Quote:
Originally Posted by Ole Don
At idle 30° or more BTDC tends to cause alarm, but there is no load on the engine. And as soon as there is, the vacuum goes away. Most engine tuners recommend a stock engine be connected to "ported" while a modified street engine will prefer being connected to a straight manifold source, mainly for the reasons mentioned.
This is why it worked so well for me, my 312 had higher compression, big valves, an Isky cam and other goodies. At idle, it had a bunch of advance, and while opening the throttle, both vacuum and advance would drop significantly. It needed 89 octane all the time, and 91 or 93 if I raced. It would eat orange 350's for breakfast. It was a fun car.
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Let me add one very important clue as to why my motors ran so well. I mailed two 57 type distributors to Bubba's Hot Rod Shop in Indy for a custom curve. Both of my good engines had one. One motor had cast flat top pistons, and rods with polished beams. This one was shifted at 5800 to 6000. The other motor had forged pop up pistons, on aftermarket rods, an Isky 505T cam, that one was shifted at 7,000 to 7200 RPMs. Both had a Pertronix. I was told after the fact that when I ran the one mile at Bonneville, everything stopped so they could listen to me. I was busy trying to keep the rear behind the front. It got loose about 120.