I have a pair of 454's that currently have steel mesh flame arrestors on them. I am thinking of going to a K&N arrestor- say the 9x3 size. My vavle cover breathers are currently vented to the flame arrestors with hoses. Has anyone had any adverse results - i.e., blowing up : ) -by using the shielded K&N or other brand push-in valve cover breathers? I note a lot of HP motor builders use the push-in breathers, however, I have been cautioned about using them on a boat. Thoughts?

I have used the K&N caps your are talking about on 900hp motors with no prblems at all. We did however put them on a threaded tube to thread into the valve cover to give the cap some ht above oil splash etc... from valve train.

i'm running them on a 550hp blower motor no probs so far.

K&N makes adapters for the vent hose your talking about. That way you can retain your original setup .
They also make one for the fuel pump overflow line.

what dia. is the extension tube you used on your 900's. ( dia into valve cover ) i need to use something larger on my 540's. im getting to much crank case pressure,and oil is blowing out my intakes in the front & back.

Sure you don't have excessive blow by I had the same thing with a 540 Ford. After some investigating I found 50 lbs comp. in #1 cylinder(2 thru 8 were 180). The rest was hitting the crankcase