them got replaced with a more universal ones over their lifespan? Manual says they can be cleaned but maybe that was a profit item for the 'service station' to sell you?
Thank You Dan for the spacer!