408, pumpgas, EQ heads, 10.1 to 1 compression, liked 30 degrees max on the dyno. Cam is a Comp Thumpr 235/249/107 in at 105, airgap intake. It is at 14 initial now to get it back to 30 total in by 4,000. My converter flashes above 4,000. I am thinking of going to 20 initial plus 10 for 30 total to help idle and cold starts. Ideas?
Initial lead? 408, pump gas,
- Thread starter gregsdart
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j par
Well-hung Member
I have a very similar cam with iron heads and a little more compression on pump gas and still running about 35 degrees total is about 23 initial. I'm a little surprised that 30 all in is where you're at. But I know every motor runs better at a different spot.
20 + 10 mechanical should get you in the ballpark of decent/better idle quality.
If it's a driver, i'd get the total in way before 4K unless you have vac advance on it pulling 14*.
If it's a driver, i'd get the total in way before 4K unless you have vac advance on it pulling 14*.
Fisher
Old Guy with a Cool car.
In my experience, most performance engines respond well to lots of initial timing I have 20 initial on mine with 32 total all in by 3000 rpm. 3500 stall flashes to 4000 no detonation.
furrystump
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I think you’ll be fine, I run about 25 intial and 34 total all in at 2500. With 12.2 to 1 any more and it tries to kick back on starting.
fishy68
Tyr Fryr's Inc.
Since you need 30 total 20+10 all in by 2k should work fine IMO
mderoy340
Well-Known Member
If your carb is good for idle and off idle transition set your initial timing for best vacuum and idle quality in gear. Heat soak the motor and see if the start is good. Back off slightly if kick back occurs. I run my 340 10.5:1 RHS LAX heads at 28* initial 34 total on 93 pump gas. After you get the mechanical timing setup move on to vacuum advance. I run ported vacuum starting around 6" of vacuum, every motor is different and it's time consuming to get it right.
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