Ugly Duck wrote:
The manual has it covered, though you should also do a few other things first:
Set your valve lash, because your lash can greatly influence your compression readings. Do this either cold or hot. I like to do it cold, and set them to the loose spec of cold. When doing it hot I am always conscious about the time spent, and how much I fear one valve might be cooling down compared to the others, thereby getting inconsistent readings. Also I can spend more time fiddling and farting and getting it perfect because I'm not burning my fingertips.
Get the engine up to operating temperature before checking compression. Doing a compression test takes much less time than setting valves, so worrying about the engine cooling down much over the course of the test is reduced, and your readings are more accurate when hot.
What Matt said...and I'd add a few things.
Not that I want to start the holly wars of valve setting, but for a B18/B20 many of the performance people tell you to set them a little tight. I usually go for 16 thou hot 17 thou cold (which are both on the tight side of what the manual suggests hot or cold). This is what I was told by Phil Singher some years ago (maker of the MPPE B20) it's worked for me ever since. I also don't follow the manual method for setting the valves.
Phil had done a lot of testing and told me that the method explained in the manual is mostly for set up at the factory (speed, efficient) and doesn't ensure that the lifter is on the base circle of the cam precisely. Most people prefer the "nine's" method...where the total of the valve being set + open valve = 9. For example, set valve 1 when valve 8 is fully down. I mark the valves with a marker (red) when set as I can't keep it straight and have made mistakes in the past. One dot means the valve has been set. Two turns of the crank gets all the valves set...I do it twice to check. Also don't torque the heck out of the adjuster nuts or you'll break stuff. Snug is plenty tight. Keep the screwdriver in the adjuster when snugging or the adjuster will move.
On compression testing:
I don't know why you'd ground the coil - just yoink the lead off it and put it somewhere while cranking. Pull all the plugs - I use clothes pins that I numbered to keep the wires straight and I put the plugs in my plug board to have a look-see at them. Then moving from the front to the rear, wind the gauge in the plug hole and make sure it's got a positive seal. Crank the starter until the pressure seems to stabilize. Record this as the hot value - dry. Then repeat for the other cylinders. Next squirt oil in the holes...just a few pumps in the hole being tested one at a time. Then crank again...this is the hot - wet value.
You are looking for consistency between cylinders more than a specific pressure value. Usually less than 5% between cylinders is fine. For my old B18, the pressures were something like 130, 98, 103, 125 hot - dry and the middle two went up a little wet, but were still not great. When I stripped the engine down, it was sharing compression between 2 and 3...which also explained why my cooling system would get pressurized when driving vigorously and why I literally blew my dip stick out of the hole on the highway one time (pressurized the crankcase and blew it and left a lot of oil over everything).
A healthy B18 is around 140 psi ... ish.