Spark plug thread size.

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Model T Ford Forum: Forum 2016: Spark plug thread size.
Top of pagePrevious messageNext messageBottom of page Link to this message  By Jonathan Delancey on Thursday, August 25, 2016 - 12:48 am:

Looking to buy a compression tester. What size is the threads on the plug holes? Testers say they are good for 12mm 14mm 18mm. Not sure what to get.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Thursday, August 25, 2016 - 12:51 am:

They are modern plug sizes, T's are 1/2" pipe thread.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Corey Walker, Brownsboro TX on Thursday, August 25, 2016 - 12:57 am:

They are 1/2 inch pipe thread. You can get a spark plug adapter for 14 mm plugs then use the 14mm tester will work. Vendors sell those adapters, don't know if you can buy just 1. So body explained how they made their own a week or so ago but don't know how to find it


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Thursday, August 25, 2016 - 12:59 am:

The vendors sell an adapter, 1/2" pipe thread OD and 14mm ID


Top of pagePrevious messageNext messageBottom of page Link to this message  By Troy Todd on Thursday, August 25, 2016 - 01:10 am:

Looks like Ebay has several starting at about $19 each.

Innovative Products Of America 7885 Spark Plug Hole Adapter 18mm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Troy Todd on Thursday, August 25, 2016 - 01:11 am:

Sorry gave the wrong part # and don't know how to edit.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Troy Todd on Thursday, August 25, 2016 - 01:14 am:

Lang's has them for $15 for 4.

14MM-AD


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Thursday, August 25, 2016 - 01:16 am:

Far to much Troy, Langs are $14.95 for a set of 4.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Thursday, August 25, 2016 - 01:18 am:

oops! we are both on the same track now!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jonathan Delancey on Thursday, August 25, 2016 - 02:35 am:

All the testers I see go to 300 psi! Where can I get one that goes to only 100 psi?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jonathan Delancey on Thursday, August 25, 2016 - 04:27 am:

I just made an adapter with a 1/2" npt plug. Should work.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Thursday, August 25, 2016 - 06:23 am:

Jonathan, here's a thread discussing how to get a 100 psi tester: http://www.mtfca.com/discus/messages/257047/276119.html?1332284570

But I think you'll get a somewhat useful result with a 300 psi tester too - even your thumb will tell if one of the cylinders has significantly less compression than the others - and if some oil down through the spark plug holes improves compression :-)

(if oil improves compression significantly , then the rings are less than perfect - and if nothing is improved with oil but still low, then it's a valve problem.)


Top of pagePrevious messageNext messageBottom of page Link to this message  By G.R.Cheshire on Thursday, August 25, 2016 - 08:40 am:

I have an old one with a "universal" rubber tip just shove it in there and have someone turn the engine over a couple of times take the reading then press the release button and move to the next cylinder :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim Wrenn-Monroeville OH on Thursday, August 25, 2016 - 09:44 am:

Gosh, I bought an adapter from someone online a couple of years ago when I got my compression tester but unfortunately can't remember where. Only paid about $5 for it and I think shipping was even included. Don't know how they do it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Thursday, August 25, 2016 - 11:04 am:

I use my Craftsman screw in 300LB compression checker all the time. Works fine at the low range. I think the reason it works at the low range is because it's the screw in type and holds the seal better then a universal rubber tip type. I have found that it does not matter if the throttle is open or closed I get the same readings, the T has such low compression anyway.
Pull all the plugs, put it in, crank over thru 4 or 5 compression strokes, read, write down the number, repeat. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas Mullin on Thursday, August 25, 2016 - 12:01 pm:

Jonathan,

I bought a 0 to 100 psi gauge at Graingers.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Friday, August 26, 2016 - 05:08 am:

Buy a different gauge and replace the original one Johnathan. I replaced my 300 lb gauge with a 0-80 lb, 6" diameter one that's easy to read.

Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Friday, August 26, 2016 - 09:46 am:

I have a Matco 300 PSI compression tester that uses ordinary air tool connectors at the spark plug hole. I went to Home Depot and bought a 1/2" NPT - 1/4" NPT bushing reducer to make it fit the Model T sized spark plug hole. The reducer was something like $2.50 including tax.

No reason to search out a lower PSI gage, the 300 PSI gage is plenty accurate.

Like this only brass:
http://www.ebay.com/itm/NEW-1-2-NPT-to-1-4-NPT-304-SS-STAINLESS-STEEL-PIPE-BUSHI NG-REDUCER-/152205925790?hash=item23702e1d9e:g:RhcAAOSwHoFXsQv4


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