I've got a nice set of the old mechanical six-pack holley carbs. After exhaustive research on the subject, its nearly impossible or not practical to convert them to the vacuum set-up as they were never built for it. With a stock cam and no headers on a 440, is it possible to use these carbs with decent driveability. Mechanical secondary anything has never been my choice for a driver, but this set-up is a little different. Any thoughts?

you are correct , you can't change them to vac operated . you can drive with them on the street , but you might just sell them and buy a new set of vac carbs ?

Sounds like the simplest solution. The price of three new Holleys however is likely out of my league. Anybody bought them lately?

I ran a set of those carbs with a mild cam 440 and they were unbelieveably great on the street. You say you have a stock 440, stock as in 1970 specs or 1978 specs?

Sheldon

I ran those carbs. on my old motor for about 3-4 yrs. They were a pain to dial in. I ended up taking them off and putting on a set of vacuum carbs. with ProMax stuff. Love the carbs. now.

stone stock 1970 440 4Bbl. Not the HP version. a little bowl work on the 906's, fresh rings and bearings.

I ran a set of mech carbs on the street for several years with no problems. They are great. I had them on a 340 with a .508" MP cam and 4.10 gear/4spd.
They are easier to run because the fuel lines can be removed in one piece for jet changes, etc. This is a HUGE advantage at the track.
You will need to jet them up and do the standard PV swap. You will also likely need to play with squirters for the center carb.
They have received a bum rap due to all those years of MP telling us to trash them and buy the vacuum carbs. Most people who have actually taken the time to tune them and run them REALLY like them. If you don't like a double pumper on the street, then you won't like the mech carbs.

I ran them with a stock 383 HP convertor, 3.23 gears and a mild cam with Six Pack slugs and ported, stock valve 906's (very close to a stock 70 440 magnum). I left the middle carb stock, I jetted the outboards down to whatever a 700 double pumper jetting was (I think I had to drop 5 jet sizes). You could kick that thing at 20 MPH and it would respond right now and break the tires loose with no bog whatsoever.
I have a new set of vacuum carbs on my 71 Road Runner right now and although it works pretty well it still is not as crisp as that mechanical setup was.

Sheldon

I sent my set of mechanical carbs to Pro-max and had them do their stuff to them including a rebuild. The 493 inch hydraulic cammed motor they are on dynoed out at 681 hp/682 ft.lbs of torque at 5500rpm. I assume the vaccum advance models would produce the same output. The differnce is in the drivability. I like the control I get with them. They do require some thought to use effectively, but they teach you how to drive them by the seat of your pants. Too much too soon, and you feel it. Crisp is a good word to describe the way they feel. A set of well set-up vacumn carbs don't require much skill. You just mash the pedal and they do the rest. Mushy sounds about right to describe the difference.

I ran a set of the mechanicals back in the late '70's early 80's and absolutely loved them. One day the outboards stuck open on the freeway, which gave me a feeling that I'll never forget. I had to stomp on the pedal again to get them to release. What a ride!

As usual, lots of good informed opinions have come back to help out. Thanks Guys.

I am intrigued by the idea of mechanical linkage opening my outboards instead of the stock vacuum. Is there a mechanical linkage conversion setup available for the stock 1970 six packs?

Some people used to use a mechanical linkage on the stock carbs to force them open before the vacum would kick in and do it, but with no accelerator pumps on the outboards you are going to have transition problems. Getting your vacum cabs set-up properly is a drastically better solution.

A mechanical setup really needs accelerator pumps on the outboard carbs. There use to be a company called "Six Paks To Go" that did just that. You sent them your carbs and they modified them with pumps and squirters, and a mechanical linkage,etc. The parts required to do the job were almost entirely off the shelf Holley rebuild parts, with the exception of the linkage. A little drilling, a little grinding. They even relocated the idle screws for easy access.

i ran a set of the mechanicals back in the early 70's. tuning was much simpler than the stock carbs because there wasn't any emissions garbage in the carbs. i used a progressive linkage and they drove quit well. from a performance stand point i preferred the vacuum carbs. the vacuum carbs seemed to have more mid-range power. probably due to the controlled opening rate.

Hi there. Do you have a complete setup right now, or just the carbs? Here is a sight, all tho it's for Ford Carbs, that has a lot of great pictures and technical info that might help.
http://www.gerlecreek.com/documents/tptechnical.htm
One question I have is do you know much about carbs right now? The reason I ask, is by time you get them on and tweaked just right, you will know the carbs inside and out. Some people buy a used setup and then pull their hair out because of problems (previous owners) which is sometimes why they were for sale in the first place. It takes a lot of perserverance to work and get them just right. But having said that, when they're right, they are AWESOME! You might have to mail order a few parts also, looking at where your from too. Promax and Quick-Fuel make great products that will cut your tuning probems/troubleshooting time to a minumum. If your not real familiar with tuning carbs, you may want to send them off to Promax and have them set them up initially. Promax has a dyno they can test each carb you send them prior to getting them back. It just depends on how comfortable you feel tinkering with them.

Here's a book on E-bay you may want to look at also. May be availiable other places on the 'net also. E-bay # 270261211020

where can i get the progressive linkage for the mechanical carbs been looking but cant find anyone who has it cudaman72383@hotmail.com

The mechanical six pack set-ups DO have accelerator pumps on the outboard carbs!!

Regarding six packs: I cannot believe how much BS (mis)information is floating around the internet, repeated and passed on my people who have never owned/run a six pack. Same thing with 426 hemis...

I had a set brand new in the box that I sold about 6 yrs ago. I can not find pictures of it with the box and part number. Sorry.