Alright, I am sure this has been asked many times before, but its a hard thing to punch into the search function.

what exactly is the difference b/w the 340 and 440 carbs?
I mean they are both 2300 series.
Is it just jet sizes, power valve, accelerator pump differences? Are the air bleeds and venturis different sizes?
Or is there more too it?
Thanks.

I think it's jets and the numbers on the carbs.

The numbers for sure are different and there are date codes on them if you looking for correct vintage carbs they would have to be right for your year of car. Also the venturi's or throats are bigger and there are probably more things different. I had 440 carbs on a 340 and they worked fine, it probably would work the other way as well.

Thanks, anyone else?

anyone have specs differenceds b/w them? Or have a link where I can find them? The Holley site just has the 2300.

Air bleeds, and venturi size are different, between the 340/440 carbs,....as are obviously numbers, venting etc,....and a few CFM differences between AT/MT 340/440's.......if you don't care about the "numbers" thing,.....340 end Carbs on a 440 will react faster to opening, regardless of spring tuning, vs the same spring tuned 440 end carb because of venturi/ orifice size

Small block outboard carbs have a tab on one of the booster venturis to correct a distribution problem in the manifod. Quick fuel modified my 440 carbs for use on my 416 stroker small block. I think they put a notch in the booster venturi to corect the manifold issue.

Thanks alot for the replies guys. Good info.

What I am trying to do is take the six pack setup that was on my 383 and convert it to the my 451.

The carbs are the 340 carbs that were actually built for a mild 400. The guy I bought the setup from didnt install it or run any gas thru the carbs as he ended up selling the car for financial reasons. I do not know the sizes of the jets, pv, etc. cuz when I bought it, I threw it right on my mild 383 and it worked perfectly.

Now that I am going to the 451, I think that I will have to tinker around with some things to get them to work right. What do you think?

Get the adjustable jet plates for the outboard carbs and play around with the center carb jets and PV as needed.You should get it to work with out sending them off to a carb shop

Are you talking about those jet plates they sell at Promax?
This might be a dumb question but do I need adjustable plates? Are they nonadjustable in stock form?

Call this guy and ask any questions you have. He has a ad on Racingjunk.com right now, just go to that site, and type in 6-pack in the search window. He's out of Connersville, Indiana, close to Indy.

"I have been rebuilding six packs for over 30 years. I will build your six pack to fit your needs. You tell me your needs and I will jet and build to your specs! $350.00 + shipping. This price includes (3) carb kits and labor rebuilding your (3) carbs! Jet plates and secondary diaphragms and metering blocks and main metering jets, and custom machine work is extra charge. Feel free to email me at philliprfish@yahoo.com or phone me from 9:00 am until 5:30 pm Monday-Friday 1-(765)825-6607. I am 75 miles east of Indy. All work is guaranteed and if needed I will help over the phone. I will send detailed step by step instructions so you can do the final tune! I also carry Mopar used and NOS parts. Please visit me at my web site. http://rain.prohosting.com/motrefok/
Seller Phone Number: (765) 825-6607 "