Originally Posted by woodz428
Just some input, and you'll get others that will readily disagree...but having built Ford exclusively for 40+ years and many of the early ones being 289s, I think the 650DP is too much carb. A 600 vacuum secondary would be about the largest I would suggest, probably the ideal one actually. I think the 3.50 gear has just compensated for the carb being wrong for your application. A double pumper is really more for a manual or comp type application. You'll also get a better performing engine, I think that bog you referred to initially was from too much fuel when you kicked in the secondaries and the extra fuel.
The #1 biggest mistake made by rodders is TOO BIG a carb...I think you are there.That's not an opinion...it's been found over and over. Your 289 would need a lot of rpm to even flow the 600cfm, the extra cfm and the extra accelerater pump is overkill. I ran a 660DP on a Cleveland(351) with a 4 speed in a '70 Mach I with 3.50 gears and it was too much for a mild Cleveland. Now it did seem to pull well at the upper rpm range...but really...who wants to always be in the upper rpm range regularly, not me.Most driving is done below 4-4500 rpm, the other rpm is under "special" circumstances.
Woodz- I agree with you! Originally, I ran a Edelbrock 600 CFM carb on my 289. It ran as if I had a 2 barrel sitting on the manifold. Back in the days, I had a 351 Windsor in a 66 Mustang and ran a 600 cfm DP Holley which made that car come unglued. I got the 650DP for free from a friend of mine. Initially, it was running extremely rich and the bog was there whenever I depressed the pedal suggesting way too big of carb. The floats were set way too high on the carb and I dropped the jetting down two numbers which leaned it out quit a bit. I'm currently running 69- 351W heads which have been ported as well on my 289 (may change that to aluminum aftermarket heads soon). The carb is running excellent right now, plugs are running light tan color. The only hesitation I get is when the secondaries kick open, but then it pulls extremely hard. I've ran several vacuum secondary carbs and they simply just don't do what the double pumper carbs do as far as pants in the seat performance. I've been told the 650 is way too large of a carb by several other people as well and it may be. If I recall, didn't Shelby's run the 650 dp on their Hipo 289's? I've been told that 289's run best with 500 cfm carbs, and 600 cfm at the max, your info is correct. With the 2.75 gearing, the carb seemed to be too large. With the 3.5's back in, it's been a blast driving and the performance with this carb has been great. My mileage stinks!!!
I won't go back to the Edelbrock carb or the 2.75 gearing, but would like to try a 600 cfm DP to see if there is a difference performance wise. Thanks for your info and help also, Woodz.