Compression Gauge Kit- recommendations

[29 Chandler]

Looking for some recommendations on a decent engine compression gauge kit. I work on cars from 1914 to 2008 and some times small engines. I have no faith in my cheap compression gauge that I bought 40 years ago as a teenager. Looking at Amazon I see so many brands that I don't recognize. 

 

Since I am servicing a wide range of engines looking for a kit that adapts to the different plug sizes as needed.

[Bloo]

Snap-On. I'm not kidding. Yes it's expensive. Mine is 30 or 40 years old and is about like this:

 

 

Note there are 3 adapters. 14mm long, 14mm short, and 18mm short. This covers most cars.

 

Stuff it won't cover is brass and nickel era cars with tapered pipe threads or the rarely seen inch threads. In those cases though, adapters exist for those cars to "adapt" modern spark plugs to those engines. I'd consider getting one of each and just throwing it in the compression tester kit. It also won't cover 10mm plugs as used in some 40s Chevrolets and possibly Buicks. I wonder if Snap-On makes a 10mm adapter? Maybe. Many of those heads have that took 10mm plugs have been replaced. I doubt you will run into it.

 

If you get a Snap-On, order a bunch of their Schrader valves at the same time. The ones for tires just don't seem to get the job done. I made this mistake at first years ago when I bought mine. The tool truck didn't have extras in stock. Most people must not use these gauges very much. Compression testing beats Schrader valves to death.

 

Just looking online quickly, I see a bunch of kits that look like this:

 

 

Maybe there's 10mm in there somewhere.

 

If you opt for something cheaper, which probably makes sense for most people, you can get cheaper branded ones that work about like these, but come with one adapter that covers 18mm and 14mm threads on the same adapter. My leakdown tester has an adapter like that. It works for most cars. The trouble is in the 80s and 90s some cars have long 14mm plugs, but the threads do not begin until the last 1/2" or 3/8" of the length. The combination adapters won't work in those because they don't reach the threads.

 

 

That looks like they provided an adapter to get around the limitation.

 

Bare minimum I would want to see are a Schrader valve in the tip, a release button on the gauge, and a fitting to remove the hose so that it can be screwed in separately without the gauge attached.

 

Don't even consider units with a rubber tip you have to hold in place.

 

 

Edited June 11, 2023 by Bloo (see edit history)

[TTracing]

Ya I lent my 1970 gauge to a neighbor and that was the last I saw if it LOL    I bought the Craftsman set and have been very happy with it seem right on and I like the quick disconnect    I all so use it on every thing from a 9 sec race car to my lawn mower. 

[29 Chandler]

Thanks guys. There is now one less Snap On Compression Gauge kit on eBay 🙂

 

[Frank DuVal]

Try HVAC Schrader valves. 😉

 

 

[29 Chandler]

Just to close out this topic my "new" Snap on compression gauge arrived this week, it even came with a bag of extra valves. I tested it on the chainsaw I am rebuilding on the workbench right now and saw 160 lbs on the gauge vs. 30 lbs from the gauge I purchased new as a teenager in the 80's.

 

Thanks for steering me in the right direction.