1966-1967 Big Block Accelerator Rod Return Spring Bracket

[Mike B.]

Hello Guys,

The current 1966 TIM & JG states on page 117 that the accelerator return spring bracket with manual transmission has no "step" to its bottom edge. This may also apply to 1965 & 1967?

My question is does this apply to both L36/390hp and L72/425hp factory installed engines? Some folks have told me that the L36 should have the "step." I've searched the TDB archives to no avail. Here's 4 good photos I've grabbed from the online auction site. The darker rusted bracket is said to be an original $$$ and the orange painted one is either a service replacement or repro with the zig-zag "step" on its lower edge.

I'd appreciate your knowledge here,
Mike

[Joe L.]

Hello Guys,

The current 1966 TIM & JG states on page 117 that the accelerator return spring bracket with manual transmission has no "step" to its bottom edge. This may also apply to 1965 & 1967?

My question is does this apply to both L36/390hp and L72/425hp factory installed engines? Some folks have told me that the L36 should have the "step." I've searched the TDB archives to no avail. Here's 4 good photos I've grabbed from the online auction site. The darker rusted bracket is said to be an original $$$ and the orange painted one is either a service replacement or repro with the zig-zag "step" on its lower edge.

I'd appreciate your knowledge here,
Mike

Mike-----


What is the center-to-center dimension between the 2 bolt holes of both brackets?

[Mike B.]

Hi Joe,

Sorry, I'm away on business and can't measure my intake manifold holes for you. Bubba tossed my original bracket so I don't even have the correct bracket yet. I'm in the market for one. The reason for this post is so I don't buy the wrong part. It would then end up in the pile with the others I've bought through the years.

Mike

[Joe L.]

Hi Joe,

Sorry, I'm away on business and can't measure my intake manifold holes for you. Bubba tossed my original bracket so I don't even have the correct bracket yet. I'm in the market for one. The reason for this post is so I don't buy the wrong part. It would then end up in the pile with the others I've bought through the years.

Mike

Mike-----

I'd measure the distance on the bracket not the manifold bolt holes. I realize they should be the same. However, the reason for my question is I wanted to eliminate the possibility that, while of similar configuration, the brackets are actually for different engines.

I can only find that one accelerator spring return bracket was ever used for all 1966-67 big blocks. That bracket was GM 3876720. It is, of course, possible that there was a change made to the bracket without a part number change sometime during its PRODUCTION use or period of its SERVICE availability. The 3876720 was discontinued without supercession in July, 1980.

The center-to-center spec between the 3876720 bolt holes should be 3-1/8".

[Mike B.]

Thank you Joe,

Excellent information as always!

Mike

[Robert P.]

I have one off my 66 L36 and it has no step, just like the rusted one in your pictures
Bob

[Mike B.]

Excellent Bob,

Now we're talking! Thank you.

Mike

P.S. Don't lose that bracket. There's crazy people online asking hundreds for one of those!

[Vernon S.]

Hi Mike, attached you can see the original return spring bracket on my 66 L36. As you know our cars were only days apart. Before it’s said, I know that the return spring on my car is not correct but that’s a story for another day.

[Gary B.]

As an interim solution, couldn’t you file or mill away that zig-zag step to make the repro bracket look more similar to the GM original? Yes, that would make part of the bracket thinner, but that might be less visually obvious than having the step.

Gary

[Patrick H.]

As an interim solution, couldn’t you file or mill away that zig-zag step to make the repro bracket look more similar to the GM original? Yes, that would make part of the bracket thinner, but that might be less visually obvious than having the step.

Gary

I had the same thought.
I'd un-step that repro bracket.

[Anthony Y.]

Hi Mike,
I just went and looked at my return spring bracket. 1966 L36 assembly date 4/14/1966.
There is no step in my bracket.

[Mike B.]

Thank you Skip for sharing your photos in post #8. This gives everyone an idea of how an original accelerator rod return spring bracket sits when installed. I can clearly see how your bracket tilts up and over the square intake boss there. No need for a cut "step" into the bracket. Very impressive that you've owned this '66 AC L36 coupe for 56 years now and have kept it with its original parts!

Here's a closeup of another installed bracket with the "step." I can see that it lays flatter and wraps around the square intake boss there. I'll buy a service replacement/repro with this cut and live with any criticisms till I can find an original that's reasonably priced. I won't modify it, although it's tempting. Good idea Gary and Patrick. Thanks for reporting your original Anthony!

Mike

[Jack M.]

Mike- Instead of 'shaving' a reproduction bracket flat, why not attempt welding material to the indented edge?
If therez a fear of it not holding (due to the arched pressure from below), I have a second possible solution.
Since the reproduction brackets are fairly inexpensive (< $10), consider ordering two (2) of them...
Cut out a large section (purple highlights on #1), move it over, notch & weld it in place (#2).
Herez a simple animation... smooth it out, paint it orange, and you're set:
bracket-ani.gif

[Joe L.]

Thank you Skip for sharing your photos in post #8. This gives everyone an idea of how an original accelerator rod return spring bracket sits when installed. I can clearly see how your bracket tilts up and over the square intake boss there. No need for a cut "step" into the bracket. Very impressive that you've owned this '66 AC L36 coupe for 56 years now and have kept it with its original parts!

Here's a closeup of another installed bracket with the "step." I can see that it lays flatter and wraps around the square intake boss there. I'll buy a service replacement/repro with this cut and live with any criticisms till I can find an original that's reasonably priced. I won't modify it, although it's tempting. Good idea Gary and Patrick. Thanks for reporting your original Anthony!

Mike

Mike-----

I'd forgotten about those raised bosses on both the 3866948 (cast iron) and 3885069 (aluminum) manifolds. I'd say that fitment of the bracket without the relief would be quite problematic although from some of the photos it looks like it could be done. However, such a fitment would be very "un-factory-like". I now strongly suspect that the bracket was modified with the relief sometime during the PRODUCTION utilization of this bracket and without a part number change. It would be interesting to see what the bracket looks like on original, unmolested 1967 big block applications.

[Mike B.]

Joe,

I'd like to hear from some of the '67 BB owners as to what style brackets were originally installed on their cars too. But seeing as though the title of this thread refers to 1966 I'm not confident as to any of them reporting what they have. But so far three 1966 L36 owners have chimed in stating that their brackets appear as the first photo that I attached in post #1. Here's a closeup of that shot and I can see a slight flattened bend in the bracket's forward end just above where the square boss would lay. I can see that Skip Steinmann's L36 bracket photo shows it laying above the boss in post #8 as well.

Mike