C3 427 spring

[Bruce Mitchell]

Where are the two mounting points for the accelerator spring for the tripple deuce set up? and what color was the spring?

I don't see a mounting place near the firewall, so I temporarily have it on the upper portion of the linkage and the other end is towards the Front of the manifold (I know that's wrong). Am I missing a bracket?

[Joe L.]

Re: C3 427 spring

Bruce-----

1968 was a "year of indecision" with respect to Corvette 3X2 accelerator return springs. Very early cars may have used only the same black-painted spring, GM #3921680, used for most other engine applications and located between the front carburetor fuel line and the upper hole on the center carburetor accelerator lever. They may also have used a non-color-coded spring that was "pressed into service" to address a need for a "workable" set-up.

Later 1968 with 3X2 used a YELLOW spring of GM #3937913. This spring of 3-5/32" free length was mounted between the front carburetor fuel line and the upper hole of the accelerator lever. It has been reported that, in some cases, this spring was mounted between the accelerator lower hole and the accelerator cable bracket mounted on the rear carburetor and another spring was used between the front carburetor fuel line and the top hole of the accelerator lever. I kind of doubt this since the overall spring pressure of the 2 springs would have created an extemely "stiff" accelerator. Even if only the yellow spring was used, by itself, between the accelerator lever and the rear carb mounted bracket, the accelerator would have been "stiff" due to the free length of this spring. I suppose it's possible, but I consider it unlikely.

I believe that it's possible that some very late 1968s used what is regarded as the "1969 set-up". In this design, one spring is mounted between the bottom hole in the center carb accelerator lever and hole on the side of the rear carb mounted accelerator cable bracket. I don't think that the bracket used on "earlier" 1968s even had this hole, but I could be wrong on this point. The spring used , possibly, for late 1968s and definitely for all 1969s was GM #3939748. This was a spring color-coded ORANGE, of 4-3/8" free length, and of 14 coils.

Quite frankly, if you are more interested in FUNCTIONALITY than ORIGINALITY, I would recommend using the "69 set-up".

I'd be interested in learning the approximate build date is of your car AND whether your accelerator cable bracket has the hole on the side for a spring attachment point.

[David S.]

Tripower Spring

I thought on 69 tripowers the accelerator return spring mounted to a small bracket attached to the rear carb hold down stud. That is the way mine is mounted. I do not know if this is correct but I have seen many mounted this way. Paragon also shows it this in their catalog. Does anyone know what the correct position/location is?

Dave
36838

[Joe L.]

Re: Tripower Spring

Dave------

I don't recall the spring bracket and I just checked the 1969 AIM and I don't see one shown. However, since Paragon sells such a bracket I suppose that there must have been one. There are 2 brackets that existed that I can't account for. For 1968, there was a bracket GM #3939750 and for 1969 there was a bracket GM #3960647. These could be the pieces of which you speak and those which are sold by Paragon.

As I say, I don't recall seeing them on "tripower" installations but, as I've mentioned for quite awhile, I've never really studied or been interested in 67-69 tripower set-ups. The information that I provided previously was mostly from my recollection and based on casual observations.

[David S.]

Tripower Spring

Thanks for the reply. I would only add that if the return spring (Orange) is place in the hole located on the accelerator cable braket the spring can interfere with the middle carburetor linkage. This interference in my experience has been from a slight rubbing to a binding interfering with proper opening of the front and rear carbs. Has anyone else has this problem?

[Joe L.]

Re: Tripower Spring

Dave-----

Now that you mention it, I believe that I have heard of that "somewhere along the way". In fact, that may be why the spring bracket was added. As I mentioned previously, 1968 was a year of "indecision" relative to the "tripower" accelerator spring set-up. I thought that by 1969 the whole thing had been "sorted out". It looks like it wasn't, though.