Free Holley 750 Vacuum Secondaries !!!

Sterling · 02-22-2009, 01:52 PM

Well, it's really not worth the effort. You're better off using the Nikki and tapping out the secondaries to turn them on a lathe.
I use 16* & 7* for inlet & outlet angles, respectively. Ideally, the inside diameter of the venturi at it's smallest should be 1/2 the outside diameter. With those angles & relative measurements, the venturi should be very close to 100% efficient. (proabably closer to 97%).
But your 750 is simply too huge. Even if you insert small primary venturis, the rest of the mods you'll need to get it to work basically amounts to re-engineering the entire half of the carburetor.
It's a very difficult task for no gain what so ever over a Nikki you could spend 1/50th the time modifying. Not only that, but mod the Nikki emulsion tubes to take Holley jets, and there's simply not a more tunable carb on the market for the 12a.
If I were you, I would put the effort into modding a Nikki, and then making that work with a RB holley manifold.
NOW you're talking!

If you were doing this with a RB prepped Holley 465, I'd say "go for it!". Giving some low end response to that package (carb + the beatiful manifold) would make it the top performance carb choice for the 12a-anyport, IMO.

The primary Nikki venturis measures 20mm inside diameter. I cut mine to 22mm, though it's not necessary for a stock/streetport 12a. I just do it to make the Sterling flow 465 cfm, else most folks won't even give it a second consideration.

02-22-2009, 01:52 PM	#2
Sterling Premium Vendor Join Date: Feb 2008 Posts: 74 Rep Power: 18	Well, it's really not worth the effort. You're better off using the Nikki and tapping out the secondaries to turn them on a lathe. I use 16* & 7* for inlet & outlet angles, respectively. Ideally, the inside diameter of the venturi at it's smallest should be 1/2 the outside diameter. With those angles & relative measurements, the venturi should be very close to 100% efficient. (proabably closer to 97%). But your 750 is simply too huge. Even if you insert small primary venturis, the rest of the mods you'll need to get it to work basically amounts to re-engineering the entire half of the carburetor. It's a very difficult task for no gain what so ever over a Nikki you could spend 1/50th the time modifying. Not only that, but mod the Nikki emulsion tubes to take Holley jets, and there's simply not a more tunable carb on the market for the 12a. If I were you, I would put the effort into modding a Nikki, and then making that work with a RB holley manifold. NOW you're talking! If you were doing this with a RB prepped Holley 465, I'd say "go for it!". Giving some low end response to that package (carb + the beatiful manifold) would make it the top performance carb choice for the 12a-anyport, IMO. The primary Nikki venturis measures 20mm inside diameter. I cut mine to 22mm, though it's not necessary for a stock/streetport 12a. I just do it to make the Sterling flow 465 cfm, else most folks won't even give it a second consideration.