Originally posted by lluciano77
A sleeved 950? Did you adjust anything to compensate? Did you enlarge the air bleeds, PVCR restrictions, idle restrictions, change jetting, anything? If not, I can tell you right now for sure your carb isn't metering right.
Vacuum secondaries? I know what they knew. They knew if people had a carb that was too big, it would be a lot more forgiving with a vac. secondary. You get better customer response, and can sell a lot more carbs that way. I'm not saying they don't have their place. I have one on my SBC 400 right now.
That's bad news! I have only gotten 15 years of trouble free daily driving out of this setup @ 15mpg. I was hoping for 30 years but I guess it will blow up B4 then?
Of course I changed the metering with the new barrels, like I said these carbs are great if tuned properly. I set up all my custom carb installations w/ an Edelbrock O2 sensor so they are optimal at all driving conditions.
And the 950 and 1050 Holley 3-bbls were designed for NASCAR, not the street market. You had to special order one and the box said "not for street use". And they came race ready as vacuum secondaries. They were never made as mechanical secondaries. Couldn't have been too bad, NASCAR banned them after less than 2 seasons for being too good!
Again, I have seen and installed many dual 390s on medium sized engines and they work marvelously if tuned properly. They are no different than 650s or 750s etc. as far as metering tuning goes. Jet, secondary spring, power valve, and accelerator pump them correctly and they purr! And some of the cars can lift the front wheels too. One thing they do provide is better off idle response which is preferable for the street. For sure if you want WOT performance at the drag strip @ 8,000rpm, go for the 750 or 850.