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.

Don't worry too much about gas and flooding and such. Only the cylinder with the compression tester will actually be drawing fuel, as the other cylinders have no plugs in them (therefore no vacuum to draw the fuel).

Opening the butterflies doesn't do much for the compression readings. At cranking RPMs, you might draw 2-3" of vacuum at best, which may reduce your compression reading by as much as 1-2 psi. Your tester is graduated in 5 psi increments. I do it anyway, just like I don't store car batteries on concrete, even though I KNOW it doesn't make a difference.

Sorry to threadjack but I never heard of this before, can you explain?

Nope, I can't. I'm sure Mythbusters could do a whole episode on the destructive properties of concrete, pertaining to fuel, car batteries, planters warts, etc.

(Concrete floors are supposed to kill car batteries, or so goes the wives tale. Google "Concrete Battery" for some fun reading)

Thanks for the info on the compression test.

I've always stored car batteries on plywood too and I always figured it was superstition.

Dustin

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.

Grounding the coil is supposed to be good for it, probably another wive's tale I tend to follow if necessary. Better yet is to pull the power to the coil.

Awesome. Thanks you guys for the advice on the valve adjustment. I might not finish tonight because it took me a bit to get my groove and I have to get some other things done, but your explanations were really helpful.

Dustin

One thing that I missed is that any wear on the rocker arm contact pads make setting the valves impossible as the feeler gauge will not measure the gap correctly between the valve and the rocker. They wear a little grove in the bottom and need to be resurfaced. Pull off the rocker shaft and check them for wear (I don't do this routinely, but I've resurfaced my rockers - so I know they were fine when I set my valves). They will probably need to be done. Every set of rockers I've pulled off of a B18/B20 needed to be surfaced. Unfortunately no one does these anymore in any machine shop I checked in town. I do my own with my belt sander. You need a delicate touch and a fine belt (220), but it isn't hard.

I pretended to have not read Craig's advice on checking for wear, and I fired up the car. It ran horribly. I set it to the gap it gives in the manual though, not to what you recommend above.

I pulled the rocker shaft and there was no noticeable wear at all. It seems smooth and convex. I'm going to recheck everything and set it tighter like recommended above and see what happens then. I'll get to the bottom of it.

Dustin

Describe horrible? Did you mark and double check the rockers?

It ran super rough and shook. I haven't been able to get back out to the garage yet.

Something I noticed was that a couple of the rockers seemed to be at a slight angle on the bottom surface, as if one half of it would be hitting the valve before the other. I couldn't tell if they were worn that way when I pulled the rocker shaft off, but I wasn't looking for that. It seemed that way when I was sliding the feeler gauge under there.

So I'm looking forward to going out and doing it again, to a tighter tolerance like you say above.

I didn't mark the valves like you said, but I felt like I was being super careful. I used the list on the Haynes manual as a checklist, and I checked them all after I was done. I'm comfortable that they're set to the 0.020-0.022 spec in the manual, but I want to go back and tighten if up like I said. I'll also mark them this time, to be totally sure.

I'm not worried. This is all new to me and I'm having tons of fun learning it. Thanks for taking the time to help out.

I just realized that it's colder than heck out there in my garage. I think about 5C. I'm setting it to the cold spec but maybe it's TOO cold.

Dustin

Ya, that's way too loose. It would only affect the noise/performance. It shouldn't make the car shake etc. What else changed?

I'm thinking one's too tight and is hanging a valve open...

I still haven't made it out to the garage due to a fear of freezing my fingers off. The temperature is supposed to warm up a lot tomorrow and continue throughout the week so I should be able to get out there soon.

The only other thing I did is pull out the spark plugs to make it easier to turn the motor. I marked the wires with numbered clothespins as suggested and I was very careful about that. Maybe I somehow screwed up a plug or a wire and it's firing on 2 or 3 cylinders instead of 4.

Regarding one of them being too tight, that could be. I'm going to go over them again very carefully and then check my plug wires and my plugs. That car needs new spark plugs anyway.

Update:

The car's running and the compression is strong and consistent: 160, 154, 158, 154

An issue I couldn't have figured out for myself is that the timing isn't advancing when the car revs. John P came over and helped me diagnose it. He also redid my valves, but I wasn't really off when I did them from what I could see.

I spent some time cleaning the carbs because they're gunked up. Now that this car is in my garage I've been going over it more carefully. The generator mount is messed up. The hole the bolt passes through has widened up and the generator swims around a bit. I cranked it down tight and it's fine for a bit but I want to put a new 1-wire alternator in. I've seen stuff on this forum about it so I'll search for that shortly.

A front bumper mount is broken or rusted out too, and someone did a crappy repair that failed. It means the bumper kind of swings in towards the tire. I'll take a closer look at that soon.