Engine Tuninng

On the vaccum adavnce you need to limit the amount of advance by limiting the slot and its an age old debate but I run it to a port with full vaccum(intake manifold is best or carb base) so its advanced at idle and steady rpm (high vaccum).This helps smooth out the cam and give you better throttle response and will help gas mileage slightly.Ive run vaccum advance on my cars and havent-just depends on how much I feel like tuning it.I set up the initial with no regard to the vaccum and run around 16 crank degrees with 18-20 degrees in the distributor-then I limit the vaccum advance to 5-7 degrees.It sounds like alot of timing with it all combined but it works well in conjunction with pump gas street engines,I learned this recipe from several prfessional tuners.As far as the holley two sizes at a time is correct and you shouldnt have to jet more than four sizes up or down-if you do then thats an indication of either too small or too large a carberator.