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Farmall & IHC Tractors Discussion Forum
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Spark Plug Tap

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Loren in Iowa

04-16-2008 20:16:35




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A little oil seeps past the spark plug threads, on our Farmall Regular. I'm thinking I should clean out the threads with a tap. Are they pipe thread? What size?




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Owen Aaland

04-17-2008 20:27:21




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 Re: Spark Plug Tap in reply to Loren in Iowa, 04-16-2008 20:16:35  
Original head would have 7/8-22 threads. I do not know if later replacement heads switched to the 18mm size or not. The letter series heads all have metric plug threads but the change may have occurred before 1939, maybe in the diesels?



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leroy in ne

04-17-2008 18:09:05




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 Re: Spark Plug Tap in reply to Loren in Iowa, 04-16-2008 20:16:35  
make sure the gasket seat in head is clean, no carbon or dirt residue from previous plug changes. i have used a small end type wire brush extended with a welded on rod or piece of tubing for this, turn by hand, no drills ect, blow out with air or vacuum with shop vac leroy



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randy hall

04-17-2008 12:18:22




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 Re: Spark Plug Tap in reply to Loren in Iowa, 04-16-2008 20:16:35  
7/8" 18 thread. they are not pipe thread.



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CNKS

04-17-2008 12:35:29




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 Re: Spark Plug Tap in reply to randy hall, 04-17-2008 12:18:22  
Question -- The plugs are 18 mm I think, so does your 7/8 18 thread mean 18 mm diameter or 7/8 hole, 18 threads/inch? 7/8 = 22.22 mm. Reason I ask is that the thread on one hole on my C had a cut or something all the way thru all the threads, plus a messed up seat -- took it to a machine shop and they could not find a helicoil for the hole. Took it to another place and the guy claimed he could fix it, but only machined the seat, did nothing for the threads -- It still has the cut, and I used pipe dope to keep it from leaking. It worked, but it is not a long term fix. I only use the tractor occasionally, but some day I want to fix it right.

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randy hall

04-17-2008 12:18:16




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 Re: Spark Plug Tap in reply to Loren in Iowa, 04-16-2008 20:16:35  
7/8" 18 thread. they are not pipe thread.



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Scott Rukke

04-17-2008 12:03:13




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 Re: Spark Plug Tap in reply to Loren in Iowa, 04-16-2008 20:16:35  
I notice no one asked if you have the metal o-rings in place on the plugs? The W-20 replacement plugs I just bought come with a nice copper ring to seal the plug against the block.



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Loren in Iowa

04-17-2008 16:54:15




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 Re: Spark Plug Tap in reply to Scott Rukke, 04-17-2008 12:03:13  
Seals are present.



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dave2

04-17-2008 04:38:28




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 Re: Spark Plug Tap in reply to Loren in Iowa, 04-16-2008 20:16:35  

Loren in Iowa said: (quoted from post at 20:16:35 04/16/08) A little oil seeps past the spark plug threads, on our Farmall Regular. I'm thinking I should clean out the threads with a tap. Are they pipe thread? What size?


first thing we did in auto shop was made SP thread chasers to clean the threads. Took used plugs, ground the little flange that holds the porzelain in place to remove it, ground off the electrode, and took a hacksaw and made two cuts (cross) through the threads. Will clean them without being tough enough to screw anything up.

Dave

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tn terry t

04-17-2008 04:20:47




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 Re: Spark Plug Tap in reply to sean mcdonnell, 04-16-2008 20:16:35  
I'd go with what Rustyfarmall said if your plugs will screw in there all you gona do with a tap is make them even" losser" making even more leaks i would maybe change the offending plug. the seat might be pitted. its niether here nor there if you have oil coming out you have more problems than a leaking plug



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James Williams

04-17-2008 04:08:37




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 Re: Spark Plug Tap in reply to Loren in Iowa, 04-16-2008 20:16:35  
They are pipe threads 7/8 I think

jimmy



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RustyFarmall

04-17-2008 03:09:22




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 Re: Spark Plug Tap in reply to Loren in Iowa, 04-16-2008 20:16:35  
There is nothing wrong with the threads. If there is enough oil getting into the cylinders that it seeps past the spark plug gasket, it is time for some engine repairs. But, before you tear into the engine, take that tractor out and make it work hard. That seepage problem might just go away.



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Dan Bear Kelley

04-19-2008 07:47:58




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 Re: Spark Plug Tap in reply to RustyFarmall, 04-17-2008 03:09:22  
I concur with Rusty. Work her hard! Get her good and hot so the carbon and junk burns off the valves. Also by working her hard, you'll get the rings loosened up real good. Both of those should get her to seal better. Also check the seals on your spark plugs. If the seals are all crushed, they won't seal.



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