[AT] Spark Plug to Compression Tester adapter

[deanvp]

Will doSent from my Galaxy
-------- Original message --------From: Mitchell Daly <md31043 at msn.com> Date: 11/16/20  2:15 PM  (GMT-07:00) To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com> Subject: Re: [AT] Spark Plug to Compression Tester adapter 

Keep us up to date on your project.






Mitch
md31043 at msn.com









From: AT <at-bounces at lists.antique-tractor.com> on behalf of Dean VP <deanvp at att.net>
Sent: Sunday, November 15, 2020 11:31 PM
To: 'Antique Tractor Email Discussion Group' <at at lists.antique-tractor.com>
Subject: [AT] Spark Plug to Compression Tester adapter
 





For those of you who have tractors with 7/8” 18 TPI spark plugs and would like to do a compression test with the low cost compression testers kits sold today  you are SOL.  All the threaded as well as rubber stopper adapters are too small. The biggest is 18MM.
 7/8” is equivalent to just over 22mm.  Doing a compression test is impossible on a hand start tractor with that set up unless you can buy an adapter from 7/8” to one of the metric adapters in the compression tester kit.   I just found a company Billman Company
 that sells a few of those adapters of various sizes including one from 7/8” to 14 mm.  


https://brillman.com/?s=spark+plug+adapter&post_type=product

 

I was thinking I was going to have to make one out of the compression kit rubber stopper adapter and braze it into the inside of a gutted sparkplug.  This is a better solution in my mind.  When I receive this I will be able to test the compression on my Hand
 start 1935 JD B. Will be able to compare cylinders by hand cranking, using a belt on the pulley or pulling it in gear.   My current guess is the compression on cylinder # 2  is about half of #1 by the feel on the flywheel. We will soon find out.


 

I also want to make sure that the manifold isn’t rusted out or leaking from the intake side to the exhaust side. So I made an adapter plate that fists on the carburetor intake side of the manifold and then drilled and tapped a ¼” Pipe thread and installed a
 quick connect air fitting.  With the adapter plate bolted to the carburetor inlet to the manifold I can add air pressure to the intake side of the manifold.  If things were perfect I should get no air leakage into the exhaust side but the intake valves may
 open slightly and allow air pressure into the combustion chamber.  With the flywheel at TDC on #! Cylinder all the valves should be closed.  If I get a bunch of air pressure into the exhaust I know I have a manifold problem. If that passes then if  the intake
 valves open  and I get no leakage out of the exhaust side than I know I have a good manifold and two good exhaust valves.  If I get some leakage out the exhaust then I probably have exhaust valve problems.


 

 

Have to get the B out of winter storage here and start doing these tests. I brought 4 restored DLTX-10 Carburetors and 4 Magneto’s along so I can isolate if either one of those are causing me problems.   I hope I don’t have to pull the head on this tractor
 but my gut tells me that will be what happens as a result of the tests. Pulling manifolds on one of these old tractors is an exercise that usually ends up with 4 broken off studs in the head.  Broken off bolts don’t scare me like they used to but it takes
 a whole bunch of time and frustration to get everything cleaned up again ready for new studs. .  Maybe for once I will get lucky and not have to do major surgery.


 

 

 

Dean VP

Apache Junction, AZ






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