Rich Secondary?

[jdon88]

I just rebuilt a 17057262 for my '76 Grand Prix.  Runs great on primary but seems too rich on secondary.  When cruising at 20-30 mph and stomping accelerator the throttle response seems flat, slowly accelerating.  This is with trans kickdown disabled.  Using CV rods and L hanger.  Tried some other rods and hangers I have.  Seemed a little better with AK rods and L hanger.  Seemed little better with AK rods and P hanger.  I have a T hanger that I can try, am I on the right track?

[Cliff Ruggles]

Not enough information.

What has been done to the engine is the GP?

Did you try the carb out with the stock hanger and DB secondary rods first?

Why is the kick-down not hooked up? 

If the transmission doesn't shift to a lower gear the engine may accelerate slowly and take a long time to get thru transition onto the secondaries.

When you say "rebuilt", what did you do to the carburetor and what was replaced?.....Cliff

[jdon88]

The 350 was originally a 2 bbl, almost 20 years ago I put in a Qjet(17054913), cast iron intake manifold, timing set, and 067 cam.  EGR, heat riser valve, and thermal vacuum switch are not hooked up.  Distributor vacuum advance connected to ported source.  18" vacuum at idle. 14 degrees timing.

I did not try DB rods but I have a set I can try.

Trans kickdown was not working and I thought I read somewhere about tuning secondary with kickdown disabled.  I cleaned and adjusted the kickdown switch and it works now.

I sent the carb baseplate to you for rebuild and bought a SR rebuild kit.  I converted to electric choke, vacuum passage blocked off.  Drilled base for .080 idle bypass, 73 jets, 44 rods, idle tubes .038, idle down channel .050, Lower idle air bleed .067, upper IAB in main body .067.

Main air bleed in main body was .055, I drilled out to .067.  Main air bleed in air horn is .070.  Secondary air flap cam and spring replaced and adjusted to 1/2 turn past closing.  Air flap opening is 1.350".  Secondary air bleed tube was.032, I drilled out to .036.  Float replaced and set at .25".  APT adjusted to 2.5 turns out.    Choke pulloff replaced.  That's about it.

[Cliff Ruggles]

Did you put one of our timed choke pull-offs on it?

[jdon88]

Yes, I installed one of your choke pull-offs.

[Cliff Ruggles]

If you aren't getting any hesitation/stumble/bog going onto the secondaries then the pull-off and spring tension for the flaps are fine.

Seat of the pants testing can be difficult and for sure the little 350 would NOT work well without the kick-down hooked up or manually shifting it.

I would also imagine a 350 2bbl would be pretty low compression so not making a ton of power right to start with.  If you really want to nail down the best secondary metering rods I'd look for a chassis dyno or wonder over to a local track on test and tune night and make a few runs.

That's what I do with my car, or did back when I was dialing it in. 

I started "pig" rich with .030" rods and increased the size .005" each run till it started "surging" just a tad in high gear on the top end of the track.  Amazingly there really wasn't a big difference from rich to going pretty lean far as ET and MPH were concerned.  The spread for all runs was barely a tenth and 2mph and most runs were much closer than that........Cliff