Carburetor Question

[racephotoman]

I utilizing a Edelbrock 650 on my 347 Stroker (425+HP). Most I talked to said to upgrade to an 770-850 (basically that the engine is looking for more gas). I get a little hesitation especially at low RPM range, and also when cruising on the expressway (2000-2500 RPM) and lift and apply gas again. Did go through the Edelbrock manual changing the "cruise" and "power" range meters three times - help, but still a minor hick cup. I haven't increased the jets yet, but see no great instruction how to in the manual - assuming I need to remove the carb top. I also moved the linkage to also feed more fuel to the engine.

Walter

[mikey likes it!]

I had a similar problem with the Edelbrock carburetor in my boat. After contacting Edelbrock Tech, problems were solved. I say you need different size metering rods. The number is on their website.

[christenfreedman]

Before you run out and buy a new carb I think you may just need some tuning...I don't think a larger carb will necessarily fix your issue... You will also want to provide more information about your engine with cam info, heads and intake..

[Norm B]

You might need a combination of metering rods, jets and step up springs to set the carb up. Do you have the manual for your carb? I have one but it doesn't have any info for a 650 cfm carb (has charts and tables for 500, 600, 750 and 800 cfm).
My best guess from the condition your describing is you need a stronger set of step up springs to start with. Have you checked your manifold vacuum at idle and wide open throttle?

Good Luck
Norm

[R. Button]

I had a similar issue after reworking the carb a number of times I finally tracked it down to the timing. Seems in my case having a light car, with 3.27 rear end gears I needed the timing to come in sooner, so I tried out a ford distributer recurve kit and with lighter springs my low end hesitation was gone. Not sure if it's the same issue but I tried all kinds of stuff on my carb till I made the change to the distributer. I have a stock Ford 1985 distributer on my 347 with the Ford Duraspark box. Not sure if this will help but solved my issues.

[bucketlist]

sounds like could be float level, while your at it check fuel pressure between 4 1/2 to 6 lbs, those carbs do not like excessive fuel pressure!

doing the rods and springs does not require taking the whole carb apart, 2 small access tabs on the top of carb.
need a tune kit and chart, which you can download from eldelbrock site

if it is a stumble when accelerating hard, adjusting the squirt lever up one hole helps.

[BEAR-AvHistory]

A bigger carb will most likely add some bogging to the bottom end. If you are running to 6500rpm a 650cfm carb has about 100cfm overhead before it becomes restrictive. More RPM will cut into that overhead. Is it a vacuum secondary or manual carb? Looks like the suggestions above are whack a mole & any one could be the solution.

Why not get a recommendation from Edelbrock to give you their best estimate on specific internal parts you need for your application? Buy the parts & rebuild the carb. These carbs are very easy to overhaul.

[Mesa Mike]

I think the 650 may be a little small for your setup. If you do decide to go with a new carb be sure to contact "pro systems". They build custom carbs to match your engine, trans, rear end, tire/wheel set up.

[racephotoman]

I added the strongest spring in the tune kit (according to Edelbrock) and will see how that goes this week. Next step to increase the jet size according to the chart as well. Thanks all for help so far!

Walter

[Norm B]

How did it go? Had to lean mine out due to elevation. 3500 feet ASL here. Had a little hesitation with gradual throttle application. Ran good in all other aspects. Strongest step up spring helped a little. Moved accelerator pump linkage to the hole closest to the carb. Hesitation is gone. Car goes like a scalded cat.

Hope this helps
Norm

[skullandbones]

Hi Walter,

It isn't that the 650 won't work on your engine, it's just that it is a little under the carb calculator for a 347 so you won't be in the center of the sweet spot for that carb. I think you need at least a 680 to 700. Mesa Mike is right. For your application with that much hp, you will need it to be a little larger but probably not what your friends suggested. You want to be in the center of the "sweet spot" of the carb so you will have room to move up or down for jets and such and still be able to meet the performance needs. If you get your carb from a company that tunes for your application, you will be far ahead of the curve, IMO.

Good luck,

WEK.