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Old 12-29-2008, 11:01 AM
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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.

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Old 12-29-2008, 11:27 AM
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Quote:
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.
Ed

Last edited by kleen56; 12-29-2008 at 11:38 AM.
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Old 12-29-2008, 02:10 PM
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Joe Sherman runs 750s on his 289/302 builds approaching 400 hp with the factory iron heads. (I am just reporting it)

Proper calibration of secondaries of any carb is necessary for best performance.
Vacuum secondaries need springs adjusted, and Edelbrock Air Valves often need adjusting also.
Don't like or dislike any one type of carb based on a mismatch or mistune of one or two instances.

Me, I like the Edelbrock (AVS preferred) for 80% of the uses.
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Old 12-29-2008, 02:58 PM
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Hi-Po 289s cam from Ford with an Autolite( nice carb, but small) of about 465 cfm. Shelby used tri-y headers and a vacuum secondary 780 on his Hi-Rise( Edelbrock made, I believe).Shelby's were (the first year) just tamed race cars for the street, they ran a 3.89 gear and glasspacks with side pipes( side exiting, not traditional style sidepipes). One of my customers is an original owner of one,a lot of fun, but it was set up with the knowledge at the time and it has progressed much in the last 40+ years. You could take that same car and do some simple changes and it would be quicker than it is..with a smaller carb. Of course, that's a moot point, because he like most Shelby owners are unlikely to alter too much for fear of lost value. His in particular, because he IS the original owner and has every receipt he ever got. A side note for the Poncho fans, he had just purchased a new GTO about a week before and traded it in for the Shelby when he drove by the Ford dealer and saw it. Not many cars that generate that type of enthusiasm anymore. Wonder where that goat is??
*correction* right after I posted I realized that it wasn't a 780, it was a 715. They were the only ones that had "cathedral" bowls, the predecessor to the dual feed/center pivot style bowls.

Last edited by woodz428; 12-29-2008 at 06:13 PM.
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Old 12-29-2008, 04:12 PM
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http://www.buicks.net/shop/reference/carb_cfm.htm Check out the calculator..shows about 464 cfm at 85% VE.. the smaller carb will have a much crisper throttle response at normal driving speeds..You will not need a 650 unless you are seeing 6500RPM+ on the track..I would pick the 550 CFM as a good compromise..

Sam
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Old 12-29-2008, 07:38 PM
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moving to the engine forum.

I split off the carb discussion from the rear differential gear discussion.
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Old 01-04-2009, 07:48 PM
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The old 350hp Chevy 327 from '66-'67 was a potent little motor once it got a decent exhaust system, and it came with a 585cfm carb that seemed quite adequate.
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