I installed a Summit distributor, the spec card says 11* mech & 12* vacuum. That means at 36* total w/o vacuum, I've got 25* initial timing. That's seems a bit high and the mini starter knows it. I'll take this distributor to a shop but what's a ball park figure for mechanical advance. Here's the engine combo:

355 w/flat tops, valve reliefs, .015 below deck.
RPM heads, 64cc, 2.02/1.60 valves.
Cam - 235/245 @ 050, 507/514 110 lobe separation.
RPM air gap, 750 vacuum w/Proform main body.

Second - I don't think I need that much vacuum advance, the engine was surging at 3500 rpm. I plugged the vacuum line and took care of that issue. My vac can has a ratchet tab on the back that I can decrease the amount of travel but at the expense of bringing in more initial timing. This isn't a daily driver but I still want to run vacuum advance.

Thanks for your input.

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79 Z28 Bought new, honeymoon ride, same wife, same car.

11* mech. don't sound right at all.

Most dist. are set up with 18-24* mech. With most HEI's in the 20-22* range.

You want it so you can give the engine between 8* and 16* and get your 32*-38* total. That away you keep the starter nice and happy

I'm thinking 11 degrees distributor, which is 22 degrees crank. THAT'S more like it! On a 350 you generally want 34 to 38 total degrees, which with that dizzy you'd want 12 to 16 initial. That starter should handle that easy. I ran a stock starter with 11.4 compression in a 400 sbc!

As for the vacuum advance, you're right on. You need to get an adjustable unit from Summit or Jegs, and set it to 12-14.

Yes, there is 22 degrees at the crank mechanical.

Set your base to 14 with the vac advance plugged, then connect the vac advance and see how it runs. If it surges at cruise it typically means it's lean on the jetting.

[This message has been edited by Rick WI (edited May 29, 2005).]

Thanks guys - this is an HEI setup. Rick, that's the way I set the timing, but I set 36* total w/o vac at 3000, all of the mechanical is in by then. I went up on jet sizes, no luck - the surging did go away when I plugged the vac can. I'm going to pull it and put it on a distributor machine so I can verify what I've really got. I put a cheap after market spring/weight kit in and probably got what I paid for. I have a timing tape around my balancer but I don't really trust that thing. Again - thanks for your inputs.

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79 Z28 Bought new, honeymoon ride, same wife, same car.