My recommendation is to try what u have, and see what the results are (pump). Replace spring as soon as u get the pop off.
Make sure it will pull a vacuum at idle while engine is warm, prior to doing you dyno pulls (if u run it sealed).
Hope this helps
Mark
Mark what you are saying is the pop off doesn't react quick enough for pressure spikes?
I am intending on running a Peterson inline Pop off from my fuel pump plate, I assume Peterson have gone a little heavy in the return spring so the valve seals in most situations so its a matter of me finding a light spring to hold the valve in place.
My Nascar Ford valve covers have a pop off valve welded on approx 3/8" ID I was going to weld a -12 boss fitting there and use a breather for road, and cap it for race use.
