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Author Topic:   4300 experts? Missing linkage
Fastback68
Gearhead

Posts: 1746
From: Sucat, Paranaque, Philippines
Registered: Jul 99

posted 08-13-2002 11:33 AM     Click Here to See the Profile for Fastback68   Click Here to Email Fastback68     Edit/Delete Message   Reply w/Quote

This Autolite 4300 is not exactly the same as mine, but the missing part is right there for me to see. It's that rod that disappears into a slot in the body. On the outside, it connects to the linkage that opens the upper planes of the secondaries.
Without this rod, am I right in thinking there's no way my secondaries can be functioning?
And can I fabricate one with the right wire? The problem is, I can't figure how it would work. When I open the body, there's a recess in the carb base that is clearly designed to take the other end of this rod, with a tiny "cross member" that looks like it should serve as a hook. But if the rod is simply a straight piece of wire, there's no way it can descend into the carb body so the secondary planes can open.
I bought a parts carb yesterday, but it's missing on that one too
Can anyone explain what this part looks like that I'm missing?
Thanks a lot,
Simon

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Clark
Gearhead

Posts: 592
From: Rowlett,Texas
Registered: Aug 99

posted 08-13-2002 01:51 PM     Click Here to See the Profile for Clark   Click Here to Email Clark     Edit/Delete Message   Reply w/Quote
Your right about needing that rod and if you need one or good advice contact the people at www.ponycarbs.com Excellent support and good people.

------------------
69 351W Sportsroof Deluxe

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68 S-code GT
Gearhead

Posts: 1129
From: Sayreville, NJ, US
Registered: Mar 2000

posted 08-15-2002 08:05 AM     Click Here to See the Profile for 68 S-code GT   Click Here to Email 68 S-code GT     Edit/Delete Message   Reply w/Quote
I think there should be a plunger or piston on the other end. I?ll take a look at one of the parts carbs I have when I get home!

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68 S-code GT
Gearhead

Posts: 1129
From: Sayreville, NJ, US
Registered: Mar 2000

posted 08-16-2002 07:40 PM     Click Here to See the Profile for 68 S-code GT   Click Here to Email 68 S-code GT     Edit/Delete Message   Reply w/Quote
It?s called a secondary air valve rod and piston. The rod goes into the carb where it is connected to a small piston and there is also a spring that will sit below the piston. The spring will push the rod up and close the secondary air valve or plates closed when your foot is off the gas.

I also found out that the screw that you had in the back of one of your carb is called an idle air bypass screw. What it does I can?t tell you! I have 68s and 69s but they have neither!

[This message has been edited by 68 S-code GT (edited 08-22-2002).]

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Fastback68
Gearhead

Posts: 1746
From: Sucat, Paranaque, Philippines
Registered: Jul 99

posted 08-16-2002 08:39 PM     Click Here to See the Profile for Fastback68   Click Here to Email Fastback68     Edit/Delete Message   Reply w/Quote
Heh thanks a lot! You've obviously put some work into this - much appreciated!
Idle air bypass screw ... hmmm.
Simon

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68 S-code GT
Gearhead

Posts: 1129
From: Sayreville, NJ, US
Registered: Mar 2000

posted 08-17-2002 03:34 PM     Click Here to See the Profile for 68 S-code GT   Click Here to Email 68 S-code GT     Edit/Delete Message   Reply w/Quote
There is also a spring that the idle air bypass screw holds in.

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Fastback68
Gearhead

Posts: 1746
From: Sucat, Paranaque, Philippines
Registered: Jul 99

posted 08-17-2002 10:23 PM     Click Here to See the Profile for Fastback68   Click Here to Email Fastback68     Edit/Delete Message   Reply w/Quote
That's right. I pulled the idle air bypass screw all the way out last night. It's really long, and maybe, just maybe, is intended to cover or uncover a tiny hole I found deep inside the venturis. The spring, however, has no apparent function.

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68 S-code GT
Gearhead

Posts: 1129
From: Sayreville, NJ, US
Registered: Mar 2000

posted 08-22-2002 11:14 PM     Click Here to See the Profile for 68 S-code GT   Click Here to Email 68 S-code GT     Edit/Delete Message   Reply w/Quote
Were you able to open the pictures I sent you?

The 68 shop manual makes no mention of the screw but does show a cavity there in a cross section of the carb. The rebuild kit instructions say to turn it in all the way and then back it out 3.5 turns. What year carb is it?

[This message has been edited by 68 S-code GT (edited 08-22-2002).]

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