[AT] 1935 JD B Testing progress.

[John Hall]

Been following a bit about compression testing and such diagnosing 
engine problems with our old stuff. Since everything I have (almost) is 
old and high houred, engine wear is an issue. Got a combine with a gas 
engine that is burning oil bad. Mechanic friend came over to show me how 
to do a leak down test. He brought his tester and provided assistance. 
For those not familiar, you roll the engine up on compression and send 
compressed air into the cylinder thru the spark plug hole. We held the 
engine still with a pull handle on the crankshaft pulley.

With the oil filler and radiator caps off, you pressurize the cylinder. 
If one of the gauges on the tester shows a leak you look for the escaped 
air. If it goes into the crankcase, combustion chamber issues. Air thru 
muffler or intake then exhaust or intake then valve issues Bubbles in 
the coolant then a failed gasket or cracked head/block/cylinder wall.

Anyway, 1 cylinder was almost perfect, 2 showed wear but not enough to 
worry about, the fourth however was horrible--stuck or broken 
ring/scored cylinder Too close to harvest to attempt pulling the engine 
for a repair so I ran a bunch of Sea-foam in the oil as well as soaked 
the bad cylinder. Changed it and added some Risolone.  We did all this 
testing because we were suspect of valve seals. It only took 15 minutes 
to determine we had serious blowby on 1 cylinder. I have since bought a 
tester--I got one that covered 4 different spark plug sizes. Its a quick 
and simple game changer to determine what you have going on.  Anyway, 
might be a tool some of you wish to add to your to the shop.

Meanwhile I have to figure out how to pull a combine engine inside this 
winter--wish I had a larger shop or a gantry crane. Tossing around a few 
ideas.

John Hall


On 11/25/2020 8:46 PM, Dean VP wrote:
> I think I found the real problem on my 1935 JD B today.  I applied 30 psi of
> air pressure to the carburetor inlet side of the manifold and air was
> rushing out the exhaust pipe with all valves closed.  Apparently I have a
> rust out in the manifold or a blown gasket between the input and exhaust
> side of the manifold.  Started pulling the head today and have everything
> loose except the water hoses. Will soon have everything off to see if
> anything is visible.   I was hoping I wouldn't have to remove the manifold.
> The manifold studs will not come out without twisting off. I'm going to try
> to use a nut buster on the top nuts and see if I can get the nuts off
> without breaking the studs. Then try to remove the manifold.  Was hoping I
> wasn't going to have to do this but I'm glad I found the problem.  Will
> probably be looking for a new reproduction manifold or good used one.
> Leon???  Real progress today.
>
> Dean VP
> Apache Junction, AZ
>
> -----Original Message-----
> From: AT <at-bounces at lists.antique-tractor.com> On Behalf Of Dean VP
> Sent: Tuesday, November 24, 2020 9:35 PM
> To: 'Antique Tractor Email Discussion Group' <at at lists.antique-tractor.com>
> Subject: Re: [AT] 1935 Testing progress.
>
> The later JD All Fuel JD B's, which had higher HP, had a compression of
> 70psi. Haven't found a reference for the earlier JD B"s.  But it surely
> wouldn't be higher than 70.  The difference between cylinders of 7 1/2psi is
> pushing the limits of acceptability.  These tests were with the tractor
> cold. The compression test is supposed to be run when the tractor is a
> running temperature. The next test to run is the manifold leakage test. Then
> I probably will install the magneto and carburetor and get it running so I
> can do a high temperature compression test.  I may just pull the tappet
> cover and see if the lash is set right on the valves first. Now that I have
> the right tools to do the testing I Can make some progress.
>
> Dean VP
> Apache Junction, AZ
>
> -----Original Message-----
> From: AT <at-bounces at lists.antique-tractor.com> On Behalf Of Dean VP
> Sent: Tuesday, November 24, 2020 7:43 PM
> To: 'Antique Tractor Email Discussion Group' <at at lists.antique-tractor.com>
> Subject: [AT] 1935 Testing progress.
>
> Was able to get the 1935 JD B out of storage and since I had the carburetor
> and magneto removed during the winter storage we just pulled it to new
> location for the winter. Since we were pull moving anyway I asked my friend
> to pull me in gear  about the distance of the two blocks with the plugs out
> to get the oil pressure built up for the compression pending compression
> testing.  Then hooked the compassion tester and 7/8" to 154 MM adapter up
> and had him pull me a 100 feet or so in gear and tested compression on each
> cylinder.  Thew results were not as expected.   Got about 62 1/2" psi on the
> left cylinder and about 55 psi on the right  cylinder.  I expected a much
> larger difference between the two.  Not sure what it should be but sone
> reason I expect 70 psi but I don't remember where that came  from.  But the
> 7 1/2psi difference by itself tell me I need to tear into this tractor.,  I
> don't think.  Tomorrow I can do the manifold air pressure test.  If I can
> complete that. He results o
>   f that test will determine what I test next,
>
>
> Dean VP
> Snohomish, WA 98290
> "Socialism is a philosophy of failure, the creed of ignorance, and gospel of
> envy, its inherent virtue is the equal sharing of misery."
> ..Winston Churchill...
>
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