Also, if I remember properly, engine should be warm (at least). Compression losses can be higher when cold, but the engine is going to run hot anyway .
In a warm engine valves are going to open sooner too (metal rod expansion). Don't know how much difference that can cause.

And after checking some old threads...

http://slantsix.org/forum/viewtopic.php ... test#35932

you should remove the air filter. I'll check that in the service manual when at home.

_________________
/6 Dodge Charger 69
...there's nothing like using the "Search" link above to solve most of your problems...