Fuel injection plugs

Shannen Durphey shannen at grolen.com
Mon May 3 03:20:45 GMT 1999


Bruce Plecan wrote:
> 
> 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
The electronic Q's just aren't that common.  I've only worked on a
handful of them.  I was told by a GM Training Center guy "just throw
it out and get a Holley" when I was in college.  Wish I'd known ya
then, I needed something to come back with.

Secondary jets... I've changed the later style to the early ones.  The
early ones look more like a cup than a stamped orifice.  The height is
a little different, I was playing around.  In the beginning I had some
silly notion of using replaceable jets.  I've mostly seen the rods
wear enough to be a problem, but I've pulled a couple orifices that
were worn to an oval in a 1 ton field service truck. Lotsa fuel at
WOT, looked like a diesel.  Good thing I saved the drill bit.

On my own stuff, I try to find a carb without the idle air bushings. 
These also usually have larger holes for the mixture screws.  Try to
simplify things a bit.  Ever run into a hanger with one arm at a very
different height?  I've gotten a few, don't know what caused it.  Each
one was causing a pop from the secondary, got to be the first thing I
looked for.

30 mpg, that's great.  I thought I was doing well to get 18 from the
455 in the Monte.  Neat thing, was 18 with 2.26 rear gear, still 18
with 3.08 gear.  Runs out of cam with 3.08 though.  I heard about your
"carbfire" manifold.  I never tried that with mine, didn't know I
could remove the extra casting.  Still love the crossfire setup, way
underrated.
Shannen




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