Thats the only way I know how to prime it with oil. Soak all the rods and oil pump in oil. spin the oil pump under the oil to pull oil through it, fill your oil filter and get a priming tool to pump the oil through the engine and up into the heads.

I think your compression will jump way up when you crank it with a starter motor, and all the plugs out. I once changed my gear reduction starter from a 3.75 ratio to a 4.1 or 4.2 ratio. I had the 468 BBC engine out of my drag car to do some work and checked the compression before I put it back into the car. It was only around 165 psi and it was usually closer to 195 psi? I didn't think it could be the starter but couldn't find anything else wrong, so I reinstalled the old 3.75:1 starter and to my surprise the compression jumped 25 - 30 psi due to the faster speed of the 3.75:1 starter.

And there is what show’s you the trick we used to use with ‘cranking compression’ rules in circle track way back when. Slower we could crank (ie less engine rpm) the lower the cranking compression was.

Heres a compression gauge question for you SB, what brand gauge do you use in your shop, Im going to smash our snapon one into pieces and throw it off a cliff and was wondering IF you used a Snap on and your experience with their FAWKING valve cores!

I never owned a snap on compression gauge but I also went through the gauge accuracy questions. I would borrow 1 or 2 gauges from friends and then test the same cylinder with my gauge and the other two. Found up to 20 psi difference. Took my gauge and the higher one and connected them to a welding bottle with the regulator set to a certain pressure and then checked both gauges at that pressure to determine what they read. Mine was off about 15 psi and my friends was off about 5 psi. Sometimes it is the seal on the threads of the compression gauge that cause leaks or even the valve.

snap on. Approx 20-25yrs old ? Maybe 30 ? And a cheap actron. 15-20yrs old ? Both read within several psi of each other.

Correct me if I am wrong, but…. I was always told NOT to crank a new engine until I was ready to start it. This was especially true if it had a flat tappet cam. The cranking will remove some of the assembly lube and could lead to premature wear. I have always done it this way and never had an issue but am I being overly cautious?

So I have had numerous compression gauges thru the years/ My Snap on on is the most ergonomic/durable with its rubber coated gauge with exception of the damn schraeder valve . BUT the ONLY schraeder valve that works in it is one thats super soft and it breaks the spring every other time we use it then it doesnt work at all. NOTHING we have bought locally works in it either, so its a snap on only valve, full blown BULL SH##! . I wondered if you've had problems with them springs on valve breaking

That sucks.
I did have one (15yrs ago ???) that the Schrader on the psi release button thingy broke. I had acquired it somehow, so i have no idea it’s vintage. I do remember it being fine for a year or two once i ended up with it.

Note: i maybe use a compression gauge 5-10 times a year ? Not often, that’s for sure.

I’m no SnapOn tool fan. Too much $$$ for my cheap ass. Lol. I have just a handful of there things….if that.

Its strange that if I stick a ac valve core, valve stem valve core, milton valve core in it, we cannot get a good reading at all, will read 50 to 75 lbs at best on a 150 lb engine. With this super spongy soft core they sell on the tool truck (2 for 10.99), it works perfect.