Kbs

Hi

need some help. I have a 371 and there is a tube that runs from the rear top of the block. Just below the intake manifold above the bell housing. The 59 engine is coupled with a 56 olds 98 auto trans.

I have no idea this is, what it does. But I notice quite a bit of smoke coming out of it when the car is at idle for a period of time..

there is no smoke from the exhaust and no extensive oil from the valve covers.

Would someone pls enlighten me on what this is and what it does?

also the engine runs to 180 degrees and after an extended period of time at idle, just quits…? After it cools a bit, fires right back up..

any ideas on this ?

any help is greatly appreciated.

OLDSter Ralph

It sounds like the "road draft tube" (crankcase breather). The tube goes down and the airstream disperses it when driving.

VC455

Unless you want to maintain all-factory appearance, some convert the road-draft tube to a PCV system. That ends the smoke and oil drips from the road-draft tube.

You would also add a breather as part of this conversion.

Kbs

Ahh that makes sense thank you. To do the conversion do I tie into the tube that runs from the valve cover (not stock) to the carb? Can you describe the conversion ?

thanks again

Tedd Thompson

When you get very much smoke from the down draft tube it is usually a sigh that you have excise blow by (pressure in the lower end) and you might check the compression for worn rings. Also this is not a sealed system so if you close off the down draft tube flow you also have to seal up the oil filler cap as the pressure will go to the least resistance and it will smoke at the top of the engine rather than under the car...Just a thought....Tedd

Kbs

Tedd

thanks that’s what I thought, odd though I get no, and I mean no smoke out of th exhaust. With the change of the valve covers and the now added pvc valve and tube to the carb adding some crankcase ventilation do you think I can just tie the down tube to that?

VC455

If some of our members with specific knowledge of a solution will read and respond to this thread, you will get the best advice.

I only recall your car with childhood eyes, so my advice will be generic.

I'll describe your objectives in more detail so that you can figure out the best way to add the PCV system.

The PCV system pulls air and oil vapor from the crankcase of the engine into the intake manifold vacuum. The second part of the conversion is to make sure you have a way for filtered outside air to enter the crankcase. This clean air replaces the oily air that is extracted by the PCV.

You could connect the crankcase end of the PCV into a grommet that you create for the road-draft tube opening into the crankcase.

Later cars connect the PCV vacuum side through a fitting on the base of the carburetor. If you don't have that option, you would need to connect the PCV vacuum into the intake plenum under the carburetor.

If there is no existing fitting that you could reuse, you would need to drill and tap a fitting into the intake plenum. In that case, you'll need to remove the intake, do the machining, and then use solvent and hot soapy water to clean out the metal chips.

For a source of filtered outside air, your car probably already has a mesh-filled breather cap on the valve cover or oil fill.

Your tube from valve cover to the air cleaner housing could serve as the breather but it must have a filter or oiled mesh somewhere in the air path to avoid pulling dirt into the crankcase.

Also consider that your engine, installed on 1961 model year Oldsmobiles sold in California, required a PCV system. You could see if those parts are reproduced. That would be your simplest option.

OLDSter Ralph

Be careful about unbolting the road draft tube. I think there is a baffle system inside the valley that will get loose. Then it will rattle around with the lifters and push rods. Check with Charlie Jones on this.

Kbs

Ok good point. Just a thought, I have a spare vacuum port that was used for the wipers, (who needs them) so I might try adding a PCV ( yea no pvc spell check this time) valve to the down tube and tie into the vacuum port. Will also check the oil cap to ensure it is vented properly.

thanks for all the help. I am looking forward to getting Dads baby back on the road.