Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

'78 Pontiac L78 carb - stumble at idle and mid-range

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KeithinMI:
Ok, so followed your procedure and got the tubes out. I must have tapped one in slightly too far because it was a pita to extract and it was bent. :(

i did use a very fine wire followed by brake cleaner to make sure those passages were clear (and verified the other air tubes and passages were clean too.

So, I placed an order online today Cliff. Ordered the .135 needle and seat, the HP accel pump, the secondary cam and spring, and air tubes. The carb is a 17058278 which is the carb on the L78 Pontiac 400 'standard' trans am engine with a whopping 180 hp.

You'll give me the correct parts to get the most performance I can out of that QJ, right?

The only mods I have done to the car are install a low-restriction Magnaflow cat converter and a Dynaflow crossflow muffler. Still using the single intermediate pipe from the cat to the muffler which has dual outlets. Also put in a MSD digital heat hei module (to get a rev limiter on that engine) as well as an MSD HEI coil. Rest of engine is stock.

Car is automatic with TH350. Not modified. Stock torque converter as well

thanks!

Cliff Ruggles:
I don't pre-drill the idle tubes unless the order is placed by phone and we're asked to do so.  Everything else will be correct for what you are doing.....Cliff

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