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Author Topic:   holley 4412
posted January 02, 2004 07:43 PM
i have would like someone to tell me what would be the jet size for a holley 4412 carb running alcohol.It is on a 350 engine in a modified.It currently has #77 but i think those are too small.I am getting sonme hesitation.

[This message has been edited by modified16 (edited January 02, 2004).]

posted January 02, 2004 08:18 PM
You cannot just change the jets to convert a carb (any carb) to properly run on alcohol. There are many other modifications needed.
Typically, the entire metering block gets machined internally, boosters are changed, squirters are changed, air bleeds are changed, the accelerator pump system needs changing, extra large steel needle/seats are used, and alcohol-compatible parts are used throughout the carb.
You will probably lean out and melt down your motor if you do not adequately supply the volume of fuel needed for alky, as well as meter it properly thru the carb.
I would recommend having the carb professionally modified in order to save you time and lots of money in engine problems down the road.

Hope that helps,
Dayton Umholtz, co-owner
Kinetic Performance

ps.- For starters 77 jets are gas-sized jets. Our alcohol 2bbls with proper mod's are running jets in the 130's....

posted January 02, 2004 09:33 PM
thanks a whole lot for the info. I bought this car and i think i was riped off on the carb.I suspect the seller switched the carb without me knowing.

posted January 02, 2004 09:44 PM
Unfortunately, you'll find that carb builders (or any racing business) will not send you "free" stuff to try out and compare to what someone else built. If we did that for all the racers who've "pitched" us that offer, we'd have been out of business in a matter of weeks.
It just doesn't work that way, I'm afraid.
We'd be happy to build a carb that easily works as well or better than any other builder's, BLP included. The point is, it usually isn't a matter of WHO built the carb, it's a matter of the carb builder having matched that carb to the engine application's specific needs, and the end user being able to work with the product and diagnose the entire system. This is not to say you don't have that ability (because I'm sure you do).
But like you said, many racer's problems with a carb can turn out to be the manifestation of other problems in the system.

Our 4412 alky carbs do NOT have holes drilled in the metering blocks above the jets. That method is the old way things were done when the only jets available were the standard 1/4x32 thread Holley gas jets.
Nowadays, builders are using 5/16x32 thread alcohol jets that are sized such that no auxiliary holes are needed, and they are installed in the HP-style metering blocks with a LOT of custom machining done.
Wet flowbench work is then utilized to tailor the fuel curve to the specific application at hand.
That in itself is what sets Kinetic Performance apart from others - we build EACH carb one at a time specifically for the engine in question. I personally work with EACH customer's needs until they are pleased with the performance, and do NOT just tell them "Oh well, perhaps buy another carb from us and maybe it'll work...".

Hope this helps, and good luck racing.

Dayton Umholtz, co-owner
Kinetic Performance

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