I've had enough of my edelbrock so I picked up a used holley 4160 600cfm.
my question is it has one of these Throttle shaft conversion kits installed on it
http://www.summitracing.com/parts/HLY-20-3/ all I wanna know why would you swap out the original linkage for this one and are the any performance gains?

 

That's to control how fast the plates open and close. You will not see any extra power from it.

 

I know that, but dosen't the stock linkage do the exact same thing. I just don't get why someone would swap the stock one for this one

 

What is that kit doing on a little vacuum secondary 600? That's a linkage conversion designed for a big double pumper so that the secondary throttles open the same time and same amount as the primaries. Think: side-mount dual-quad tunnel ram application, big roots blower application, etc.

Totally inappropriate to use it on anything vacuum secondary or anything you need to drive on the street.

 

its the only linkage I got with the carb, will it still work?

 

No, it won't. First off, it's made for carbs with 1-11/16" throttle plates. The ones on your little 1850 (600 CFM vac secondary) are only 1-9/16". Second, and more importantly, it's built for a double pumper carb. Yours is a vacuum secondary carb.

A vacuum secondary carb has no mechanical linkage between the primary and secondary throttle arms (except a safety linkage to force it CLOSED, but none to force it OPEN).

You need the stock linkage on that carb. There is no "upgrade" linkage you can use on it.

If you want to change the secondary opening rate you need to do it by changing springs in the vacuum secondary vacuum chamber on the pass. side of the carb. Holley makes a selection of secondary vacuum canister springs as well as a "quick change lid" that you can install to make trying different springs a 2 minute operation.

 

I don't have a 1850, its a 4160 but whats weird about this carb is it dosent have any vacuum ports except the one for the distributor.

 

Do you have the List number (stamped on the choke airhorn) or at least a picture of it? Regardless of what the design of that 600 the kit isn't designed for it and you NEVER want to run full 1:1 linkage in a street application. Even a double pumper should still be run with progressive secondary linkage on the street (so the secondaries open after the primaries are about half way open).

 

actually I was just trying to look those up, the numbers that I found are

C3AF-9510-BK
LIST-2805
601

 

Had to resort to a Google search to find that one. Yep, it's one of the carbs on an old Ford dual quad setup from the 1960s. Here's one of the links I found to it- look about halfway down on the page:

http://mustangtek.com/4160/holley4160.html

I think they got the 2804 and 2805 carbs backwards in the listing (front carb with choke plate vs. rear carb without) but if you click on the detailed pictures you'll see which one is which. The List nubmers are clearly stamped on the airhorns in the detail pictures.

Bad news is that this is probably not the carb for you. The calibration is probably all wrong to run as a single. And if it had the original linkage it wouldn't work on your GM car.

Good news is that carb might be worth some money to a Ford restoration guy. Maybe enough to buy a whole new carb that will work!

 

ok, I have a few questions:
what does a GM linkage for a holley look like?

what would be different in the calibration? ie: jets, power valve, accel pump

I have both those carbs the 2804 and 2805, the 2804 is in a little rougher condition that the 2805

 

A standard Holley 1850 600 CFM vacuum secondary carb (universal performance replacement) looks like this:



It comes out of the box with the "GM style" throttle arm you see above. Throttle cable stud would be installed in the small hole just to the right and at the bottom edge of the big hole at the top. Auto trans kickdown cable stud would go in the hole all the way at the bottom. If you're running a typical GM automatic overdrive trans that uses a TV (throttle valve) cable they sell a bolt-on piece that bolts onto the throttle arm and puts the TV cable stud in the proper location to work with common overdrive automatics like the 700R-4 (like used in 3rd gen F-bodies) and 200-4R.

 

If you have a complete set of dual quad 1804/1805 carbs that's just GOTTA be worth some money to a person doing a restoration on an old Ford.

You can buy a garden-variety 1805 universal performance replacement carb used (in need of rebuild) off ebay for like $50. Surely a complete set of factory Ford dual quads, even in rough shape, is worth a lot more than that.

Just from a money perspective it seems to make more sense to sell what you got and buy something else. Rarely in this hobby does the money side of anything make sense, so when it does AND it makes better sense to trade it in on what will work better, you should usually do it.