Inliners International Forums General Discussion Blown and Injected vacuum advance w/ turbo

What do you do with the vacuum advance when you turbocharge? Running an HEI with a Mallory Box and a blow through carb.

56er,
ultimately electronic timing control referenced from a map sensor is best. you cannot do that with a stock hei and the mallory box though.

i have a # of vacum/boost cans that i modify to fit onto the hei dist. these will pull 10 degrees of timing when you hit around 6-8 lbs boost and yet supply the vac advance needed for driving. tom

Mechanical adjustments tend to be linear, with electronic timing you have much more flexibility. e.g. you can pull all the advance out just when the turbo starts to spool to build boost faster then add advance back in.

The mallory box is the digital one and has a boost retard feature that uses a map sensor, although I don't know what the available rates are. My brother bought it to get rid of the MSD with the boost retard box he was using, then he went took off the blower on his car instead and went to a fogger. So I can do some electronic timing control, although it will still be basically linear, just proportional. Should I just not hook up the vacuum advance at all, or just hook it up normally, or?

Vacum advance is really needed for a street car.

here are some basic settings to aim for.

timing / fixed/ mech / vac
idle / 8-12 / 0 / 10
cruise / same / 22 / 10
power /same/ 22 / -(5-10)depending on boost

Is 22 degrees total timing kinda low for cruise?

MBHD

hank,
maybe i should have also said.

total timing= fixed+mech+vacum

so at cruise you should expect about 42-45 degrees total. tom

That sounds more like it.
Thanks !


MBHD

pappy is olde skool, he don't like all this lektronik stuff.
So he got one of Tom's vacuum cannisters & he luvs it !