2X4 Throttle Linkage

rcull

rcull

Team Member
Whenever I see a dual quad throttle linkage it has a spring between the bolt head and the trunnion. The parts book does not show one.

When I look at the linkage, I think if there were a spring here, it would have to be of a specific design and would show in the parts books, which it does not. I have the turnbuckle. On the rounded end, trunnion end, it has a smooth bore hole about 1.125" deep before it has threads. I am suspecting that there may have been some kind of locking device that secures the bolt from turning in the bore.

Probably all wrong, but maybe someone knows!

I have attached the image from the parts book.
2x4-throttle-linkage.png
​

Thanks!
 
1373763 Spring, operating rod adjuster front bolt

Bob, turns out there was a second version of the dual quad carb linkage introduced in mid-65. The second type uses this spring 1373763 along with a few different parts vs. the first type linkage shown in the picture. The second type linkage carried on into 66.

Could not not come up with a picture of the later linkage. It came out too late for the 65 shop manual. Then the dual quad became a dealer-install-only option in 66. The dual quad does not appear in the 66 shop manual. There is probably a 65 service bulletin showing the second type.

Carbs using the the second type linkage have -SA or -SB model number suffixes.

The details were dug up in the Group 3.430 parts listings of the 72 Buick master parts catalog available on line at www.wildaboutcarsonline.com
 
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I don't seem to have access to the site you mention without purchasing a membership:(

The picture I show above comes from the the '68 parts manual, and I can not find mention of the spring in Group 4.430 in that manual. It would be nice to have a copy of the 65-1/2 service bulletin and recommended adjustment procedure. I do have the procedure from the '64 and '65 manuals and that is why I was questioning the spring.

For earlier systems without the spring, there must have been some way of securing the secondary bolt from simply walking out. I wonder if the relieved area about 1.25" deep into the Turnbuckle had some sort of resisting material in it.

Thanks
 
Attached are the 1972 parts list pages showing the two linkage types.

Would presume the front bolt going into the turnbuckle does not provide any adjustment and bottoms out in a blind threaded hole. The only way I see to lock the bolt in place is to use Loctite thread locker. Maybe the relieved bore in the turnbuckle is there to keep Loctite off the sidewall and only on the threaded area?
 

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The thread hole in my turnbuckle goes completely through, there is no bottom. Only the rod to the rear carb has an obvious locking nut. It looks like an OE piece.

As most of the carb setups have the spring and it was only offered in late '65 and '66, does that mean that many were retro-fitted, or were the 2X4 not that popular until '66?

Did we have Loctite of any kind in the early-mid 60's? I remember more locking wire and washers.
 
It is hard to tell what is going on here with the second design. Someone on another website thought that the second linkage type was introduced to prevent binding. Whatever the reason, the redesign did not elevate to a recall campaign or else parts would not have still been available for the first type years later.

My guess is the 2X4 setup was losing interest from buyers after a couple of years. First it was downgraded to a dealer-install-only option, then discontinued when a new dual quad manifold design would have been needed for '67 models. Seems like Buick was one of the last, if not the last carmaker to introduce a dual quad setup.

Don't remember seeing Loctite in those days either. Their website indicates it was around back then however. The old timers I knew from that era swore by Form A Gasket No. 1 for any type of semi-permanant sealing/locking applications. That stuff would have hardened up enough to hold the front bolt firmly in place.
 
Well, I have pretty much decided on how I am going to try it for now.

I am not going to use the spring. The problems with the spring as I see it are, If you bring the bolt in to contact you pretty much loose the progressive aspect of the linkage and open all four primaries as the same time.

I will lock the bolt in place with blue Loctite. The bolt is listed in the adjustment instructions as a "self locking bolt". I cannot see how that was accomplished on the bolt I have. My bolt is chrome, and may or may not be original, I tend towards original except for the self locking aspect.

The draw back of trying to use the spring is, by eliminating the progressive primaries, the car will feel exceptionally responsive, but will be much harder to get acceptable mileage from, especially around town. A spring would of course reduce or eliminate binding in an improperly adjusted linkage. I think with this setup it would be a good idea to check adjustment any time you removed a carburetor.

Thanks
 
A bolt (hex head cap screw) with nylon embedded in the thread area came to mind for a self-locking bolt. I just picked a thread size and length as typical.

https://www.mcmaster.com/#91211a127/=17u58mt


Just came across the attached service bulletin 65-127. It explains some things about the second type of linkage.
 

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That spring we're talking about is so thin & flexible it really wouldn't hinder operation. As I stated I believe it was an anti-rattle spring.
 
The spring that came with mine only barely collapses as the pressure is applied, and would only serve to avoid binding. If it is not the correct one, it would be nice to know what the gauge, number of windings and length of a correct one was so that it could be matched.
 
Tom, thank you for your response. I believe you to be correct.
After reviewing many images of springs used on the 2x4s, it appears maybe more than 1/2 of them have a spring similar to the one which was on mine, which I now believe to be wrong. It is too heavy to allow the linkage to be progressive. There are some images showing a very light spring which I believe to be the one described by you, which would be able to act as an "anti-rattle" spring, and have minimal impact on the progressive action of the progressive linkage.

I have seen a repro linkage on ebay which appears to have the same spring as mine, and another image of a repro on Russ Martin's Nailhead.com site which has a spring appearing at least close to what the original should be. The original appears to have only 3-4 windings in its length and be a very light gage.
 
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