I mounted a Z-Head on my rebuilt short block a month ago. My rebuild consisted of new pistons and bores, and a new valvetrain with the exception of cam.
In my 50F degree garage even with 5W-30 and a quart of Mercon, this thing is difficult to crank particularly when warm. The engine is running cool enough where it will go an hour with no sign of boiling. I've yet to drive it because I don't want to give the car a Michigan salt bath.
So this makes me wonder if all this hand cranking effort is due to the Z-head. If you're running a Z-head, do you also have an electric starter? Do any of you crank them by hand?
Tom, I have a z-head on my stock 14, and it cranks up just fine... but I've not tried to start it in this cold weather.
Tom -- It's not much more difficult to hand crank an engine with a high-compression head than it is to crank one with a stock head. There is some difference, but it's not a big deal. I suspect that your difficulty is due to your engine's being new, especially since you have noted that it's harder to crank when it's warm.
Tom, My 23 touring cranks fine even in the winter with the Z head. It starts with the starter, but I usually hand crank it. It's only a little harder to crank than the stock head. I suspect you're still a bit tight.
I have a Z head on my 26 Coupe. When I first rebuilt the engine there was to much drag to start the car with the crank. Now that the motor is broken in I can start it with the hand crank and usually do. My wife thinks I am crazy for not using the starter.
We rebuilt our 13 last summer, and it starts fine (new Z head). At first it was a tougher pull, but soon the engine "broke" in, and it starts fine.
We started this winter under 6 degrees, by hand, with no problem. I have switched all our cars to synthetic, and they all seem to hand crank easier (don't want to start a contest).
Thanks Everyone, The Z-Head will stay on this car and I'll drive it as soon as things warm up. I'll just have to keep running it till it loosens a bit.