The Stovebolt Site Forums The Shop Area Engine Shop stupid Blowby question

O.k., please forgive my ignorance that'll be showing here, but I have a slight problem that I hope you guys can help me with some advice for.I did a search but couldn't find my exact problem. I have a '52 Chevy pickup that I bought off of a local farmer recently. The little truck was only driven around the farm for the last twenty or so years, not on the highway, until I bought it. The engine is a full pressure 235 that ,according to all the Stovebolt.com research I've done, checks out to be a '53 from a powerglide- equipped car. I noticed recently that while it pegged the original 30lb oil pressure gauge,after driving it to town (approximately 15 miles), the pressure would drop. I then noticed that there appeared to be oil all over the passenger side of the engine and it smelled of gas and was really thin, as well as being about 1/2 quart low. Dad and I diagnoised it as a bad fuel pump, so today I replaced it and changed the oil (30 weight). After driving it about 30 miles and 50 or so mph, the oil pressure dropped down to around 15lbs momentarily, then went back to 30+ lbs. I went into Walmart and shopped for a few minutes and came out to a large puddle of oil under my truck, appearing to come from the right side. Checked the oil, about half a quart or so low.I then refilled it and added Lucas oil treatment. I drove 15 miles home and the oil pressure went to dropping again. I checked the oil and it was a little low again. The truck will hold 30 lbs while idleing. Dad said that maybe the road draft tube is stopped up. The engine has no oil filter on it and has a none vented oil filler cap on it. The little engine pulls strong and idles well, and there is very little to no smoke from the truck. I plan on rebuilding, but was hoping to last this next year before doing so.I haven't done a compression check or anything on it yet, but I'm really hoping this will be something simple. If the draft tube is stopped up, how do I clean it? Thanks for all the help.

five-oh,

Without diagnosing your problem, I will say that when I was the cleanup flunky in my cousins repair shop in the dark ages, we would take nasty old fouled draft tubes off and throw them in a burn barrel.

When they came out, they were squeaky clean inside and out! Burn barrels are outlawed in my neck of the woods now, and this might have been a environmental disaster, but it sure got the draft tube clean. Good luck!

Stuart

Here is the way I cleaned mine on my 216. First I removed the attachment bolt on the pan. It had a strap that is secured with a pan bolt. Then I wiggled it free of the block. Next i took a screw driver and hammer and removed the top cap. At this point there was no visible passage between the tube from the block and the road portion. I put the assembly into a degreaser solution and several hours later it was clean. As it turned out there was a baffle inside with holes!

Unless the valve cover has vent slots in it you must have a vented cap. Check & clean the roadaft tube like the previous bolters have recomended.Check the lower part of the tappet cover. They are prone to leaking there.

The 1953 Powerglide engine is a full-pressure oil system, as you have determined. It doesn't matter if this is a '53 engine, but it either needs slots in the head cover, or a vented filler cap, as mentioned previously. I think the vented cap was original, but memory is foggy on that point. The description of the inside of the draft tube by truckernix is correct, and the tubes do get plugged. I think the parts cleaner is a better choice than the 'burn barrel', but I know the process, and it works. Heating the tube with an acetelyne torch, or a propane torch, will accomplish the same thing, if you can stand the smoke, and don't mind painting it afterword. If you use an acetelyne torch, go carefully- remember you aren't trying to melt it.

The oil pressure should remain close to 30 PSI warm, if you are certain it is a '53 PG engine. If it is the Powerglide engine, I think it also should have hydraulic lifters, if memory is correct. Maybe someone else can be more specific on that point. The occasional drop in oil pressure is cause for concern, although 15 PSI I think is sufficient to avoid engine damage unless you are running it under full load. Since you say you have 30 PSI at idle speed, that would seem to eliminate main bearings as the cause of low pressure, so the pressure relief valve in the pump might be a suspect. Having said that, I don't remember if that valve is inside the pump, or under the cover on the manifold side of the block. Foggy memory again. I'll see what I can find on that point, but I'm sure someone else will provide the answer.

Harvester

A couple of quick thoughts.

1. The first engine I rebuilt was from a 1962 1.0L Austin Healey Sprite. The second problem I ran into after I tried to get it to run was that it would spit oil filters off. The original was a cup with replaceable element. Changed it to an adapter and a screw on. Spit those off, too. Hmmmm? I probably spent at least $1000 on the rebuild, in 1973, but didn't replace the $6.00 oil pressure relief valve piston. Unlike many US systems, the piston was separate, spring loaded, and part of the engine block rather than the filter.

Oddly enough, after I replaced that piston, which was visibly scored, the oil pressure dropped down from pegging the 80 PSI meter, to about 45 PSI. Hmmmm?

Many US built oil filters have an internal pressure relief valve. Way cool unless you are serious about filtration. What I recommend is a WIX 51794 on a remote adapter. These filters are two quart with no internal pressure relief valve. They fit the same adapter as a FRAM PH-8. Change them every time you change your oil, or every 3000 miles if you are using non-synthetic oil.

2. A 1953 PG engine should keep a 30 PSI Oil Pressure Gauge pegged most of the time when the engine is off idle. It doesn't appear that is a problem for you, but the drops in pressure should be.

When I pulled the oil pan off of my 4400 with 1954 235 in it, and external factory filter, I found about a pound of crud in the bottom step of the oil pan, where the oil pump inlet is. I had trouble getting it out with a 1200 PSI power washer. Other possibilities are leaves, bird's nests, fish, etc. I'd suggest that you spend an hour or so to pull your pan and see what's in it.

The connection between the tube that runs from the pump to the strainer is also critical. If that joint comes loose, you'll be sucking air, which has little in the way of lubricating functionality.

3. Road Draft Tube. I don't think so. My 3800, which runs . . . so far, has a nasty case of blow-by. It doesn't come out the road draft tube. Maybe because it is totally clogged, but . . . the oil filler cap looks like the "Little Teapot That Could" Seriously, puff, puff puff, and it isn't water vapor or unburned fuel. You should certainly clean your road draft tube, which, as I remember the maintenance manual, is supposed to be done annually.

How many of us have been driving around in trucks where this perfectly reasonable maintenance chore has been neglected for more than 10 years?

sounds to me like its been run around the farm the last 20 yrs on the same old oil and sludge, and who knows what the farmer used to add oil when it needed it. pull the valve cover off and you'll probably find the oil drain back holes plugged or partially plugged with crud. when you get it running at higher rpm's down the highway the oil cant drain down fast enough and comes out the down tube. some of the oil drains into the lifter gallery and those holes could be plugged too, fills the lifter area up, fills the head up and theres the drop in oil pressure, nothing left in the pan. i've cleaned a couple of these that were so plugged its funny any oil returned to the pan. 1 more idea, if the oil cap isnt vented and the engine has decent blowby it will actually create so much of a draft in the downtube that it sucks the oil thats splashing around the rockers right out the down tube.

In addition to all of the above maaybe the relief valve on the oil pump may be sticking. Also try a qt. of any kind of transmission fluid to the motor oil and drive it for and hour or two. Transmisson fluid has lots of cleaners and such which will remove lots of that sludge and such. You may need to repeat this process a time or two or three. I had a late modle 94 motor with much of the same trouble and noisy lifters. This did the engine lots of good. It quited down the lifter and cleaned to inside of the motor. It did not hurt the motor and I put at least five hundread miles per treatment. Today the motor runs nice and all si quite.

A friend of mine stopped by a few years back, said he added 3 qt's of oil and still barely on the stick.....The valve cover was so plugged up the oil couldn't drain down.What a mess pulling cover and cleaning out.He still has the car but don't use it much.probbally still hasn't changed trhe oil either...

Guys, Thanks for all of the input. I've not been able to check any of these items out yet due to the cold weather-since I don't have a shop, the truck has to wait. One thing though- The only time that the oil pressure drops is after the trucks been driven at highway speeds (45 to 55 mph) It'll idle all day with the 30lb pressure gauge pegged. I think the oil pressure drop is directly related to the oil being low, since both times this happened, the engine was 1/2 a quart to a quart low when it was checked. I'm using 30w oil, do you think that's to thin? I had the valve cover off to replace the gasket due to leaking and all looks relativly clean and good there. The side pan (I forget the proper name)on the engine appears to be leaking around it. So,I'll clean the road draft tube, replace the gasket on the side pan, install a vented cap and if that don't work, I'll jump into the more complex (for me) issues. Thanks again

Maybe the drain holes from the top of the engine down through the crank case may be pluged.

I personally like Marvel Mystery Oil for cleaning internal gunk as well may be your problem. The stuff is great for this application. I bought a "Mount St. Helens" truck with oil consumption problems, 3 qts on a change @3K, and MMO brought that down to 1 qt @3k change usage. Add a qt of MMO when you change the oil and it will help a lot with dissolving the gunk inside your motor, including carbon deposits.
dg

O.K., the oil filler cap isn't vented, but the valve cover does have four 1 inch or so"vents" in it. I've burned out the road draft tube and replaced the side cover gasket, which took care of the leaks. But,after driving it again, I'm still getting a lot of oil blown out of the draft tube. Is there any certain process to cleaning the oil return drain back holes? I'm reasonably sure that the scenario of the truck being driven around on the same old oil is accurate account of its recent life. Dad suggested that it might have a collapsed ring, but if that were the case, wouldn't it be smoking? It doesn't smoke, and as I've already said, it runs great and doesn't seem to blow any oil out until it's driven at highway speeds. Sorry to bother you guys, but I'm not that knowledgable about these things. I'm willing to learn, though. Thanks

Well if you’re not burning (smoking) any and your not leaking any (an impossibility with a 216 Stovebolt) then what speeds are you trying to drive it at? When you say highway speeds visions of keeping up with the toll way traffic comes to mind, 65-70 mph. If that’s the case then your probably winding the pi$$ out of the engine and loosing it out the draft tube.

I’ve not the luxury of having a spare original untouched draft tube to do an autopsy on but it wouldn’t surprise me if it had a wire mesh to help condense the oil mist and return it back to the crankcase. This is exactly what they used to keep the oil in on the later filler caps that were used with the solid covers. After 50+ years of service such as (burn outs) and rodding with coat hangers this has probably all been burned out or pulled out allowing the oil mist at higher engine rpm to blow out of the draft tube.
Denny Graham
Sandwich, IL

Denny, thanks.When I say highway speeds, I mean 50 to 55 mph on two lane roads. I'd not take the old truck on a toll road until the T5 conversion that my friend's going to help me with later this year. It sounds plausible to me that the oil return passages might be partially plugged. I've put new gaskets on the valve cover and the side pan cover and pretty much stopped the old 235's leaks. I'll take the valve cover off this next weekend and check the return holes. The oil is definately coming out of the draft tube. I don't have a tach, but I've drove old vehicles for my entire life and I listen closly to my engine. I know that I'm not winding the little guy out too much, I'll just hold up traffic and smile and wave.