WTB:Compression tester for 1/2" thread

[John Gelfer]

All modern testers come with 14mm and 18mm adapters, but none have 1/2" pipe thread, which is what most of us need for antique cars. I tried cutting off the 18mm male, and stuffing a 1/2" hose barb into the hose. It doesn't work! Seems like it should. Any ideas on where to buy one?

[nickelroadster]

I had the same problem with 7/8" threads. I just took an old spark plug and punched the innards out and then threaded the inside so I could just screw the hose in that way. It works great.

[TheMoneyPit]

Most of the model T parts vendors carry an adaptor to put a 14mm plug into the T head - aka 1/2" pipe thread. Could this be easier? Or buy a reducer 1/2 NPT to 1/8 NPT and do the same as above thread suggests.

[Larry Schramm]

Personally I agree with Nickelroadster. Just take an old sparkplug and cut the top off and tap the center and it works perfectly. The inside of the sparkplug shell has a taper that allows for a good seal.... at least on my compression tester. :-)

[TexRiv_63]

John,

I had this problem with my Pierce. I bought a compression tester from NAPA that had two different extensions with cone shaped rubber ends instead of threaded. One of the old sparkplugs was designed to come apart so the insulator comes out. I used the base part screwed into the head and just held the rubber cone down on the top of it while my wife spun the motor over, worked great. Also used it for my Cadillac.

[Jay Wolf]

I used and old spark plug and brazed and quick air disconnect in to the hooks to both my leak-down and compression gauges.