The Stovebolt Site Forums The Shop Area Engine Shop 53 Chevy 3/4 ton

Not sure if the engine size but very recently it began blowing oil out of a PCV valve in the front of the valve cover, I see 76 GM on the block there are # ‘s but they appear to be serial #’s.
I I tried to post a picture but it says the size is too large.

What exactly is your question?
The screen that says your photo is too large should give you the option to resize it.

I don’t see how to reduce the size of the photograph.
First I’m trying to figure out why it’s blowing oil residue from the valve cover PCV valve. When I first drove today my cab filled with smoke like oil. After I drove a while it stopped doing that.

3/4 ton not 2/4!

In the upper left of your picture there is part of what looks like a date code. There should be one or two more characters to the left and another thing further left that looks like the screw head to the right of the "5" shown.

If indeed it is a ‘70s 250 I-6 put EVERYTHING back exactly as it was delivered from the factory. Make sure everything that is supposed to be open is open and everything that is supposed to be closed is closed. All filters in place all valves in place. If it still blows oil you are looking at a worn out engine.

As Buoymaker pointed out, you basically posted this same question before. Posting the same question multiple times hoping for a different response is not good forum etiquette.

One picture shows something like an oil pressure or temperature probe without a wire hooked to it, recognize what it is?

Pictures of my engine with a PCV valve placed in the front hole in the valve cover. This is the one that was blowing oil mist out.
The pvc in the back goes to the carburetor.
The intake manifold is from a Ford as well as the carburetor. The engine backfires when I let off the gas to slow down. I can’t adjust the carburetor when it’s hot (can’t reach the screws).

I apologize if I’m wasting someone’s time or confusion but something changed a few weeks ago. It has not blown oil out in years since I put a PCV in the front. A few weeks ago the front PCV blew out while I was driving. I replaced it but now it was blowing oil out the front pvc hose. After driving about 15 minutes it stopped blowing out.
Now the starter is not starting / turning smoothly sort of like grinding. Guess I’ll remove the starter & have it checked out.
Yes, looking for advice on anything that I can understand!
Thanks

That looks more like a Clifford aftermarket manifold to me.

Maybe this will help explain it.
http://oldcarmanualproject.com/manuals/GMC/1979/LTService/06E/pages/79GMCService0701_jpg.htm

Get the numbers/letters stamped into the block behind the distributor and post them here. It may help ID your engine.

Oh. I see we already tried that: https://www.stovebolt.com/ubbthread...ing-which-engine-i-have.html#Post1402666

Ford intake manifolds don't fit on GM engines. Yes it could be a Ford or Holley carb but the intake is some aftermarket with an adaptor plate for the carb.
The front PCV valve is doing nothing as it isn't connected to anything. Since you have an aftermarket air cleaner you could plug off the
forward hole and install a breather cap to replace the oil fil cap. As indicated previously, the engine must be able to breathe or it will
throw oil out wherever it can.
It does sound as if you may have a worn engine causing excessive blow by.
Fred

Yes mine had that when I bought it 13-15 years ago. It blew oil through the mesh making a mess.
It’s been doing good until a month or so back when I realized that it blew the front PCV out. Since then I replaced the valve as done previously. Now as the engine warms up at 45 mph the cabin fills with oil smoke. After a 20 minute drive it stops smoking much.
I’ll look at my air filter looking for a place to put that hose.
Thanks

Hi Fred, as stated I may have a worn out engine? I like to understand things so what is worn out that would cause blow by.
Worn out rings? I need to do a compression test?

Glenn,

A number of folks have provided you some good replies and info on things that you need to and should do to correct the PCV set-up you are currently running. The set-up as shown in your pictures is contrary to how it was designed and will continue to cause you oil mess and smoke issues by itself until you take steps to correct the issues.

It also appears from your descriptions of the conditions that yes, you may very well have a worn out engine issue. Typically when you get excessive oil smoke (and even oil spewing out) coming from the valve cover and attached devices/hoses, it is a very good sign that your rings are severely worn. Oil smoke and spray could also be caused by severe valve cover gasket leaks. Suggest you should also investigate this to make sure that is not the cause of your problem.

As to your question "I need to do a compression test?", my answer would be "yes" based on what has already been described/encountered.

While you digest this info, and consider what your next steps may be, we will await your replies and see what further can be done to help you solve this problem.

Good luck.

Thank you so much! I’ll be working on it, slow as it may be!

Good evening friends. I did ID my engine size, it is a 292 strait 6. I replaced the starter this afternoon, it now spins over and fires up so fast, after I adjusted the choke on the carburetor. I didn't know how to do that but saw it on a you tube.
F/U from my previous post, I bought a vacuum gauge but I don't know where to put the hose. I placed it in the rear of the valve cover where the PCV that goes to the carb is.
The gauge did not read anything but when I removed it from the valve cover hole the engine stopped.
I also put the hose located at the front of the valve cover into the breather. That is the one I saw oil residue blowing out of. (that might help). Also the engine is idling well it is not steady (it slows down and speeds up some regularly. There is also a vacuum port coming from what I think is the choke spring. I put my finger of the opening and there is vacuum but does not seem to affect the motor idle.
I changed the oil and filter. Next I want to check the cylinder compressions.From there I should be a able to determine why and where the oil is blowing out from.
Any advice is welcome.

If you still have vacuum wipers, the easiest place to hook the vacuum gauge is to the port on the intake manifold that supplies vacuum to the wipers.

The erratic idle (Slow down and speed up) indicates that a carburetor rebuild is likely in order. The needle and seat probably isn't doing its job.

Hmm, it had them but I replaced with electric ones. Maybe the hose is still under the dash! That could be related to the idling irregular.
This is a relatively new carburetor. Maybe it’s related to a vacuum leak. I.E. the replaced vacuum wiper motor ?
Wondering where that hose goes to?

At it today. I found the carburetor bolts at the intake were pretty loose.
The valve cover bolts were loose.
I’m posting a picture of part of the carburetor choke I believe it is. There is an open port there with a vacuum there. I don’t know what to do with that??
I am looking for a place to connect my vacuum gauge…
Also I can’t locate the old windshield wiper vacuum hose???
I appreciate the help!

Maybe the vacuum wiper hose is supposed to be connected to the vacuum port you just discovered? The choke doesn't have vacuum lines. The choke might have a heat riser tube from the exhaust going to it to operate the spring which works the choke valve.

If it actually has suction (vacuum) then it needs to be plugged. Take out the brass fitting and go to Ace Hardware. They'll have a brass plug with the correct threads. If they don't, they'll at least have a brass nipple, over which you can install a rubber vacuum plug.

You can probably connect your vac gauge to it if necessary.

There is a vacuum line going to the choke mechanism, I used that to check the vacuum. It was steady and at about 22 MM. I drove it for about 25 minutes today, still smoked at speeds above 45 with fumes inside of the cabin coming from the (now line running into the breather). It seems to stop smoking as I previously said after driving about 20 minutes.
I can tell it runs better, cranks up quickly, I set the carburetor and idle speed before I left to drive. After it warmed up to operating temps it would idle too fast. I idled it down after getting home and plan to let her cool off and crank up again and see how it does.
It used to backfire like inside of the manifold when I would let off of the gas at 45 MPH, now it hardly does that.
I need to check the compressions but maybe tomorrow, I am just too tired now.

I'm confused. Is that brass threaded fitting in your picture an open vacuum port? Does it suck air while running?

After driving, now home and cooled off some, I see oil over the right side of the engine appears to have come from the PCV valve on the front of the valve cover. But now I see that I overfilled the oil, well above the full line.

glenn,

After looking at your latest picture and reading the whole thread over, really need to know what carburetor you have installed??? It is clearly not an original for the 292 nor does it match original equipment that came with your '53.

Please find and report all identification info from your existing carburetor (brand, model, tag or ID number if present) to help us know what you have to better offer suggestions.

In reviewing your picture, I see 2 possible problems that relate to vacuum and or vacuum leaks which will affect your engine operation significantly.

I grabbed your picture and added some arrows (attached below) to point out 2 possible vacuum related issues that seem to need attention.

The larger arrow pointing left seems to be your mentioned unused port that has vacuum when the engine is running. As that appears to be part of the electric choke mechanism on the carburetor, an initial guess would be that it has to do with a vacuum operation of the choke mechanism (someone with more experience will hopefully chime in to make this clearer).

The smaller vertical arrow is there to point out what appears to be an intake manifold vacuum port (looks uncapped/unconnected to anything). Can only surmise that at one point it may have been used to provide vacuum to the former original vacuum wiper system or was maybe part of the original 292 carburetor choke controls (only guesses).

With both of these apparent vacuum leak sources, your engine will run erratically with poor performance at best.

It could be possible to use the 2nd identified port in the intake manifold as your vacuum gauge connection, which would solve at least one of your vacuum leaks.

Can't really provide more help on the 1st open "threaded" port until we know for sure what carburetor you have as its designed function needs to be known.

One other note related to this picture - your electric operated choke mechanism appears to be disconnected (nothing connected to visible electric terminal) so no idea how your choke is supposed to work with out that being connected.

Hopefully this is useful info for you to chew on and you will report back so we can try and help you further.

Dan

Thank you O, that threaded port does have a slight vacuum at it but just enough that I can feel it. With it running I can plug it then release it with no noticeable change to the engine.
I’ll take better pictures tomorrow & explain what I have better.
Also try to ID the carburetor itself. Probably a cheap off brand but it is identical to the one that was on it when I bought the truck about 15 years ago. I replaced it about 2 years ago.

Cap or plug the fitting in your photo. It's supposed to be pulling air through an insulated metal tube that draws hot air from around the outside of the exhaust manifold to help release the choke as the engine warms (called a "choke stove"). There's also an electrical heater on the choke cover that could be connected to ignition switch voltage through an oil pressure sensing switch. Whatever that Mickey Mouse carb is, it has NO provision for choke heating. The carburetor will run terribly rich until the under hood temperature gets high enough to release the choke a little. Try posting a wider angle photo of the carb. It appears to be a relatively new offshore knockoff of a generic "one size fits none" carburetor.
Jerry

Yes Dan, plenty to look for tomorrow.
I’ll look tomorrow but I think that unplugged port was connected to a short hose going to that brassy colored unit is a diaphramitic vacuum for moving the choke. I used it to check the vacuum today.
Not sure if I posted that picture so here goes.

Both of those observations make sense! I’ll look at them tomorrow!
Not sure if I posted but I did a vacuum test today using the suction from the diaphragm on the carburetor.

Afternoon. I was able to take some pictures & connect a wire to the electric choke, then remove enough oil.
I’ll be looking for advice on adjusting that choke, I’ve never done this one but I’ve done old VW if they’re similar.
I’ll be looking for a hot wire to connect the choke.
You will see a picture of a screw next to that vacuum that needs a heat source or to be plugged off.
The 5th picture was to verify the intake for anyone interested. But I would like to know what the plug is screwed into the head. Looks like a heat sensor it's never been used by me.

The wire to the electric choke should be connected to the ignition switch circuit so that it comes on when the key is turned on.

My '76 F-150 has an electric choke. Before starting, I turn the key to "On" for a few seconds to allow the choke to move into the proper position, then I start the engine.

You can turn the key to ON and watch the choke valve move into the correct position for cold starting.

Yes O, I understand that but the mechanism, butterfly should be positioned correctly before starting the engine and normally the valve opens fully after warm. I know the butterfly valve stays almost closed all during my driving. If I open it manually the engine would choke down.

The electric heater RELEASES the choke, and voltage should only be supplied to it while the engine is running. I use an oil pressure sensing switch to accomplish that chore. If the engine happens to stall during warmup, the choke stops being heated until the engine is restarted.

Adjust the choke cover to just barely close the flap valve at room temperature, and adjust the fast idle screw to open the throttle a little and increase RPM once the engine fires. Cold start procedure: Tap the gas pedal ONCE to allow the choke to close, and crank the engine until the engine starts WITHOUT TOUCHING THE GAS PEDAL. The engine will get the proper amount of choke and assume the proper warmup speed with no input from the driver. You can adjust the fast idle speed if necessary to avoid stalling or over-revving once the cold engine starts. Once it's warmed up, tap the throttle ONCE to allow the engine to assume the correct hot curb idle. A properly set up and adjusted automatic choke is idiot-proof when it's used properly. During normal hot engine running, the choke flap should be completely vertical and provide NO restriction. If the engine stalls with the choke fully open, raise the idle speed with the adjusting screw at the base of the carburetor.
Jerry

Afternoon. I was able to take some pictures & connect a wire to the electric choke, then remove enough oil.
I’ll be looking for advice on adjusting that choke, I’ve never done this one but I’ve done old VW if they’re similar.
I’ll be looking for a hot wire to connect the choke.
You will see a picture of a screw next to that vacuum that needs a heat source or to be plugged off.

I believe the flap valve should move open/close as I turn the adjuster. As it sets now the flap does not move as I turn the adjuster.
Hopefully the weather will permit me to work on it tomorrow. Picture # 2 from the left shows a screw, that is what I previously turned thinking I was adjusting the choke. Would you know what that is?

Thank you Dan, I posted more pictures on page 4. There are no names on the carb. Hopefully the weather will allow me to work on it tomorrow. Thank you!

Automatic chokes are smarter than all drivers (and most mechanics). The flap at the top of the air horn will close as the plastic cover is turned IF THE THROTTLE IS HELD OPEN SLIGHTLY AS YOU TURN THE HOUSING. It will not move anything if the linkage is being held by the curb idle screw. Always do the initial adjustment to close the flap with the throttle held open a little bit. Once that setting is done, then you can proceed with the fast idle adjustments and other settings.
Jerry

Make sure the guts are still inside the plastic cover on the choke assembly.

glenn,

Just a follow-up note to my previous reply with your picture that I added "2" red arrows too.

I don't see in any of your replies after my reply that says you investigated the possible open vacuum connection in the intake manifold that has the vertical red arrow pointing at it (located below and slightly to the front of your carb mounting on the manifold).

Did you check that? If it is in fact a vacuum port and still open, it will affect how your engine runs.

Dan