Purchased this P car in January. It was equipted with a vanilla Holley 600 with vacuum secondaries. Although it ran pretty well, it leaked at the front bowl gasket, I figured that if I was going to pull it off to replace the bowl and metering block gaskets, it was a perfect time to try something better. Purchased a new Holley 750 4150 DP model 82751, a factory 'tuned' carb with no choke, milled air horn, 4 corner idle circuit, screw in air bleeds, etc. Another plus, the carb is wet flowed at Holley, so be careful when you remove it from the box and turn it over, some solvent will leak out, and the accelerator pumps will probably have solvent in them. At it's price point, has to be one of the better deals out there. Since it's rained for the past 3 days, I decided to swap them out. Pulled off the old carb and took a good look around. First thing I noticed was a missing rubber nipple on the fitting that screws into the front of the intake for the power brake hose. Along with the large nipple, there was a very small nipple (right size for distributor's vacuum advance) missing, resulting is a small vacuum leak. That probably explained the rather lazy return to idle when blipping the throttle and slight stumble off idle. I capped it, installed the new phenolic 1/2" 4 hole spacer, new gaskets, and 750. In retrospect, it would be nice to buy the replacement front bowl and tranfer tube to allow the fuel to enter only the front bowl left side, then transfer to the rear bowl via the transfer tube on the right side like the Holley's used on the BOSS302, BOSS429s and 428 motors. With that mod, I wouldn't have the deal with the fuel hose on the right side running into the distributor cap, but perhaps that's a mod for another day. Fired it up, let it warm up, adjusted idle speed, and proceeded to go through the idle mixture adjustment. This carb was virtually dead on, I don't think that any of the 4 idle screws ended up more than 1/16 of a turn different than the factory settings, if that.. Took the car out for a quick drive in the neighborhood, dramatic different in drivability in the 5 minutes I drove it. Instant throttle response, off idle stumble completely gone. Blip the throttle in neutral, motor instantly reacts and instantly returns to idle. So far, very pleased, we'll see how it works on road.
Good luck.
http://www.holley.com/0-82751.asp
BTW, below is a link to a '69 BOSS429 Holley on Ebay. 69's were unique with front bowl vent. That same basic front bowl (w/o vent) and transfer tube on the right side is available from Holley yo allow the fuel to enter the front left side, right next to the P car factory hard fuel line. BTW, if you need a correct B9 carb, here's your chance to get one at a good price..
http://cgi.ebay.com/ebaymotors/1969-Ford-Mustang-Boss-4...QQrdZ1QQcmdZViewItem.
