This site uses cookies to maintain login information on FarmallCub.Com. Click the X in the banner upper right corner to close this notice. For more information on our privacy policy, visit this link:
Privacy Policy

NEW REGISTERED MEMBERS: Be sure to check your SPAM/JUNK folders for the activation email.

Spark Plug Leak

The Cub Club -- Questions and answers to all of your Cub related issues.
Forum rules
Notice: For sale and wanted posts are not allowed in this forum. Please use our free classifieds or one of our site sponsors for your tractor and parts needs.
User avatar
ScottyG
10+ Years
10+ Years
Posts: 422
Joined: Sun Jul 18, 2004 7:49 pm
Location: Watkins Glen, NY

Spark Plug Leak

Postby ScottyG » Fri Nov 19, 2004 9:28 am

Anyone have a quick solution for a leaky thread on spark plug #3 for my Cub? I used teflon pipe dope (yeah I know probably won't withstand the temp) which seemed to help control some of the blow through but I was wondering whether there was something industrial out there that is typically used?
"Henry" 1948 Farmall Cub

SPONSOR AD

Sponsor



Sponsor
 

Jim Becker
Team Cub
Team Cub
Posts: 17240
Joined: Sun Feb 02, 2003 2:59 pm
Zip Code: 55319
Circle of Safety: Y
Location: MN

Postby Jim Becker » Fri Nov 19, 2004 9:31 am

A new gasket?

Ron L
10+ Years
10+ Years
Posts: 661
Joined: Wed Mar 05, 2003 9:09 pm
Zip Code: 18603
Tractors Owned: 1948 Cub
1955 Cub
Location: PA, Berwick
Contact:

Postby Ron L » Fri Nov 19, 2004 9:31 am

Maybe a copper washer would work ? Untill you can get the threads repaired...........
Ron

User avatar
George Willer
Cub Pro
Cub Pro
Posts: 7013
Joined: Sun Feb 02, 2003 9:36 pm
Zip Code: 43420
Circle of Safety: Y
Location: OHIO, Fremont
Contact:

Re: Spark Plug Leak

Postby George Willer » Fri Nov 19, 2004 9:56 am

ScottyG wrote:Anyone have a quick solution for a leaky thread on spark plug #3 for my Cub? I used teflon pipe dope (yeah I know probably won't withstand the temp) which seemed to help control some of the blow through but I was wondering whether there was something industrial out there that is typically used?


Scotty,

Don't worry about the teflon holding up to the heat. A fellow model builder makes his own spark plugs. When I expressed surprise that he could make the insulator he said he uses teflon. When I questioned its' ability to withstand the temperature he said the plugs don't get hot enough to keep from fouling. The oil will burn off a plug a couple hundred degrees below the limit for teflon.

I agree that cleanliness and a good gasket should stop the leak, however.
George Willer
http://gwill.net

The most affectionate creature in the world is a wet dog. Ambrose Bierce

User avatar
ScottyG
10+ Years
10+ Years
Posts: 422
Joined: Sun Jul 18, 2004 7:49 pm
Location: Watkins Glen, NY

Postby ScottyG » Fri Nov 19, 2004 11:31 am

These are all great suggestions but let's talk about repairing the threads for a second. In order for me to do this, I'd think that I'd need to retap the head rather than to chase the existing thread. Now we're into a whole different world of which I know nothing about whatsoever. Size of the new plug vs. required plug rating, etc since the threaded end of the new plug would be physically bigger.
"Henry" 1948 Farmall Cub

User avatar
Bigdog
Team Cub Mentor
Team Cub Mentor
Posts: 24144
Joined: Sun Feb 02, 2003 12:50 pm
Zip Code: 43113
Circle of Safety: Y
Location: OH, Circleville
Contact:

Postby Bigdog » Fri Nov 19, 2004 11:38 am

I believe Heli-coil has a thread repair kit for sparkplugs.
Bigdog
If you can't fix it with a hammer, you've got an electrical problem.

My wife says I don't listen to her. - - - - - - - - Or something like that!

Image

http://www.cubtug.com

Eugene
Team Cub Mentor
Team Cub Mentor
Posts: 20344
Joined: Fri Jul 02, 2004 9:52 pm
Zip Code: 65051
Circle of Safety: Y
Location: Mo. Linn

Spark plug hole repair

Postby Eugene » Fri Nov 19, 2004 11:53 am

It's been quite some time. I purchased and used a repair kit for spark plug holes from the local auto parts store. It was designed for and used on an aluminum engine. Basically. It was a self tapping bolt to cut new threads and an insert installed with a socket.

Jim Becker
Team Cub
Team Cub
Posts: 17240
Joined: Sun Feb 02, 2003 2:59 pm
Zip Code: 55319
Circle of Safety: Y
Location: MN

Postby Jim Becker » Fri Nov 19, 2004 12:22 pm

How did we jump from a leaky thread that wouldn't hold pressure to one that wouldn't hold the spark plug in the hole? What is wrong with the threads in the head?

Get more specific and maybe we can give better suggestions.

User avatar
John *.?-!.* cub owner
Cub Pro
Cub Pro
Posts: 23701
Joined: Sun Feb 02, 2003 2:09 pm
Zip Code: 63664
Tractors Owned: 47, 48, 49 cub plus Wagner loader & other attachments. 41 Farmall H.
Location: Mo, Potosi

Postby John *.?-!.* cub owner » Fri Nov 19, 2004 2:01 pm

Scotty, are you sure there isn't some dirt on the surface where th plug seats. The plugs on a cub have a metal gasket that seals them against a flat spot on the head, they don't use a pipe thread seal like Ford cars do. Also are you sure the leak is coming from where the plug screws in, and not between the metal and porcelain of the plug? I've seen that happen more than once.
If you are not part of the solution,
you are part of the problem!!!

User avatar
ScottyG
10+ Years
10+ Years
Posts: 422
Joined: Sun Jul 18, 2004 7:49 pm
Location: Watkins Glen, NY

Postby ScottyG » Fri Nov 19, 2004 3:11 pm

Well I suppose it could be leaking between the plug gasket and the porcelin but this particular plug I've consistently had to play with in order for it to thread in correctly which usually means that someone cross threaded at one time or another. Basically, I just assumed that it was the threads in the cast causing the problem. When I refurbed the tractor, I was careful to insure that all dirt and paint were removed from the metal gasket in the head. I didn't know that the Cubs don't rely on pipe thread to seal so I've learned something there.

Once the plug is in, it does seat firmly. It's just that I've noticed some blow through next to the plug by a visible sooty mark nearby that develops right away. This will, as Jim pointed out, reduce pressure so I want to stop the problem. If I can replace the gasket under the plug, that's what I'd opt for. Later in the thread, I was just curious as to what people normally do to retap plug threads.

I think I'll try using a copper washer and see if that does the trick. Any other suggestions would be greatly appreciated.
"Henry" 1948 Farmall Cub

Ron L
10+ Years
10+ Years
Posts: 661
Joined: Wed Mar 05, 2003 9:09 pm
Zip Code: 18603
Tractors Owned: 1948 Cub
1955 Cub
Location: PA, Berwick
Contact:

Postby Ron L » Fri Nov 19, 2004 4:50 pm

Scotty. Spark plugs do not rely on the threads alone to seal. They usually come with a gasket (looks like a double washer) that seals the pressure. Some without washers have a tapor just above the threads to seal (like your valves). I never heard of a spark plug with NPT threads. Cub plugs are 18mm thread size. It is possible some one tried to clean out the threads with a standard tap or straight pipe threads. Regardless, you should check the flat surface where your plugs go in to see if it there is gouges or something else causing pressure to blow out. That is why both Jim & I suggested a gasket (new gasket or copper washer) and as GW suggests (good to see his posts again!!! ) make sure your clean around the plug area. Hope this helps..........
Ron

User avatar
John *.?-!.* cub owner
Cub Pro
Cub Pro
Posts: 23701
Joined: Sun Feb 02, 2003 2:09 pm
Zip Code: 63664
Tractors Owned: 47, 48, 49 cub plus Wagner loader & other attachments. 41 Farmall H.
Location: Mo, Potosi

Postby John *.?-!.* cub owner » Sat Nov 20, 2004 10:39 am

Ron L wrote: I never heard of a spark plug with NPT threads. .
Thanks for catching my error. I intended to type that the tapered ones seal like pipe threads, but my typing and thinking sometimes don't follow each other. Guess I'm going to have to start proofreading closer.
If you are not part of the solution,
you are part of the problem!!!

User avatar
beaconlight
10+ Years
10+ Years
Posts: 7703
Joined: Thu Aug 19, 2004 2:31 pm
Zip Code: 10314
Location: NY Staten Island & Franklin

Postby beaconlight » Sat Nov 20, 2004 11:17 am

APO had installed tapered plugs in my Low Boy. The blow by had formed carbon in the threads. I had to use a 3 foot pipe on a 1/2 in breaker bar to get them out. I ground flutes similar to a tap in an old plug and used that to chase the threads. I grould away some of the metal on the plug as well so that I could clean deep in to the hole. That was the sunday evening shade tree mech idea that fixed my problem. With the added compression I thou ght that I had an engine overhaul.
Bill
Bill

"Life's tough.It's even tougher if you're stupid."
- John Wayne

" We hang petty thieves and appoint the great ones to public office."
- Aesop

User avatar
George Willer
Cub Pro
Cub Pro
Posts: 7013
Joined: Sun Feb 02, 2003 9:36 pm
Zip Code: 43420
Circle of Safety: Y
Location: OHIO, Fremont
Contact:

Postby George Willer » Sat Nov 20, 2004 11:31 am

Ron L wrote:Scotty. Spark plugs do not rely on the threads alone to seal. They usually come with a gasket (looks like a double washer) that seals the pressure. Some without washers have a tapor just above the threads to seal (like your valves). I never heard of a spark plug with NPT threads. Cub plugs are 18mm thread size. It is possible some one tried to clean out the threads with a standard tap or straight pipe threads. Regardless, you should check the flat surface where your plugs go in to see if it there is gouges or something else causing pressure to blow out. That is why both Jim & I suggested a gasket (new gasket or copper washer) and as GW suggests (good to see his posts again!!! ) make sure your clean around the plug area. Hope this helps..........


Since the Cub plugs are 18MM straight thread this doesn't really apply, but there were a lot of plugs made with tapered pipe threads. The most notable I can think of was the model T Ford. Some early tractors and hit and miss engines also used them. I'm not certain, but I think our John Deere GP that I haven't seen since 1947 had them as well.
George Willer
http://gwill.net

The most affectionate creature in the world is a wet dog. Ambrose Bierce

Ron L
10+ Years
10+ Years
Posts: 661
Joined: Wed Mar 05, 2003 9:09 pm
Zip Code: 18603
Tractors Owned: 1948 Cub
1955 Cub
Location: PA, Berwick
Contact:

Postby Ron L » Sat Nov 20, 2004 11:53 am

Thanks for the insight, George. When I said "I never heard of NPT threaded spark plugs", I should have added "with my limited knowledge of the subject"! John, it was in reference to Scotty's post. NPT threads would surely hold plenty enough pressure, but gosh, what a bugger to get them out if left in for years like some cubs!! Probably why modern plugs go strictly with gaskets (as far as I know, with my limited knowledge!). This is just the MACHINIST in me talking...............
Ron


Return to “Farmall Cub”

Who is online

Users browsing this forum: No registered users and 33 guests