I have a '70 B20E engine I want to do a compression test on. The engine is out of the car, so it would be pretty hard to get a warm engine compression test going.

Anybody know the difference of a warm compression test vs a cold compression test? I figure as long as the readings across the cylinder are consistent.

I guess dry vs wet compression test too? Does wet vs dry give you an indication of ring condition?

Paul

Unless the engine has been run very recently, there is no accuracy to a compression test. Overnight cold is fine, run briefly is fine, hot is fine, but if it has sat for any length of time, forget it.
Variation, not the specific number, is what is important.
It is a highly over-rated measurement, and one I use for diagnosis of a problem, rather than a maintenance or condition check. I just listen to the engine running, and can tell far more.

The engine haven't been run for a while.

Doesn't really seem to matter through with this engine. I think I got enough info on it with a compression check and a cam check.

First-#1 intake valve doesn't open all the way-> worn cam lobe. Rest of the valves open ok.

Second - Compression check (cold and dry) - 80 - 128 - 152 - 142 (not worth doing a wet check).
- I assume the low compression on #1 is due to intake valve not letting the engine breath correctly.

I guess the conclusion would be that this engine is worn out.

I did get the M410 (the 1800 version) with the engine, so not a totally lose.

Paul

A worn cam lobe will not affect cranking compression. Any amount open is enough at those speeds. In any event the head is coming off to do the cam, so it's a moot point.
If the engine block has no ridge, and has not been "ringed" before, then the block is also a valuable find. These engines are getting rare, and a good core is always worth something.

I have a B18 I think is good. My plan was to use the B18 in this car, but this B20 came up, and thought I would take a gamble on it.

So, no plan to rebuild this engine. I'll see if anybody local would be interested in it as a build.

I have two B20 engines that I'm sure could be used to build one really good (Megasquirt) engine. This B20E which is complete (including the D-jet injectors and intake), and a disassembled B20F (with a 8-bolt crank, block, pistons, and head)->which I was told it was a '75 engine.

Paul

The 74-75 head is highly prized by many. Will work fine on any B20 block.
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George Downs, Bartlesville, Heart of the USA!