This was only post I found on the subject. I have a screw in tester. this is the first v8 I've tried to use it on. It's been very hard to get it started into the holes. No straight shots and not much room. Never thought I'd say this but Been thinking the push in type would be simpler. Am I just getting to impatient in my old age??
I've got the Craftsman set and is definately a nice set. I used one of the rubber end ones before and it worked but hard to use unless you have a crank trigger to turn the engine over while holding the rubber end in place. Haven't used the new one yet though. - Matt
I bought a tune up kit years ago that included one of the press fit compression testers. I didn't care for it at all. I bought a new K-D Tools compression tester with the threaded adaptor a couple of months ago when I wanted to check the compression on my 302. I think it was money well spent. You have to be a little patient to find the right angle when you're trying to screw it into the cylinder heads, but I think you get more accurate compression readings.
The rubber ended ones are terrible because, if it is a tight fit and hard to get to the spark plug hole, it is hard to get the thing seated properly. If you dont get it seated just right you will get a bad reading. Go with a thread-in tester.
My brother taught me to use thread in units but to also put a little anti-sieze on the threads for sake of easy install and thread seal. Most quality units will have nice clean threads and a rubber o-ring to help seal.