'64 327/300 Throttle Spring

[Garry E.]

Has anyone come up w/ a good alternative to the stock throttle spring on the Carter AFB? I had my carb rebuilt, but I find now that the stock spring isn't strong enough to bring the idle back down to the 600-650RPM range (the car has a PG trans...)

I've seen some people use a combination of two springs to solve this problem, but I wonder if there is a better single-spring approach

Thanks

Garry
#38705

[Timothy B.]

Re: '64 327/300 Throttle Spring

Garry, Is there any binding when moving the throttle? I know this does not answer your question but the stock spring should work fine by itself.

[Garry E.]

Re: '64 327/300 Throttle Spring

Garry, Is there any binding when moving the throttle? I know this does not answer your question but the stock spring should work fine by itself.

Tim:

There is no binding and the action of the throttle is smooth and even. The problem is that the spring doesn't pull the throttle far enough forward to idle-down the engine..... The spring is stock - purchased from Long Island Corvette. It is the correct color and shape.....

[Bob R.]

Re: '64 327/300 Throttle Spring

I bought a repo spiring for my 63 300hp and had the same problem. It doesn't have enough tension to allow the car to idle properly. Let me know if you find a good solution. I ended up finding a spring at Pep Boys and installing it. It doesn't look correct but it does work correctly.

[Timothy B.]

Re: '64 327/300 Throttle Spring

Garry,

To answer your question I can only suggest a spring from Home Depot etc. that has more coils. The feel of the accellerator pedal will feel different so you may not be happy with that.

Do you think the throttle shaft is wore on the AFB causing the shaft not to set back in the same position, generally when this happens the throttle shaft has wore in the aluminum carburetor housing. It could also be the throttle plates not set properly in the bores of the carburetor if someone has had it apart.

Double check the throttle lever to make sure the ground strap if it's attached is not interfering with the returning lever and also the insulation inside the car to be sure it's clear. Some members have reported the reproduction accellerator pedal is very stiff making the throttle hang a bit so check that also.

If everything looks free I think you may have a problem with the shaft inside the carburtetor. I know you just love to hear this but it's really not the bad to fix.

[Garry E.]

Re: '64 327/300 Throttle Spring

I bought a repo spiring for my 63 300hp and had the same problem. It doesn't have enough tension to allow the car to idle properly. Let me know if you find a good solution. I ended up finding a spring at Pep Boys and installing it. It doesn't look correct but it does work correctly.

Bob:

I ended up using a clutch spring from a '63..... It's about the same length but much stronger..... It seems to be working pretty well....

[Stuart F.]

Re: '64 327/300 Throttle Spring

As long as I can remember, I've always had this problem with my 63 w/AFB's. Now, that includes 3 different carbs, i.e. the original 3461S that was stolen from me, the replacement (substitution) 3720SA, and my new (1985) 3721SB. I still use one of the latter 2 carbs as I had been experimenting with them over this past couple years. On the 3721SB, I use a light 1/4" dia. booster spring that parallels the stock spring and is hardly noticeable, and then on the 3720SA I use this same booster from the autotranny hole on the bottom of the throttle arm back to a small bracket on a valve cover screw. Now mine is a L-76 w/4-speed so I don't expect or need a steady idle, unlke yours with L-75 and Powerglide. I used to modify white springs (those incorrectly specified for mine), but I now employ the standard black spring. Neither made much difference, so I guess it's just the nature of the beast.

I would suggest you go with the booster for normal driving and you can always take it off for show. If you are like me, you want a good throttle feel - not too soft and not too stiff either. The light booster I use gives me just that.

Stu Fox

[Garry E.]

Re: '64 327/300 Throttle Spring

Stu:

Thanks for the response..... It's nice to know that I'm not the only one with this problem...... In the interim, I'm using a clutch return spring from a '63-'64..... It is about the same length (had to shorten it a bit....) and it provides good return of the throttle..... However, I don't see this as the long term solution......

Garry

[Stuart F.]

Re: '64 327/300 Throttle Spring

It is ironic that such a little thing as a throttle return spring can be so contrary, i.e. many spring applications on C-2 Corvettes hook into a hole in the upper part of the throttle arm while others hook into the throttle rod to perform a dual function in place of a cotter key in the rod (most common). The spring itself must have the correct length of straight (uncoiled portion) so as to not interfere with the linkage at WOT. That was the problem using the spec white spring, i. e. if you tried to use it as is, it was too long, and if you cut it down the straight portion too much it would cause the coiled section to interfere at WOT. The only one I found that fits right (black), is a little too weak - can't win. That's why I use the little booster as it is just strong enough to help hold the idle steady, can be used inside the black spring or separate, and yet is small and flexible so it won't interfere with the linkage at WOT. I have had it many years and have tried to do without it, but always come back to it.

Stu Fox

[Michael H.]

Re: '64 327/300 Throttle Spring

That was the problem using the spec white spring, i. e. if you tried to use it as is, it was too long, and if you cut it down the straight portion too much it would cause the coiled section to interfere at WOT.

The white spring was part of the problem. It was never supposed to be used for a 63 engine, even though the parts book shows it as such. It was a misprint from the beginning.
The white spring was used only on a 340 HP for 62, not 63.

At least one of the reproductions available today is the white spring.

I don't remember the correct part number off hand but it's listed in later parts books as being used for 64 to 66?

There is a previous in depth discussion on this exact subject.