If you have a factory style cross ram, it doesn't need a blow off. In fact if started correctly the Indy 440-25 doesn't need one either. Mine popped the lid once. Wasn't even a big bang. Just a poof. Once I learned how to start it, never ever another issue. It does have a pop off but has never banged it. Cold start; fill bowls with electric pump, shut pump off. Pump throttle 3 times. then let it set 30 seconds. 1 more pump, ignition on, throttle cracked slightly. It should fire up on one revolution. Warm start does not require the 3 pumps. Very cold (less than 45-50 degrees) through a cloth fender cover over the carbs then use the standard cold start procedure. My car has 700+ passes with this intake. This procedure works.
Doug