What advance curve, straight line or hop out?

812 Views 3 Replies 4 Participants Last post by jbird, Mar 21, 2007

darkostoj

Discussion Starter · Mar 14, 2007

I just got an advance tuning kit for the mallory dist. I have had a hard time getting the motor running right so I figured I'd tune the dist properly. First of all here are the specs on the motor.

355 chevy
10-11:1 compression, not sure
camelback heads
long tube headers
a pretty lopey camshaft, don't know the specs though
weiand tunnel ram intake
dual holley mech secondary (9776) 450cfm carbs
2800 stall th350 trans
10* vacuum at idle

I was going to set the timing at 18* inital and 38* total. The tuning kit says I could either set the advance to come in as a straight line where a smooth linear advance is required throughout the engine operating RPM, or a Hop-Out curve where a lot of advance is required early and a more gradual advance through the rest of the engine operating RPM happends. Is one better than the other for my application? Does 18* inital and 38* advanced sound like a good spot to set the timing?

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SWHEATON

· #2 · Mar 15, 2007

18 initial & 38 total is the perfect spot to begin dialing in a perf motor.

You can tweak the initial & total a little from there but the 18 & 38 is a very good place to start & very close to or exactly where many motors endup after the dialing in process if over.

As for when & how quick the mechanical adv comes a general rule is all the mechanical advance should all be in by 2,800-3k rpms . But with your tunnel ram & dual carbs i would have all the mech in by 2,800 for a little better bottom end power.

Also,with dual carbs on a tunnel ram there is usally alot of tweaking & or dialing in that is required to get them working correctly for best perf too.

Scott

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