Hello, I just purchased an MSD 6AL ignition, a MSD Pro Billet dist. #85551 and a Blaster II coil.

I bought these NIB from a buddy. I really wanted the 6AL and the coil. The distributor was just a bonus.

The thing is I don't know if I should use this distributor since it has no vacuum advance. This is my engine combo:
sbc 400 balanced rotating assembly.
5.7 rods w/Milodon bolts
Keith Black Silvolite hyper pistons @ 9 to 1
Comp Cams XE284H cam 1.5 roller tip lifters
Heads are Vortec 906 castings. Machined for bigger .600 lift springs. "Airgap" dual plane intake topped of by a Holley 750 carb.
Trans is a TH2004R, 3.42 gear, car is about 3700 lbs.

I'm sure a vac. advance is more suitable for the street but should I
A.Use the non-vac adv. dist.
B.Sell the 85551 and get a MSD dist w/vac. adv.

C.Use my old HEI?

If I use the 85551 what is the best way to set it up?

All depends on your intended application...
I use the exact same MSD distributor, coil and box on the '70.
However, I've got the timing locked at 37* so no need for vacuum advance.

With Vortec heads, you're only gonna need around 33-34* total. Try setting the MSD up for around 14 initial and 20 mechanical..all in by 2800-3000 rpms.
Sell the HEI...

If you are going to do much street driving, do yourself a favor and try to get an MSD w/ vacuum advance.

When I installed my MSD Digital 6 box a few years ago, I disconnected and plugged my vacuum advance for the heck of it. I only got 90 miles on a tank of gas. :eek: I think that would make it about 9 mpg. With the vacuum advance, mileage went back to where it had been. I get right at 14 mpg. Significant difference.

What Justin said!

Application is the key. I don't drive mine much on the street and have an MSD Digital-6, Blaster II coil and a Pro-Billet with no vacuum.
Mileage sux, but I rarely drive it around town.
Maybe you can swap with someone, or sell it.

Thanks for the advice guys. Doug I was looking at your chevelle pics, where is that track that you were racing at? Have you ever run over at Havana IL? (Midstate)

Ditto on the milage, for Old Red, its a documented 20-25% difference in MPG between vacuum on and none. Hard to believe 10 degrees does that much.

You'll want it , if nothing else than to help with your idle, which won't be that smooth given the cam size and mild compression. It does not affect other performance or ET though.

Mark
1/8th mile numbers were at Chevellabration last summer in Nashville area.
Last weekend I was at Mid America Raceway in Wentzville, first time with it to a quarter mile track (second time to any track with it). I took 8th in the Street trophy class and brought home a trophy :D Now I got a cool MAR sticker for the quarter window.
I changed jets this week and added a secondary metering block and plan on going this Sunday for the last race of the season.
Best time was 13.11 at 104mph.
I may try out Havana next year.
Several winter mods planned.