[AT] Spark Plug to Compression Tester adapter

Wed Nov 18 12:41:18 PST 2020

18MM would be about 0.7 inch, so it would not work in a 7/8  hole.

Carl

----- Original Message -----
From: Dean VP <deanvp at att.net>
To: 'Antique Tractor Email Discussion Group' <at at lists.antique-tractor.com>
Sent: Wed, 18 Nov 2020 13:02:59 -0500 (EST)
Subject: Re: [AT] Spark Plug to Compression Tester adapter

Just checked the Auto Zone Web site.  With the exception of one item, none offered adapters for spark plug sizes greater than 18MM.  Item CP7821 has only one rubber adapter, of unknown size, which in the description says " fits all spark plugs" I suspect that too would fit a maximum of 18mm.  Even if that rubber adapter would seal in an 7/8" spark plug hole it would not work on a hand start tractor very well,  Well, unless you have three hands. I suspect the use of 7/8" size spark plugs in new engines went the way of the dodo bird several years ago. 

Dean VP
Apache Junction, AZ

-----Original Message-----
From: AT <at-bounces at lists.antique-tractor.com> On Behalf Of szabelski at wildblue.net
Sent: Monday, November 16, 2020 5:00 PM
To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com>
Subject: Re: [AT] Spark Plug to Compression Tester adapter

The last time I did a compression test on the Cub, I rented a compression test kit from Auto Zone. It had a whole series of adapters that allowed for a standard hose to be threaded into the manifold. Don’t know what ranges the adapters covered. When you rent a tool from Auto Zone they basically sell you the tool, then refund you your purchase price when you bring the tool back. That way if you decide to keep it, you’ve already paid for it and they’re not any money. Maybe something to look into

Carl

----- Original Message -----
From: deanvp <deanvp at att.net>
To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com>
Sent: Mon, 16 Nov 2020 18:37:27 -0500 (EST)
Subject: Re: [AT] Spark Plug to Compression Tester adapter

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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