Engine Smoking Opinions

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
dlevy
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Engine Smoking Opinions

Post by dlevy » Fri May 25, 2018 6:14 pm

Hi,

Looking for some realistic opinions on an M38A1 F134 engine that is smoking.

Newly rebuilt engine.
Runs smoothly
Appropriate power when driving
Greyish exhaust smoke within a couple of minutes of starting.
When letting off the gas it puts out a bigger puff of smoke.

The anti-freeze level stays constant
Cylinder compression is within 10psi in all cylinders
The o-ring seals are on each of the valve guides (took it apart to check)
The PCV line seems clear of oil

Spark plugs DO have a black oily appearance

Thanks,
Dave
Last edited by dlevy on Sat Jun 09, 2018 6:54 pm, edited 1 time in total.


KiwiMB
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Re: Engine Smoking Opinions

Post by KiwiMB » Sun May 27, 2018 11:29 pm

Hi Dave,
I note you say "newly rebuilt engine". So I'm going to make some assumptions here:
Rebored cylinders, new pistons and rings with the rings installed correctly! Inlet valves & guides replaced and as you say, valve stem seals in place.

My question for you is how much idling did the engine do when you 1st fired her up? The 1st few minutes of start up are critical for rebuilt engines and in particular for the rings to bed in. If the engine did more than (say) 10 minutes idling you COULD have glazed rings and or cylinder walls. Take your Jeep for a good long run, and preferably take her up a few big hills (get your foot hard on the gas pedal!). This increases the cylinder firing pressure and temperature which should help in bedding the rings and getting the smoke under control.

If all the spark plugs are showing the same oily appearance it suggests something common across all cylinders so start with the good hard run.

Reality is that piston rings bed in, in the first few moments of start up so being gentle on your new engine by "running it in" is a thing of the past.

Cheers

Ian
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1953 M38A1 Nekaf
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Re: Engine Smoking Opinions

Post by dpcd67 » Mon May 28, 2018 5:56 am

Look in the engine TM and it shows the break in procedures; most of us don't have the dynamometer machine to simulate the loads, but I do that on the road. It does start out with no load and it is about a two hour procedure.
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Re: Engine Smoking Opinions

Post by Joe Gopan » Mon May 28, 2018 8:48 am

Could be the Intake Valve"O"-Rings are installed wrong.
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Re: Engine Smoking Opinions

Post by dpcd67 » Mon May 28, 2018 7:11 pm

Do you really have an L134? In your A1?
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Re: Engine Smoking Opinions

Post by Joe Gopan » Tue May 29, 2018 3:21 am

Only 4 Cyl. Jeep valves that have O-Rings are on the Intake Valves of the F-134, and if not installed correctly, the engine will suck oil past the Intake Valves and smoke. The "O" Rings do not go on the Guides, check your F-Head engine manual.
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Re: Engine Smoking Opinions

Post by dlevy » Sat Jun 09, 2018 6:58 pm

This is the wrong place for the o-ring valve guide seal, isn't it?

(I meant F134, my mistake...)

Dave
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Re: Engine Smoking Opinions

Post by Joe Gopan » Sun Jun 10, 2018 3:50 am

That is incorrect and is not doing anything, it cant help but smoke. While you are at it, check to see that the tight coils of the Intake valves are contacting the cylinder head. Get out your TM. And those "O" Rings may not be the same as what is avaikable thru your hardware and bearing dealers. I have always ordered them by Jeep Part Number 800986.
Last edited by Joe Gopan on Tue Jun 12, 2018 4:44 am, edited 2 times in total.
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Re: Engine Smoking Opinions

Post by Shug4 » Mon Jun 11, 2018 12:50 pm

I thought that grey smoke was a sign of water in cylinders and black smoke a sign of carburetor needing adjustment and blue smoke was oil being burned

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Re: Engine Smoking Opinions

Post by Joe Gopan » Mon Jun 11, 2018 7:28 pm

Kind of strange that no one knows how the F-134 intake valves are sealed. The answer is in the Jeep Factory Service manual.
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Re: Engine Smoking Opinions

Post by g.keating » Mon Jun 11, 2018 10:02 pm

Since this forum is designed to help others with their questions and offer help , I found this paragraph in a jeep service manual. It may offer some help



E-58. Valves, Springs, and Guides
The exhaust valves seat on the top of.the cylinder block with the stems extending down through. replaceable valve guides. The exhaust valves are actuated by the camshaft through exhaust vaive tappets. The exhaust 'valve springs are assembled and locked on the lower end of the exhaust valve ste!lls. The retaining locks are the split type, which fit m a recess on the valve stems and into the taper in the valve spring retainers.
Adjustment of exhaust valves is by means of the adjusting screw threaded into the upper end of the exhaust valve tappets. An exhaust valve rotator. used as a valve spring retainer is installed on the lower end of the exhaust valve. This valve rotator known as "Roto Cap", is a spring-loaded bali bearing device. On each'lift, or opening stroke of a valve, the rotator gives the valve a slight positive clockwise rotation.
The intake valves operate in valve guides in the cylinder head and are actuated by rocker arms. The rocker arms are actuated by valve push rods and the intake valve tappets. The intake valve springs, the intake valve spring retainers, and the intake valye .spring retainer locks make up the remainder of the valve operating parts. An intake valve spring retainer oil seal which encircles the upper end of the intake valve between ·the valve locks and' the tipper end of the valve guide controls the passage of oil along the valve stem guide.

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Re: Engine Smoking Opinions

Post by Joe Gopan » Tue Jun 12, 2018 4:41 am

And when the "O"Rings are just dropped on the intake valve stems as in the photo, the result is smoke and lots of it if the valve guide clearance is excessive the smoke is even worse, all this from a simple 5 cent part. Simply installing the special O Rings into the valve spring retainer per Jeep instructions will eliminate the problem. Not many with "F-Head experience on the forum.
Thanks Gary, that's what I was waiting for. Did anyone else try to look this up in their manuals?
The Automobile machine shops and engine rebuilders are normally aware of these special seals and they are included in Jeep Engine overhaul gasket sets as well as Valve Grind sets.
Those O-Rings are Willys Part Number 800986 and are called "PACKING" I used to order these direct from Jeep by part number in packs of 100 in order to keep a stock of them as they are easy to lose on the shop floor.
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dlevy
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Re: Engine Smoking Opinions

Post by dlevy » Tue Jun 12, 2018 5:26 am

Thanks guys. 2 questions?

With the valve seal correctly placed in the retainer, how does it actually work to limit oil down the valve guide? It would move up and down within the retainer, so it is just sealing oil running down from the top?

The 2nd question is back to my head specifically.

I brought the head back to the engine shop to check it because he initially thought that the seals were correctly installed. He wanted to vacuum check the intake port and check valve guide clearance, etc. While he had it there he cut the valve guides down and put on positive lock valve seals that press on over the end of the valve guides. He also put the o-ring seals in the correct position on each valve.

I am concerned that I have 2 valve seals now and I will burn out a valve. Would you:
- leave it as it
- take off the head again, put in new valve guides and the correct seals
- pop off the positive lock valve seals and leave the cut valve guides alone

Appreciate your thoughts.

Dave

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Re: Engine Smoking Opinions

Post by Joe Gopan » Tue Jun 12, 2018 8:12 am

You will not burn out a valve with both seals installed, it will be just fine. Jeep chose to use O-Ring type seals, there are a couple of commonly used seals that do a similar Job to squeegee off excess oil from the Jeep intake valves, one is called an "Umbrella seal" which could require a slight modification to install. The intake valves are subject to vacuum which can draw excess oil during the intake stroke, the Jeep method works fine when the O-Rings are installed as directed, you now have double protection.
CCKW has Hat Shape Steel Shields over the intake springs that minimize the splash for the very same reason....
Hopefully, more G-503 participants who work on their "F-Head Jeep will be aware of this little detail.
I have witnessed the wrong or omitted installation of these O-Rings quite a few times since the 50's.
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KiwiMB
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Re: Engine Smoking Opinions

Post by KiwiMB » Wed Jun 20, 2018 8:46 pm

Hi Dave,
burned out inlet valves are very uncommon, and as Ben has said, you will not burn a valve by installing 2 types on stem seal. Burned out valves are more commonly caused by combustion gases blowing between the valve and the seat, this acts like a gas cutting torch. The blowing gas can be caused by tight (or no ) tappet clearance or wear between the valve and seat.
Just thought it would be helpful to understand how this happens to allay your concerns.

Cheers

Ian
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