Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

General tip in question.

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Cliff Ruggles:
The 17058253 is an excellent unit.  Very little need to modify very much with one of those to set it up.  The airbleeds can all remain stock, it may need larger idle tubes/DCR's and a little idle bypass air for engines with "hefty" cams in them.

They main system really benefits from using our custom metering rods in lieu of the larger factory "K" series rods. 

The CV secondaries aren't too far off either having .052" tips.  We may drop down to our .044" secondary DA rods for some set-ups, others will be fine with the larger CV rods.

All in all a very good carburetor and big cfm too.......Cliff

Pav8427:
Built it to recipe 2 w/ mods suggested from book. Air flap notches,.093 drilled idle screw holes ect. Did use CV rods with the tips nocked down to .048. First fire up was nice. As soon as it got gas went straight to smooth 800 RPM idle. NEVER had one do that. First initial tune and drive was NICE. Another session tuning, and would hope its all nailed down.

Pav8427:
Another question I have. From the tip in description in the book, and various posts, the mention of pulling a small vacuum hose to varify settings is clear. What is not clear is, do you pull a hose while at 2000-2200 during the tip in procedure? Or when back down at idle speed?

Cliff Ruggles:
Pulling a small manifold vacuum hose can be done for either idle or "tip-in" at 2000rpms.

If pulled for an idle test, idle speed will increase slightly and will allow you to lower the idle speed screw.  If nozzle drip was present, it may go away, telling us that the carb needs some additional idle bypass air to stay on the idle system.  This assumes that control with the mixture screws is still present during the test.

If you pull a small vacuum hose during the "tip-in" test it leans things up slightly.  Depending on whether or not the engine speeds up, slows down, etc, it can help determine if you need to raise/lower the metering rods a little more or go in and change parts to changes part throttle A/F.

One also has to consider that a "tip-in" test around 2000rpm's is a no-load test and just helps get you close.  A road test should follow and further adjustments made based on what the engine actually wants or needs.

We always tune for best results in all areas.  What many folks don't realize is that the carburetor is a load sensing device and will add fuel when engine load/throttle angle, pressure differential above/below the venturi and airflow past the boosters dictates.  This happens even when we don't change parts or adjustments to the APT system. 

Carburetors by design have been doing this quite well for decades, and why we still see them in service today despite the fact that fuel injection has been around and commonplace for 30 years or so at this point.......Cliff

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