I currently have a 73 Barracuda 318 (mild build) that currently has a Street Dominator manifold with a older Holly 6R-5643B and a 7956 throttle body. All of the original pollution stuff is still on the car and good shape except the vacuum line could be replaced. The car has developed some surging at cruising speed which I believe is a vacuum leak somewhere. A coupe of questions: 1. What carb do you guys recommend? 2. Can / shall I use the original throttle body with the new carb or replace it? 3. Would you recommend removing the pollution control stuff?

Thank you.

Eddy 1406. just need the flat plate to convert the spreadbore intake flange to square bore (dirt cheap) & a strip kit for the carb. You can toss the emissions stuff & run the dist directly to ported & rework the dist adv systems.

Do yourself a favor and buy a Holley Street Demon 625cfm. It has the most modern metering circuits and will bolt to either squarebore or spreadbore intakes. Get the one with the space age plastic bowl, will keep the fuel cooler.

The numbers you gave us do not say much about the carb you currently have. The number that really matters is stamped into the front of the airhorn/choke tower. It will be something like "LIST 1850-6"
The next row down is the Holley date code. It isn't really important as the list number tells all.
Sometimes the word "list" is replaced by a capitol "R".

If it is a Ford carb it will have the ford part number, if it is a chevy carb it will have a chevy part number, both usually have some more Holley numbers, sometimes list and sometimes not.

Everything about the carb can be found in the Holley Carb Numerical Index. EXCEPT I recently looked at the numerical Index on the Holley site and found that they are leaving out part numbers for items they don't currently sell. We are lucky that there are still copies of earlier numerical Listings available on the internet. For example, at one point in the '70s Holley began to sell carbs that were emissions legal. These carbs used Holley higher precision jets, recognized by three digits. An example would be a jet marked 602. It's a close tolerance 60 jet.
The old Numerical Listing contained the number for the jet for a particular carb. The new Numerical Listing has "NS" in that spot. If you have a box of jets and are trying to sort out the ones for your particular 6619 or 6919 or other emissions carbs, you cannot using the new Numerical Listing.

May mean little to some of you, it means a lot to me.

R.

Heh. If want to buy a new carb, a phenolic body Street Demon is certainly one to consider.

As far as the one you have, look at the airhorn as dogdays posted. That should have the List number. If not, post a photo.

Slight surging at cruise is likely lean as you suspect. However a vacuum leak more likely will show itself at low load (like idle). So the next question is whether it happens only at high speed cruise (60 - 70 mph or up) or also at city and country cruise, 25 mph and 50 mph respectively? This will help identify the circuit supplying fuel when it seems to go lean.

Finally, how old is the fuel? If it has winter fuel it will often act lean in hot weather. Winter fuels have higher allowable RVP and more light end components. This saves Joe consumer money and makes sure Jane's car starts more easily in the cold. However, the same fuel evaporates too easily on a hot day. Worse case result is vapor lock, but even when fuel is making to the bowl it can seem like its lean, because in a way it is.

I overlooked the obvious like Mattax said, lets find/fix the lean then you'll be in a much better position to decide if you want to go to the time/expense of a carb swap. A lo po DD 318, you may want to leave it as is (when fixed). You said it recently developed? any changes preceding this?

that's good info Dog