[QUOTE=kingbuzzo;6479053]Thanks Chiphead...this helps me a lot...would you recommend a different spring or a cliff type rebuild for a q-jet if the carb is from an unknown origin?
Quote:
Originally Posted by chiphead
I run the 2802 in a 69 400 with 62 heads, RPM and headers. Idles at 850 with 13"-14" of vacuum, has a pretty good lope. Powerband is 1500-5400. 16* BTDC, 35* all in. It's too small for a 9.5:1 455 if you're wanting to revv it over 5100 RPM
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Not sure if you're running a vacuum secondary holley or a Qjet? Either way, they're both vacuum secondary carbs. The holley would need a stronger spring in the secondary dashpot to keep it from opening too soon. The Q-jet may need a secondary flap spring/cam/pulloff rebuild. For a Qjet, I think the baseline on the spring was 3/4" turn past where the doors shut. Pulloff release time of 1.5-3 seconds depending on converter and gearing.
The OP should likely re-baseline the tune with a stronger secondary spring. 02 sensor AFR and vacuum gauge really tell you what the carb is doing. Low vacuum and lean AFR dip going to heavy throttle would indicate too-fast secondary opening. The other thing that I wonder about is the converter. Is it flashing to a high RPM, or is it coupled pretty well to the engine? A 455 with a 2802 should pull pretty hard to 4000 RPM or so. If the converter is flashing really high, that may keep the engine from doing its best work. I've seen converters so loose, that the car has to catch up to engine RPM.