1974 4.1L inline six

[LTJGWorth]

I've got a 1974 boat with an 165hp GM inline 6. The motor is almost exactly the same thing that those old Chevy and GMC pickups used to have in them. So I figure maybe I can get some answers here. The engine sat for a while before I started it last summer, and it ran great (it always has) when I started it. I winterized the boat this past winter, and just recently decided to get it out and tinker with it, as I plan to remove the engine and place it in another boat and throw this old one away. I charged up the battery and got the engine to turn over a few times before the starter went out. I changed the starter and it would turn over great and fire, but wouldn't start. Poured some gas into the carb, got it running for about 10 seconds, and it died. Tried again, wouldn't start. Cleaned the carb a little bit, wouldn't start. Thought I should change the plugs (they were really, REALLY old) and I got them all out, but one which broke off in the wierdest way I've ever seen one break off into the head. So I had to take the head off to get what was left of the plug out. I take the exhaust/intake manifold off, remove the head, get the plug out, replace the head with a brand new gasket, replace the exhaust/intake with a brand new gasket, and try to start the engine. I get no compression. I retorque the head bolts, and I get compression in one of the cylinders I test (with my finger). I put the valve cover back on and try to start it. No compression. I retorque again, no compression. I pour a little oil down in each cylinder to lube and seal things up a bit, no compression. I'm stumped. I had compression before the engine was taken apart, now I have none. What could it be?

[MagicRat]

My guess is that you have over tightened the rocker arms to the valves do not close properly.

If you did not touch the rocker arms at all, perhaps you have mixed up the push rods or the new head gasket is thinner than the old one.

If ths engine has hydraulic lifters (it should), loosen up the rocker arms a bit, then slowly tighten the arms while rotating the pushrod with your thumb and index finger. When you feel a slight drag on the pushrod, rotate the rocker arm nut exactly 3/4 turn. This pre loads the lifter. Do this only on the base circle of the cam, when the valve is supposed to be closed.

This procedure is for the small block V8, but my Haynes manual says it is the same for the six.