HG R&R check, have to warm engine?

[skid542]

This may sound noobish...

Before I put everything all back together in my engine compartment, it'd be nice to verify the heads seated well. So I was thinking if I just hook up the timing belt, put some oil into the motor, and then do a compression test.

So the question is, do I have to heat up the motor to really 'seat' the heads and verify that they will hold? I'm kinda thinking yes on account I assume there is significantly more pressure inside the cylinders under full throttle then just cranking it over. And there would be a little movement when everything is warmed up.

Is there really any way of knowing I did things properly other than going driving?

Thanks.

[evolutionmovement]

A compression test would probably not tell you if there's a problem. I personally wouldn't bother since it would only show you if there was a problem at the fire ring. Even then, it's more likely it would be telling you you have a bad valve, seat, or rings.

[Arctic Assassian]

Subarus have a funny way of fooling comp. tests. You can have a hole straight through the piston and it'll still make compression. The best test is a leakdown test, because it's just as easy to do, but gives you much more information.
Esentially you put compressed air to your cyl, and listen for air rushing through your oil filler( bad rings), or your exhaust(burnt exhaust valve) or intake( bent intake valve) or bad seals for both. You also look at your coolant to see if any bubles are coming out(headgasket). Most people just use the radiator cap, I use the highest point in the system.
As you can see, one easy test, can tell you exactly why your car runs, smells, performs... funny.