Thermoquad tuning on 318

remytherat said
Right now there are two issues I am facing: stumble right off idle and major bog when secondaries open. Idle mixture screws set for highest vacuum (21" Hg). Accelerator pump in either position did not affect situation. Metering rods adjusted 2 rotations from bottomed out. Air valve wound up about two turns. When given gas in neutral, throttle response is very good and secondaries open perfectly. In drive there are the above problems. Off idle stumble can be driven around by very slowly easing onto the throttle, after which the car acts normally. When the peddle is punched to the floor, the car dies and bump starts itself when foot is taken off the gas. When the secondaries are eased into over the course of 10 seconds or so it runs very well.

Engine info
6
Original unmodified 1969 318
Stock cam
1972 340 intake
1972 small primary thermoquad
Stock advance curve, ~12˚BTDC initial timing
2 1/4" h pipe exhaust

There is more than one hole in the accelerator pump arm that attaches to the top of the carburetor. Make sure the rod going to the throttle linkage is in the hole closest to the carburetor body. That increases the pump shot. Also, FWIW, 12 degrees initial I would treat as a minimum starting point. That engine is low compression and can stand a good bit of initial timing. Maybe pull in to 16 initial and drive it. As long as the engine continues to idle up as you pull in timing it's wanting more. You may of course have to readjust the idle speed when you raise the initial timing. It's needing more initial timing because it's trying to inhale a bigger gulp of air through a better flowing intake and carburetor.