Quote:
Originally Posted by M3 Mitch
I still have a 71 Impala, originally it had "transmission controlled spark" where it got no vacuum advance except in 3rd (high) gear. I went through it and de-smogged it, put on an adjustable vacuum advance unit, and can get up to about 17 MPG as opposed to Trapper's friend getting only 8 back in the day. This is with small-block 400 ci and Turbo 350 trans, 2.73 gears.
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My '71 Bonneville had that and it was a nightmare. It developed an intermittentcy where that vacuum valve would open and close rapidly at highway speed and felt like the engine had a bad irregular miss.
I finally got fed up with it and bypassed that valve altogether with a hose routed directly to the distributor and adjusted the distributor timing accordingly.