Original throttle linkage to triple Weber 42's too stiff, awkward

[bloxman]

I am experiencing some throttle linkage issues with my triple Weber 42 DCOE's

I am thinking that because my car was originally a EFI (1975) that perhaps the positioning of the arm and swiveling bracket that mounts on the firewall may be slightly different than say an earlier Z that originally came with carbs.

I have tried a variety of configurations to get the arm to line up square and tidy to the Carbs , the only thing that works even remotely well , is to leave out one bolt to the firewall and move the whole mechanism to the second whole. works o.k. looks like sh#t.

This is the only situation I can think of where being too stiff is not good. Sorry if that was in bad taste just sorta slipped out

Any thoughts? recomendations?

Regards

Bloxman

[geezer]

When I mocked mine up I used this to go by and it worked fine, but it was a carb car to start with.

[mark belrose]

A couple of thoughts: First, does that single spring seem overly strong? Hard to tell from the image exactly how much tension it is creating. On my street car I played around with spring tension on my triple 40's for a long time before I found the right combination. In any event, I'd recommend using at least two return springs instead of one stronger one, since if you are running only one and that breaks, you are SOL and risk blowing up your motor.

Secondly, the geometry of the linkage at the firewall looks pretty poor. I believe you'd have a lot more leverage if the large rod connecting all 3 carbs was linked to the smaller rod at close to a 90 degree angle rather than the 160 degree or so angle it's at now. Try disconnecting the small rod and with your hand pull on it to see how much effort it is takes to rotate is using the current geometry. You should notice that as it rotates to where the arm is near vertical, it should be a lot easier to pull (again assuming your return spring is not overly strong). To remedy the geometry, it may require loosening and rotating each of the three arms that are clamped to the main linkage rod.

Best of luck,

Mark Belrose

'70 restored C Production 240Z privateer

[bloxman]

Geezer

Nice pic.

That is going to help a lot.

When you say "when I mocked mine up" are you saying you have Webers also?

As far as the diagram you sent, yes that system (70-78 accelerator controls) is exactly what is there.

but...

I am thinking that maybe I will need a shorter version of # 10 (rod), it lists three different part #'s for 240'Z, 260/80'Z, ZX'z

Mine just seems ridiculously too long

Also the greyed out piece beside #'s 12, 11 does not show the "tab" on it that the #10 rod attaches to.

The tab seems at the wrong angle .

Anyway , I think the previous owner was going to do a V8 swap on this car and may have altered things slightly.

I'll put things back the way I found the and shoot some picks for dicussionary purposes.

Thanks again

[bloxman]

Mark

Ah actually the spring was stronger last week than today. I replaced the spring that I found on the setup as it appeared broken and a piece straighten and clamped below on of the plug wire loom bolts.

I replaced the spring with a very similar spring from NAPA that felt a little softer and had two handy rings on the ends.

I find you comment about two springs logical I guess I should contact redline and see if the will sell me an additional spring to shaft lever.

Ya the Geometry at the firewall is crap!.

Thats why I'm looking for "Thought, Recomendations".

I had tried a softer spring , but I found it was too soft .

When driving the car I felt it didn't have the strength to fully seat the "throttle plates" because when I took my foot off the gas the car wouldn't come down to idle without sticking my foot behing the gas pedal.

Though, perhaps with two softer springs when I get the additional lever perhaps two lighter springs might work real well?

I'll shott some pics

[TBK1]

here is another reference, my converted 77, not great pics but hope it helps

[jmortensen]

How about converting to a cable? Easy to do, and eliminates all the linkage from the pedal to the carbs.

[mark belrose]

How about converting to a cable? Easy to do, and eliminates all the linkage from the pedal to the carbs.

I agree with Jon that a cable option is the best solution in the long run. If you need a shorter rod, you can do what I did: remove one of the plastic cups, cut the rod to the appropriate length, and rethread it.

Mark

[geezer]

I totally agree with Mark & Jon. There is no need to use the stock factory linkage on a GTO replica. A cable will be much better. I use cables on all my mopar projects. It's easy and trouble free. The only reason I'm using the factory linkage on my Z, which has triple Weber DCOE 45's is for the nostalgia factor. I'm only using parts that were available during the same time period, when the car was new. When I say "mock up",that means I test fitted everthing going on the car before starting the restoration which is now underway and moving quickly. Maybe you want to stay lowtech also?

[bloxman]

PICT0150.JPG

Position of linkage with mount using one bolt to hold it geometry seems straighter but..seems to bind more (too stiff)

PICT0151.JPG

Good shot showing linkage shifted over by one bolt hole

PICT0154.JPG

showing linkage put back in original position

PICT0155.JPG

Relative angle of linkage in original position

PICT0156.JPG

Rod with two red ends (which I feel is to long), also I feel the "Tab" that left end of rod attaches to is in a awkward position .

I am feeling that if the rod was shortened (providing shortening will still allow complete throttle opening), and /or the tab's position was changed then the linkage will function more smoothly.

come back

Bloxman

[240ZGL]

I've been working on my linkage too. The arms for the butterflies look a bit short. You have a near vertical stroke from arm to arm, that could be binding. You want some angle pushing down and out.

[geezer]

First, make sure your standoffs are adjusted properly at the same height with no binding whatsoever. It's important to work from one direction when adjusting carburator linkage. Once you have the rotatator rod operating all three carbs smoothly in unison, then you move on to your stock piece. Ideally it should be mounted straight back to the firewall with no angle at all. No angle up & down, or side to side. After mounting the bracket to achieve this you can then make up the adjustment on the rod with your red ball cup connectors. It might be nessesary to shorten or lengthen this rod, depending where you end up in relation to the bellcrank. One more thing. Make sure your motor mounts and trany mounts are good and where they belong first.

PS - Had to come back to say that is real purdy 240ZGL!!