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info on speed demon carbs
is a 650 cfm, vacuum secondary, electric choke, Speed Demon series, carburetor too much for a near stock 302 that im converting from EFI to carb.
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I think it will be ok. Is the car a munual shift? When installed,take the car to a chassis dyno with a wide band fuel mixture sensor, to be sure. Hope this helps.
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Rob, the beauty of getting a BG carb is that you call the tech dept. and give them the stats on your car. They will want to know compression ratio, cam profile, CID, intake and heads, transmission type, rear end gearing etc. They will configure the appropriate carb based on that.
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Rob,
I second what Tony said. Call 706-864-8544 and get the tech line. They will configure a carb to your specs. Know your gear ratio, cam profile, intake type, etc. and they will tell you what you need. |
the reason i ask is i found a good deal on a used 650
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Don't buy what you don't want just because it's cheap.
I have a Mighty Demon 750 double pumper on my 428 - used to have vacume Holley |
A relatively stock 302--about a 600cfm is max--I have a 289 hi-po, mild cam, rebuilt heads, and my 600 Holley on an Edlebrock performer manifold, even being re-jetted and power valved, still seems to run a bit rich--performs well but I'm always having to blip the throttle to clear it before I take off from a stop--now it may not be tweaked just right either--
Don't Buy something that will cause you grief just 'cuz the price is right--been there done that, more dollars wasted to save a few $$. Just a FWIW. |
This direct from the Holley site.
How To Calculate CFM: Engine size (CID) x maximum RPM / 3456 = CFM CFM @ 100% volumetric efficiency (Example: 350 CID x 6000 RPM = 2,100,000 / 3456 = 608 CFM) Approximately 608 CFM would be required for this engine. However, most Street engines are capable of achieving only about 80% VE; a modified street engine with ported heads, headers, intake and carburetor can achieve about 85% VE; a fully modified race engine can achieve 95% or greater VE. The CFM number arrived at with this formula must be factored by this percentage. As can be seen in the above Holley information, it doesn't take near as much carb as you think. Actually, if you run out the formula for a 289 or 302, you'll find that 500CFM is a lot closer to what will really work right with a mild engine. I tried the big carb(600CFM) trick on my '64 El Camino with stock 283. It didn't like it at all. Nail the gas at under 3000RPM and it just bogged. Get some compression (11:1) stiff cam (.550@.050" 108 degree lobe centers) low butt gears (3.73:1) do the head work and a 600 or 650 will probably do a decent job on a 302. I will add the Holley part to the new FAQ forum Brent and Ron are starting. Al |
wow thanks for the info. thats exactly what i was looking for.
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I ran a Holley #1850 600CFM Vac Sec "Emissions" carb on a mild 302 motor, and it ran great.
Don't knee jerk, read a few posts, and trashcan the Holley for a Demon, or trashcan the EFI for a carb. Most FFR builders retain the stock EFI. |
CARB SIZE
Prestage.com Home Page > Car Math > Engine Building Calculators > Calculate Carb Size
GO TO THIS SITE AND CALCULATE IT FOR YOURSELF. http://www.prestage.com/Car+Math/Eng.../default.aspx:) |
Tony is absolutely correct.....let the pros pick the correct carb for your application.
You can visit my tech articles and read more about Demon carbs at www.4secondsflat.com I you still have questions about what carb you need then call the BG Tech line or myself and we'll select the correct one for your application. Don |
Don-
Good to see you over here. I just bolted up that Mighty Demon 750 and new fuel pump that you sent me last week. I dropped the power valve to a 3.5 and just bolted it on. Wow, out of the box, big difference compared to the Holley that I was running. I think I'm going to head to a chassis dyno to get it set up perfectly, but already it is much better. But you may be getting some more calls from me:) Thanks for all your help. (Just don't let these guys know you are a mopar guy;)) Mike * BTW, Don really does have a great website with a lot of good info on it, it is worth a read. |
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