Anyone Running A Holley 650 Dp?

It's kinda weird to me that carburetors are becoming a mystery as opposed to F.I.. It wasn't that long ago, when aftermarket FI setups started to hit the market that it was the other way around. Probably the biggest misconception that I see everyday is people over carbureting their engines, then bit ching because a similarly modded F.I. system was "so much easier" to drive, was more reliable, and performed better, all while getting better fuel economy than the carb'd version did. For me having stood across the speed parts counter on the selling side, carburetor recommendation was always "smaller is better". a 650 DP is a mild 351 or,at the very least, a street/strip 302 carburetor. There is a 600 DP (4776) or a buttload of vacuum secondary offerings out there that would probably perform better than a 650 DP on Opies' engine.

I mean, this ain't coming from me,.....all anyone has to do looking for advice on carburetor sizing is to poke around Holley's web site, and the formula for carb size has the above engine example over carbureted even at 600 CFM.

I'm with Ratio411 on this one, a 570 vacuum secondary carb would probably be more than adequate on the Opes' engine.

I know my engine is a completely different example,....but even at 600 cfm on a stage 2 headed, GAYGE 1 cammed 281,..had me cutting back on the jet sizes 10 steps to get it where it wasn't running fat at W/O throttle.

Gotta realize that the 302 (289 even more so) has a very short stroke and relatively large bore.
They are a natural to make power at high rpm. Why not play to your strength?

As for the T289 vs the T302, the 289 is far away a better intake.
The T302 has a larger plenum, narrower and shorter runners, and was 'squished' down for hood clearance.
The 289 has smaller runners than a Vic of course, but that is one reason it has a better low end.
It'll still scream, and there was an article in Super Ford long ago, that you can still find online that gives you tips on adding significant HP to the T289 with some mods that can be done quickly, added to a port match.

I know there are lots of intake choices, I am just letting folks know the T289 is one of the good ones if you don't NEED a Vic.
Edelbrock only stopped making the T289 to save money, it was a complex casting...

Not wanting to get involved with the debate but... I'm using a vacuum secondary dual feed Holley. 80670. Seems to be best of both worlds. Car starts up easy, doesn't bog, and has a great feel. It sits on a 331 with trickflow heads, and a mild. 498 cam

madmike1157 said:

Probably the biggest misconception that I see everyday is people over carbureting their engines

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I see this all the time. Even experienced it myself. Had a 650 vacuum secondary Edelbrock carb on a mild 351 - ran awesome. My dad said to me "son, I'm gonna stick this 750 Holley on your truck and it'll run awesome!" so of course 16 year old me said "oh hell yeah!". It ran like complete crap. Stepped back down to a 650 Edelbrock and I'm never looking back.

Well, i thought i understood the whole overcarb thing, until i got my Pro Systems carb. I went from a 650 Holley, which ran awesome on my 347, to a true 780cfm carb that runs even better...Soooo i don't really buy into that whole carb size calculation crap anymore. My 650 was tuned on a dyno, and this 780 hasn't been on the dyno, so i know it wasn't something wrong with how the 650 tuned. Maybe it's the single plane, maybe it's the cam...all i know is the car runs like stink and i'm not complaining.

V.E. changes the carb formula. On a race engine w/ a really good V.E. of 100 or so, the cfm thing goes up significantly .