More info I got from Jon.
I don't have a better ET number for you, because my partner in our GoodGuys/ Heritage Jrfuel car did not run a vacuum pump on his old engine, 406 ci all iron SBC [ non-raised runner 23°] , but when I built
my raised runner 23° all iron engine I ran the vacuum pump. Old engine ran the best of 7.36, new engine 403 ci ran the best of 6.99. 189 mph.
If you are running brackets, it's whole lot of work and effort to chase that 20hp. it works because of better ring seal, with low tension rings, plus the engine needs to be vary well sealed, a constant goal for us.
Our vacuum, measured with my RacrPak computer, ranges between 5-16" but mostly 10". The 20-25 hp claim was from comp engine builders that have dyno's. All of our alky burning JF teams run vacuum pumps , but a few also run dry sumps which give them more vacuum, 12-22". BTW with any vacuum over 20" you must increase the wrist pin clearance , because all that vacuum pulls oil away from the wrist pins. I had one SBC engine with a small hole drilled up the center of the alum rods to get oil to the wrist pins, from the rod bearings. That's one of the reasons I posted if you race brackets, it may not be worth all the work and money. Like besides getting low tension rings, O Ring groove valve cover adapters, expensive silicon seal, and use lots of it, around the intake gaskets, mag drive hole, like any gasket surface . It got even tricker with our Gene Adams built early iron Hemi because it didn't have as much vacuum as my SBC, so we put a smoke machine hooked to the oil pan and we had smoke everywhere, like around the rear main seal, because no one seems to make a double lip seal, we even had smoke comming out the exhaust bolt holes. It took us a while to figure the copper head gasket was not sealed good enough around the water holes, thats how the smoke got in the water jackets and out the zoomie bolt holes.
Like I said it's allot of work and maintance to chase after vacuum, like everytime we warm the engine up in the pits we disconnect the hose from the valve cover [ because trying to keep the wrist pins in good shape] we spray some brake clean in the pump, and aim the hose going into the puke tank into a oil drain pan, just to clean the pump, they work better when clean of oil.
I hope this helps, could you add this post to FED.org. I think this will only show up in messages.
Good Luck with your project, call if you would like more info, 805-444-4489
Jon Hansen, Hayden Wheels, and founder of Jr Fuel Dragster Association
