1958 Blow-by??

Bill Caddyshack · November 16, 2014, 11:13:29 AM

I have some blow-by through the breather/oil filler on my 1958. Oil consumption is about 1 qt every 1,200 miles. Some from small leak. No oil smoke from the exhaust. It would seem that if I was burning oil that there would be smoke. I expect that most of my loss is from the leak which I don't see the point in fixing unless it gets worse. Looks like a rear seal and a quart of oil is cheaper than a fix.

However, with winter coming and the windows up, it is getting smelly!

It would seem that the breather is supposed to breath in and the downtube is supposed to breath out. Could the downtube somehow get clogged or restricted? If so, is there some way of cleaning it?

James Landi · November 16, 2014, 12:23:04 PM

I had a '56 with the same issue... even with the ac vents mounted on the rear of the car, the noxious fumes entered the cabin at stop lights and traffic... so here's what I, Mr. Shadetree mechanic did (that will likely infuriate some of our brother and sister members).... I drilled a hole in the oil fill cap, found a plug I could pull out of the manifold, and substituted a 1/8 inch barb--- stuck on a rubber hose and fed it into the oil cap--- VOILA--- smell goes away, and all kinds of moisture accumulated on the hose. Do we lose some vacuum--- yes-- although, as I recall, my re-engineering did not seem to effect vacuum advance... but even if I lost mph, at least I was not toxifiying myself and passengers.

quadfins · November 16, 2014, 01:53:56 PM

The road draft tube really only draws when the car is moving. At a stop, blow-by gasses will be forced out equally through the draft tube or the oil filler cap, with the difference that the cap has a lititle more resistance due to the mesh filter.

My solution was to install a factory-style PCV system. I wrote an article on this some years ago, for the Self-Starter, and can send you a copy if you like. the main difficulty that you might have is in obtaining a correct fitting carb spacer with the vacuum outlet fitting. But if you are clever, you can find some way to improvise.

Jim

James Landi · November 16, 2014, 06:29:04 PM

Jim did the elegant fix... I was did the quick and dirty one... I think the results are about the same, you're removing the blow by and you're evacuating it through the intake manifold.

Ken Perry · November 16, 2014, 11:55:14 PM

When you run the PCV system,there will be less sludge in your engine. On 59s and 60s that I drive a lot,I always go with the PCV system,but the ones that only get driven a little I don't bother. I have taken apart a lot of Cad engines and the oil rings are always wore out,(BAD),down to the devider and in to it !Also most have about 3/4 inch or more of sludge in the pan. That is why they have a floating oil pick up! Ken Perry

David Greenburg · November 17, 2014, 02:55:45 AM

I installed the fix that Jim describes on my '59 several years ago. It was not difficult, and worked well. I'm not sure if the same is true for a '58, but for a '59, you can use a spacer from a '63-'66 car, which will have the nipple. I have not does this on my '60, which would be more complicated since it has the tri-power. But the engine in the '60 is in better shape and has better "breath" so I'm not as concerned.

Bill Caddyshack · November 17, 2014, 08:25:20 AM

In order not to have concern about the loss of vacuum, could I run a hose from the breather into the air cleaner on the inside of the filter - where the fumes would not go through the filter, but directly into the carb??

James Landi · November 17, 2014, 10:35:20 AM

Certainly worthy of a try... On my boat engines, there are no PVC valves, rather, there are pick-up tubes at the top of each valve covers, and blow-by enters the air cleaner on each side. I suspect the marine engine approach assumes that the noxious fumes rise with the heat and collects under the valve covers-- and there is not much blow by--- of course this approach (experiment) requires a lot of holes.... the intake vacuum is much higher in the manifold...not so in the air cleaner.

Bill Caddyshack · November 17, 2014, 11:08:18 AM

I have never given much thought to PCV valves. But this seems like the answer. Kudos to those who mentioned it earlier. Several possibilities here just need to locate a vacuum source. Not difficult and engineer one of these.

http://en.wikipedia.org/wiki/Crankcase_ventilation_system

dplotkin · November 17, 2014, 03:16:50 PM

Keep in mind that by plumbing your crankcase to your carb or intake you are masking a problem, not solving one. Excessive blow by sufficient to emit noxious fumes is caused by badly worn rings. Letting the engine ingest the excessive fumes will eventually fowl the plugs. Cars with PCV systems and excessive blow-by would become oil pumpers. Your blow by will get worse and gum up your carb. If it is bad enough to smell in the car it is probably making your oil pretty dark too. You should consider a ring job. Think of all the power you will get back.

Dan

Bill Caddyshack · November 17, 2014, 07:52:36 PM

Quote from: dplotkin on November 17, 2014, 03:16:50 PM
Keep in mind that by plumbing your crankcase to your carb or intake you are masking a problem, not solving one. Excessive blow by sufficient to emit noxious fumes is caused by badly worn rings. Letting the engine ingest the excessive fumes will eventually fowl the plugs. Cars with PCV systems and excessive blow-by would become oil pumpers. Your blow by will get worse and gum up your carb. If it is bad enough to smell in the car it is probably making your oil pretty dark too. You should consider a ring job. Think of all the power you will get back.

Dan

Dan, if the problem was really serious, wouldn't I be getting blue oil smoke from the exhaust? This is just a little smelly. Also a quart of oil every thousand miles and a few drips that probably accounts for most of it on the floor seems like no big deal to me. But I will run a compression check.

And I see no problem upgrading to a PVC. Pretty popular item.

wbdeford · November 17, 2014, 09:29:51 PM

Not necessarily--I had a totally worn out engine with all rings broken on one cylinder. No blue smoke at all. Was a '69 Dodge 318.

dplotkin · November 17, 2014, 09:43:32 PM

Bill, in and of itself adapting PCV is an upgrade that reduces air pollution and beyond elimination of a draft tube does nothing good or bad for the engine, unless it's a tired engine.

By the time an engine burns oil you can see, it is using a lot of oil. A quart in 300 or less miles. Now an engine can use oil and still show decent compression if its oil control rings are stuck, broken or tired. Some smokers still run good and that's why, usually.

But blow by is a different story. Blow by is by definition combustion gasses getting past the rings into the crank case instead of pushing down on the piston to provide power. A Cadillac or any other OHV V8 in good health will show some faint vapor at idle from the draft tube and the breathers on the engine may waft a tad, especially at hot shutdown.

PCV is fine, and it may be enough to solve your problem for years to come. If you are going to PCV, do it right. Eliminate the draft tube and install a PCV valve and hose with fittings you may have to install.

Myself, I'm a purist. I like 'em just the way they were made, warts and all.

Dan

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1958 Blow-by??