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.

StumpDrummer · 02-24-2009, 09:13 PM

Sterling
I ended up giving the 750 back to my instructor . It was too good of a carb to butcher if something went wrong.

Will a nikki bolt up to a common square bore flange?
If so ill probably just get one from you in the future.

I got a 390 on it now it does almost fair it pulls till about 7.5-8 k
then starts dying
the old Edelbrock 650 pulled to 11k but it died catastrophicaly
when I droped it...yep it cracked ...its easy to lose your balance on one leg in a shop

how large can you go with the secondaries on the nikki?
and how much airflow can I expect?

Im also going to be running a draw through turbo setup.
as my turbo is dying. Im gonna have got to get a new one soon!!!
I just dont know what size it will be yet, but it will be a little bigger than the old rayjay that was on it , Im wanting 18-20lbs of boost again no need for more than that. P.M. me the price so I can start saving!!

02-24-2009, 09:13 PM	#2
StumpDrummer Rotary Fan in Training Join Date: Feb 2009 Posts: 31 Rep Power: 0	Sterling I ended up giving the 750 back to my instructor . It was too good of a carb to butcher if something went wrong. Will a nikki bolt up to a common square bore flange? If so ill probably just get one from you in the future. I got a 390 on it now it does almost fair it pulls till about 7.5-8 k then starts dying the old Edelbrock 650 pulled to 11k but it died catastrophicaly when I droped it...yep it cracked ...its easy to lose your balance on one leg in a shop how large can you go with the secondaries on the nikki? and how much airflow can I expect? Im also going to be running a draw through turbo setup. as my turbo is dying. Im gonna have got to get a new one soon!!! I just dont know what size it will be yet, but it will be a little bigger than the old rayjay that was on it , Im wanting 18-20lbs of boost again no need for more than that. P.M. me the price so I can start saving!! __________________ How can we possibly know where we are going (as a people ) when we dont even know where we come from!

02-22-2009, 01:52 PM	#1
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.