Road Draft Tube Position

[Summershandy]

I had submitted a picture where my road tube was included. Charles had mentioned that it needed to be more vertical. I don't have the same before pic but it was sitting just above a cross member and above the exhaust. I took it off and cleaned it and re-positioned. You can see it's closer to the exhaust clamp now. It actually does look better and possibly work better..... any thoughts?

 

 

Edited August 2, 2022 by Summershandy
spelling (see edit history)

[Pfeil]

Charles is right, and I prefer even more upright. I also prefer the tube to be cut at a 45-degree angle.

 

I prefer the cut to be like on this Buick below,

 The front of the car is to the left of the screen.

 

Make sure your oil filler / fill breathers scoop on the left-hand side of the engine is turned toward the engine fan to pressurize the system. It's supposed to be indexed to the pipe. The one below is off just a little, see below,

 

The reason some of these Pontiac tubes are not cut at a 45-degree angle is because they are swept back. Being swept back or cut at a 45-degree angle cause a low-pressure area on the back side of the tube that sucks out crankcase vapors. With the engine fan pushing air into the breather cap cup, the system is called the Pressure-Suction crankcase devise. The road draft tube is only a part (the suction part) of the system.

FYI, the breather filter (wire mesh) and the road draft tube filter must be cleaned every oil change with kerosene or mineral spirits and allowed to dry, then they must be filled up with motor oil and turned upside down and be allowed to drip dry of oil. Why the oil? the oil clings to the cleaned wire mesh inside and traps and cleans the air flowing through the engine.

Edited August 3, 2022 by Pfeil (see edit history)

[Summershandy]

Thanks, I made sure the oil filler cap was to spec and the road tube can't be made to much more vertical without hitting the exhaust. 

[PhilAndrews]

Nose poked down the back of my engine, this is how mine sits on the factory bracket.

Phil

[john hess]

Mark.... engine bay looks good.... draft tube is positioned like mine.... I think maybe your downpipe bracket should be attached to the bellhousing bottom instead of the frame... engine torque/twist will give problems keeping exhaust sealed at manifold and probably loosen carb also through vibration. just my observation......... John 

[Summershandy]

9 minutes ago, john hess said:

Mark.... engine bay looks good.... draft tube is positioned like mine.... I think maybe your downpipe bracket should be attached to the bellhousing bottom instead of the frame... engine torque/twist will give problems keeping exhaust sealed at manifold and probably loosen carb also through vibration. just my observation......... John 

Good observation John and valid point. Is this not the original exhaust pipe mount then? Now that you mention it, exhaust is usually mounted to the frame but with those brackets that have rubber in between the frame and the clamp. I may consider doing that now....thanks for more work! LOL

I'm actually cleaning up the car nice and purty like today for the first car show this weekend. Man do I ever miss them. Couple of them have been cancelled already and it's been 2 years since this one. I'll try to post a couple pics of it later on.

[john hess]

looks original for an automatic transmission....  just flip it over. may have to open it and flip other way also.  manual transmission bracket slightly different shape/length because of different bellhousing... I hgv ave a spare bracket and realized  it's for the automatic.. 

 

ETC reunion is sept 8 9 10.... in Ephrata PA..... still time to register.!!! pack your bags, come on down !!!!!!!

 

John 

[john hess]

there is also a small  locating bracket on one of the oil pan bolts that properly angles the draft tube... it would have a clamp around the lower part of the tube about  mid length..... I'll get some pictures tonight.    John 

[VW4X4]

Anyone consider making a PCV system for these engines.  PCV is one of the best things going.  I know it takes a way from the original condition, but there is two big advantages.  IT keep the oil cleaner, longer, along with the air.  All at not cost, other than not being original.

 

ERIC

[john hess]

downpipe bracket for automatic transmission.... like yours... 

 

draft tube bracket .... this goes under one bolt on oil pan, tab pointing up..... locates draft tube at proper angle..... gets clamped to lower part of the tube.... 

[Summershandy]

Like they say...pictures are worth a thousand words. I found it odd that the exhaust bracket was mounted right on a bend. I'll have to take a looksy and see if I can make it work off the bell housing. Kinda wish I had that draft tube bracket too. No sense making it if I don't know the proper angle. Thanks for the invite to the union.....little far for this Northerner. Enjoy!

[john hess]

not the best , but shows bracket bolted to oil pan, and clamp on draft tube.....

[john hess]

not quite sure on your automatic bellhousing,  but my standard, the downpipe bracket bolts to 3rd hole, not 2nd where I'm holding it....

[Bloo]

On 8/4/2022 at 10:22 AM, VW4X4 said:

Anyone consider making a PCV system for these engines.  PCV is one of the best things going.  I know it takes a way from the original condition, but there is two big advantages.  IT keep the oil cleaner, longer, along with the air.  All at not cost, other than not being original.

 

ERIC

 

If you are going to do that, take the following things into consideration:

 

1 ) Does the engine have real seals? It will be sucking dirt through any open hole. Positive seals on the crank, etc are a must.

 

2)  There needs to be a way in and a way out for air. You must filter the air going in (a breather cap will do).

 

3) It is far better if the inlet and outlet are far away from each other to promote better air circulation. Note "modern" systems on carbureted V8s usually have the air intake on one valve cover and the suction (PVC valve) on the other for maximum coverage. Too close isn't a dealbreaker if you can't do it, but it would be preferable if the PCV valve and breather were not right next to each other.

 

4) The vacuum port cannot be put just willy-nilly anywhere, or connected to some random existing port. If you do that it will screw the fuel distribution all up, and be worst at idle. The carburetor will have to be way rich to compensate, some cylinders will be getting washed and the car will still not run quite right. Put the PCV port directly under the carburetor, either by using a carburetor with a dedicated PCV port, or a plate under the carburetor. To work properly the crankcase air must be mixing with the air/fuel coming from the carbuetor. Right under the idle jets and transfer ports is best. Most factory systems are like this because it is the only thing that works.

 

5) It is still a vacuum leak, and there is only so much leakage you can get away with. Get a valve for an engine with similar displacement (or smaller if the engine getting PVC added is a low RPM engine). You can't have enough air to ventilate all the time. The engine wont let you have enough air to do this perfectly. Sometimes the system will blow backwards out the air intake (often a breather cap) and make a mess. That's part of the deal. In the 70s, the automakers put the breather filter inside the engine's air filter housing. That made the oil mess all over the air filter element instead of the outside of the engine. It also sucked the vapors in through the carburetor and burned them during the periods when the PCV system could not keep up. The "not keeping up" times increase as the engine ages. When the engine gets really tired, the PCV system may  never keep up.

 

6) Not all carburetors will deal with the extra air without being rejetted/recalibrated. In my experience though, it works out OK more often than you would think, but not every time.

 

To answer your question though, the only time I even really thought about it for my flathead Pontiac was on the trip home when I bought it. As it turns out, my car has a gigantic breather filter and scoop that catches air from the cooling fan. Air goes in that breather and out the draft tube constantly, even at idle. They actually brag about it in the owners manual. I have checked, and it works. I suspect it works better than PCV because my engine uses a lot of oil and I get hardly any blowback oil mess at the breather. I have seen similar looking but much smaller breather scoops on other cars that didn't seem to do much.

 

 

Edited August 5, 2022 by Bloo (see edit history)

[Summershandy]

Like this sir? Sure felt like it belonged there. I was going to say I'm inclined to make a bracket for the tube seeing how it can bounce around. You since posted your pic so back to the garage I go!

 

[Pfeil]

8 hours ago, VW4X4 said:

Anyone consider making a PCV system for these engines.  PCV is one of the best things going.  I know it takes a way from the original condition, but there is two big advantages.  IT keep the oil cleaner, longer, along with the air.  All at not cost, other than not being original.

 

ERIC

If the road draft system is maintained like I outlined in my thread above, the oil will be just as clean. If you change to a PCV system, the redirected harmful crankcase vapors consisting of water, acids, sulfur will now be ingested by your engine which effect carburetor mixture and leave nasty deposits on the back of your valves. 

 

 If the vehicle was converted, it would probably be Type 1 or the open type of system that was used on cars from 1961-1967 which take in fresh air from the breathers which flow around the crankcase and lifter/pushrod or valve spring valve stem area of a flathead to the PVC valve to intake manifold to be burned.

Type 2 systems are a closed system which would consist of a small intake filter located inside the air cleaner to a hose to the valve cover where the air circulates thru ought the crankcase and a PVC valve and hose to the intake manifold.

 

 

NOTE: When a type 1 or type 2 system were added by the factory when new, the factory recalibrated the mixture for the idle circuit and the cruise circuits. Type2>  

Edited August 5, 2022 by Pfeil (see edit history)

[PhilAndrews]

If your rings are halfway decent the road draft system is fine.

Plus, there's no harm in a slight oil haze under the car- you can see where it's protected the sheet metal on mine over the years!

 

I had a '65 Hillman which had a similar road draft system and hot, in traffic people would roll their windows down and tell me my car was smoking underneath; this one doesn't do that even when hot so it stays - I've not had any trouble with the oil since I've been driving the car really. (Have run both straight 30W and 15W40, both behave very similarly).

 

The bracket angle isn't critical- mine doesn't quite match but clamps down securely. Just prevents any unwanted torque on the valve chest cover, to prevent it from cracking over time.

 

Phil

[PhilAndrews]

...plus, thinking about it, if you change that to a PCV you run the risk of potentially starving the valves of lubrication. They rely heavily on the oil getting hot and misting in the lifter chest, that being drawn up through from the crank case. 

[Summershandy]

More on the lines of John's set up and thanks for making me aware of these brackets. I would have certainly been upset if my draft tube fell off somewhere!

 

[PhilAndrews]

The factory one is a touch more substantial but that's better than not having it.

I would clamp it closer to the top and just trim off the excess, that may just serve to buzz and rattle.