2x4 Carb linkage help needed

Steve Dickey · #1 (**permalink**) 03-16-2002, 07:05 PM

All,
I have never run dual quads on a car before and am questioning the linkage set-up. Specifically, the linkage to the rear carb which has a slot in it, and therefore, I presume, works in a progressive fashion. Upon careful examination of my intake manifold, there exists a runner from the front carb to the rear but it only supplies the #4 and 7 cylinders. My question is, during part throttle applications where I am running primarily of my front carb wouldn't cylinders 3 and 8 run lean??? Can somebody educate me on this?? Also,does anybody know a source for the cad plated hardware to connect the linkage arms to the carbs?
Many thanks, Steve D***ey

Toivo · #2 (**permalink**) 03-16-2002, 07:20 PM

Which manifold are you using? Part number?
On some manifolds, the plenums themselves are connected.

Steve Dickey · #3 (**permalink**) 03-16-2002, 08:11 PM

Toivo,
The plenums are connected with a runner, however two of the cylinders are left out of the loop. The manifold is some after market dual plane that says "shelby" on it. Other than that I have no other info on it-sorry.
Also, if anyone is able to post any pictures of their linkage that would help a lot. I've just gone through my collection and found no close ups of linkage details.
Thanks again, Steve

Toivo · #4 (**permalink**) 03-16-2002, 10:44 PM

Who told you you could run on just one carb with this manifold.

Usually, 'running on the front (or back) carb' is referring to 3x2's where all the carbs are lined up on a common plenum area. On old 6x2's, on the street, the middle carb on each side was often just a dummy and the engine would run using only the corner carbs. This is possible because all the carbs are setting on the open plenum area that is feeding all the cylinders.

On my setup, I use progressive linkage, but the progression is between primary and secondary. The primaries open first and then the secondaries open later; but both sets of primaries open first, then both sets of secondaries (you need to know that my 'carbs' are actually 4 barrel throttle bodies, of which I have two, and the primaries are equal in size to the secondaries, they're basically just air-control valves). The linkage is the same though, whether we're talking throttle bodies or carbs.

I don't know if this'll work or not, but here's some views of what you're probably going for:

Pictures here

Steve Dickey · #5 (**permalink**) 03-17-2002, 09:14 AM

Toivo,
Thanks so much for the reply and pictures. That set-up looks very similar to mine. It is a little difficult to see the linkage but I think I see the same slot on your linkage, on the arm to the rear "carb". It appears when the bellcrank rotates it would begin to advance the front carb first, then after 10 or so degrees of rotation the play in the slot would be taken up, and the rear would begin to advance. Because the moment arm on the bellcrank is of different lengths for each carb linkage arm, full throttle could be adjusted to be reached simultaneously. It is this apparent progression between carbs that has me confused.

Thanks again for your time and pictures, Steve

Steve R · #6 (**permalink**) 03-17-2002, 06:36 PM

Steve,
Coud you post a picture of the intake? Even if you have it figgured out, I am still interested in seeing it.
Thanks,
Steven

Steve Dickey · #7 (**permalink**) 03-17-2002, 10:39 PM

Steven,
I am currently without a digital camera. If you want to e-mail me your address, I will take a photo and send it to you.
Steve

LETSRCE · #8 (**permalink**) 03-17-2002, 10:58 PM

I'm just about done with my SPF and I'm running 2-750's. I got the linkage from BDS, Blower Drive Service. They make a linkage for inline carbs and acctualy has more stuff than you need, makes for a real clean install.

-Joe C.

Steve R · #9 (**permalink**) 03-18-2002, 09:25 AM

Steve,
I am in the same boat as you with the camera. I can't take it anymore! this will probably be the week I get one. Check your e-mail.
Thanks!
Steven

Steve Dickey · #10 (**permalink**) 03-18-2002, 10:19 PM

Steven
Right back at you. My wife unloaded the camera following a summer job as a camp Photographer thinking she would upgrade, but has been unable to decide which one to purchace. So, I have a gap in my digital pictures of my cobra build. I have no close ups of the manifold to post. I'll send you a hard copy.
Take care, Steve

65cobra427 · #11 (**permalink**) 03-21-2002, 01:14 PM

Steve D****y,

You can use my digital camera!!! Am probably going past your place Friday nite with the Cobra... When are you ready for paint... Let me know...

O'spotter

Steve Dickey · #12 (**permalink**) 03-21-2002, 08:13 PM

Spotter,
The car has been ready to go out for quite some time. My buddy is moving into his new shop this weekend, so with any luck next week or the following weekend. Where are you headed Friday eve.?? Any chance you could swing by for a few so I can see what my engine is supposed to look like when I'm through with it?? Thanks.
Take care, Steve