I am looking for some guidance on HP bodied Holleys. I would like to run the largest vacuum secondary carb that I can on a 489 BBC build. This is a street car, 10.1, medium cam, 781 heads with large valves. I thought I saw on the internet that Holley used to make an HP body 950 or 1000 vacuum secondary carb. Can anyone confirm this or know the carb number to look for? Another thought is modifying and 850 VS carb, such as the one that comes with the ZZ502 engines. Is there a HP main body that would convert the 850 to an HP and retain the VS? I know the older 3 barrel carbs are VS, but do not know much about them either. Thanks for any information.
Never heard of 950 hp with vacuum secondary's. I have the double pumper version which is model 80496. It's a great race carb but terribly rich at off idle and light cruise. My wideband says 11.0 to 11.5 which is way to rich for a light cruise. In a drag race situation it's right on the money at around 12.5- 12.8. Not worth the changing fouled plugs and single digit fuel mileage. Swapping my little 750 Quick fuel back on. This is on a 512 BBF, built much the same as your Chevy.
On back to back runs with the Holley 950 hp vs the Quick fuel 750 q series was about a tenth with the Holley slightly edging the QF carb. Not worth the 30% worse fuel mileage and burn your eyes rich for me keeping the Holley on.
I was thinking the VS would be a little easier to tune for the street as well as fuel consumption. I wasn’t sure if the 750 would be enough carb, but for 90% street driving it probably would be ok. There is a big swap meet coming up the following weekend and I was going to be on the hunt for a carb.
The carb will provide only enough air-fuel mix that the engine wants. If it's properly adjusted the engine will not bog down. I ran a Holly 3 barrel on the street on a damned hot 383 Dodge for 3 years and it worked like a charm.
Proform and Quick Fuel make a vacuum secondary 750 main body kits that flow more , they are made like a race carburetor with out a choke. So if you find a list #3310 750 Holley (cheap) at the swap meet you may want to consider it, I have run low 11s with the Proform conversion bracket racing. Proform part #67101c main body kit Quick Fuel part #6-750 VQF Have not run the vacuum secondary Quick Fuel but have changed a Holley 850 double pump to 1050 with a Quick Fuel main body kit, the quality seemed a little better. Yes, if I ever find a 950 V/S Holley (cheap) would love to try it. Norb
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