See, but ,you said it was not smoking blue; I assume you meant out the tailpipes. which if you had a valley leak, it would be pouring smoke.
But there is an easy test for this. Just pop the PCV out of the grommet,flip it out of the way, then plug the hole. Make sure the dipstick is seated. Remove the breather and put your hand, or thumb if it's big enough, over the hole in the VC, to seal it. Rev the engine up to about 1200 to 1500.
Wait a few seconds and if the valley is leaking, it will suck your hand onto the breather hole.
On the other hand if you have pressure there at 1200 to 1500, depending on the severity, you could be having a mechanical problem; new test required.
Another thing you can do is put a vacuum gauge on the dipstick tube, and plug both breather holes; but if you have pressure there, do not let it rise above 4psi, or it might blow a seal out, and it would really suck if the rear cam plug popped out......... better make it 3psi max, cuz I didn't install that plug.
As for the 750DP and AirGap, I run that on my 360/4-speed, and it is definitely not too big. I can idle that sucker down to 550 rpm @5* advance,with a
[email protected] cam, and she will pull herself around the flat,hard level, parking lot at 4 mph (3.09x3.55=10.97 starter gear). And she'll power away with no hiccups.
Edit; sorry; may not be a fair comparison, as I have about 180psi cranking cylinder pressure.