Okay folks, I just got a MSD streetfire dist. I understand its got 18* mech. in it at 3000rpm. BUT what do I do about the adjustable vacuum advance? I checked the vacuum port at the carb and getting 15-17 inches. looking at the chart it loks like if I leave it at 0 turns I get something like 18* Is this about right? or am I totally off the mark? basically the dist. is going on my 77 jimmy. its got a 8.5 to one 307(yes its a 307) thats 60 over. performer cam and intake, 600 holley, small tube headers. 1.94 valve. The motor is real sluggish reving up. I figure just get a new dist to start with. So I figure start at 14* for a total of 32* as long as it cranks okay. My main question is what to do about the vacuum adv.?? thanks Jim

Check at summitracing.com. Accel (as well as others) make asj. vac advance cans for HEI that "should" work with the MSD. Note that the "HEI" advance cans are different from the "points-style" advance cans. I believe your dist. will use the HEI parts.

http://store.summitracing.com/partdetail.asp?part=CRN%2D99600%2D1&autoview=sku

From what I've read, the accel vac advance kit is preferred because it lets you control when the adv. comes in as well as how much max vac advance you'll get.

FWIW, on my 307 with a similar setup and 9.5:1 I run 18 initial with 18 more mechanical in by ~3000 and it's pretty happy.

Also, there's a metric plethora of info on advance cans in THIS THREAD (http://www.chevelles.com/forums/printthread.php?t=19938)

well we installed the msd dist. started at 14 initial, for a total of 32, starts and runs good, went to check the vacuum adv. turns out the brand new can was no good. Stuck the factory can in it. got another 12 for a total of 48. jim