unfortunately with the edelbrock carb you can't remove the secondary powervalve. one of the things I dont like with the edelbrock is that it is a vacumm secondary but there is no real way to adjust the opening rate of the secondary. I agree with Thunder that the 750DP would be way better. on a side note, years ago we had a problem with one of the modified boats running out of fuel in calm water running flat out. turned out that it was the scoops. they were open front and rear and the flame arrester was up in the scoop. the air flow thru the scoop was pulling fuel up and out of the vent tubes as it went past.

I have had a lot of past trouble with Holley power valves. I know the trick of puting a ball bearing in the drilled out passage to act as a check valve to protect it in the case of a backfirebut they still seem to have more trouble. A good working injection system would be best though you can destroy an engine in the tuning process. The AFB style carbs had perfect air/fuel ratios for blown engines through out the Dyno testing though none of the dyno pulls lasted much more than 10 seconds or so full throttle at full load. I think float drop may be the issue they were set at 15/16" as was recomended further down on the same instruction page it says all Edelbrock/AFB carbs float drop settings should be 1 1/4 ??? were my needle valves not all the way open? I just set them at 7/16 l 1 1/4 and see if that helps.

Checked the tank vent, good idea, but it checked out fine, a good 1" hose no crimps. wish it was that easy.

Edelbrocks have mechanical secondarys and no power valves

There's about a couple thousand of us on oso running holleys on top of roots blowers in offshore boats, and very few running carter or edelbrocks .

I personally been running holley carbs for many years. I think maybe once, I had a leaking powervalve. Some say backfires can take out the pv on a Holley, Holley says not on any carb built after 1991. My goal though, is to not have my engines backfire.

but according to one self professed expert on here, backfires or normal and all of them do it.