I recently picked up this cool carburetor. BUT, I have always had problems identifying the carburetor if it has a milled top like this one does. I have no idea of finding out how many CFMs this thing is, or any of the specs on it for the matter, or even if its alcohol or not? (It says ALKY everywhere). Can anybody tell me what carburetor this is and also some specs on it such as CFMs and such? Also, could somebody tell me how I go about identifying a milled top Holley? Both metering plates on this carb are stamped differently. Thanks! :evil:
Yes.....The jet sizes among other passages will give it away. Alcohol needs about 2.5 times the amount of fuel. The seats will usually be .110 dia and sometimes they change the floats to something more alcohol specific. I'm surprised it doesn't have screw in bleeds. It looks to be a 750cfm baseplate. IT might be Alcohol conversion. I'd rather it be machined specific for the type of fuel.
To identify a Holley that has had the List number milled away, in this case because it was originally stamped into the front of the choke tower, you need to measure 3 things.....Throttle blade size of the baseplate, the size of the narrowest point in the primary venturi's of the main body, and the same point in the secondary venturi's.
Once you have these three things, you can go to Holleys site, go to Tech help, then "reference documents", then "carb numerical listing" and look through the list comparing those 3 dimenrions until you find a match.
In your case, I can tell from experience(and the gap between each blade on the throttle plate) that you have 1-3/4" throttle blades, which leads to a carb 830 cfm or bigger. The next clue for me is the "4781" stamped on the front block, this was the List number that was on the front of the choke tower, "List 4781" is the number for an 850 Double Pumper. I can tell you it is at least 20 years old, as it has the old style mechanical secondary "rotary" linkage that pivots off a boss on the main body.
Beyond that, the fact that it has a custom tuners logo and name on it, you would either have to do more measuring of the calibration orifices, jetting, etc inside it or talk to the builder to know anything more exact, other than the obvious "alky" stamp in several places.
. If you need a gas carb., sell this nice carb. to someone who needs an alky carb. and buy a gas carb...
. You would have to throw most of it away to convert it for gas... which would be stupid...
. You can prolly score a nice used gas Holley for $100 - $200 at a big swap meet... with a choke tower...
. Where are you located? I've stumbled across gas Holley 850 dual feed double pumpers like new for as low as $75 at Detroit, Michigan swap meets... exotic car parts are just ordinary in that area...
.
A brand new "Boutique" 850 costs around $640.oo so use that as a guide as to buying a used carb and modifying/rebuilding it or converting your carb,etc
I wouldn't jack with a methanol carb unless you want to rum methanol. The metering blocks,air bleeds and needle&seats are all different and in some cases the booster Venturi and the passages feeding them are modified.
Sell it and get yourself a gas carb
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