Fuel injection plugs

[Howard Wilkinson]

Bruce:
    The "spreadbore" (I believe that's the term) design of the
Quadrajet results in the secondarys contributing to normal driving far
more than on carbs with equal primarys & secondaries.  As a result a
little bit of wear in these rods or orfices makes a big difference in
performance.  I could show you quite a number of Quadrajet carbs with
visibly egged out secondary orfices.... These are 100k+ carbs, and I
just throw them away and find a good one.  Unfortunately I've found
that the factory "rebuilts" often have this same problem.  Perhaps as
I deal more in pickups and trucks than in cars, the is some difference
in the operating environment which accounts for the problem...... Who
knows.   I just know that if I have one that doesn't work, it nearly
always turns out to have egged secondary jets.        H.W.

-----Original Message-----
From: Bruce Plecan <nacelp at bright.net>
To: diy_efi at efi332.eng.ohio-state.edu
<diy_efi at efi332.eng.ohio-state.edu>
Date: Sunday, May 02, 1999 7:28 PM
Subject: Re: Fuel injection plugs


>
>Your saying you've had the secondary metering rod orfices go bad?.
>By how much?....
>Never saw any worn enough that that worried me.
>Finding the optimum opending for the secondary air valve was the PITA
for
>me.
>Well right after digging up all the metering rod hangers, and many
needles.
>Then I built a jig for blueprinting the hangers..
>Once ya got the idle jet, idle channel restrictor right then ya could
play
>with the primary idle bypasses. Then you just had to diddle with the
primary
>jets, and dancing needles (ecm content).
>   Had one on a LG4 auto that ran 15.0s, and got 30+mph on the
freeway.
>Same metering also ran 13's on a 355 (crossfire manifold sorta)
>Grumpy
>
>
>> > Quadrajet would have had the most potential of any of them if
they had
>> > only made replaceable secondary orfices.... once these are worn
>> > there's nothing to be done.
>> Around 1985 a company called "The Carburetor Shop" offered a kit
>> designed to replace the secondary metering jets.  Generally I see
worn
>> rods, not jets.  Most common seems to be a "ring" worn around the
rod
>> caused by the rods "rattling" in the stainless plates that make up
the
>> jets.
>> > I've built a puller and removed them, and
>> Puller?  I have a drill bit that I've ground to cut the aluminum
carb
>> away from the jet, then a small pick easily pulls the exposed jet.
>> > I suppose you could manufacture a replacement,
>> I pull the replacement jet from an unused Q jet.  I buy the carbs
>> cheap and strip them for parts.
>> Shannen
>
>
>