Induced timing retard @ top end - Chevelle Tech
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post #1 of 11 (permalink) Old Dec 22nd, 04, 3:07 PM Thread Starter
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I recently purchased a MSD Digital 6 ignition box which has the ability to retard the timing. I don't run NOX but the possibility of retarding the timing @ top RPM interests me. I could use the RPM signal from my delay box to send a signal @the upper end of the RPM curve to retard the timing. Is there anything to gain here?? Does anybody have experience with doing this ???

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post #2 of 11 (permalink) Old Dec 22nd, 04, 5:23 PM
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Use ta do the same thing by shutting down one set of points in a dual point distributor. It was worth about 7-8 hundredths and about 1 1/2 mph on a low 10 second 125 mph D/Altered car.

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post #3 of 11 (permalink) Old Dec 22nd, 04, 5:51 PM
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Was thinking about using the MSD 8982 2step retard in conjunction with my MSD 6AL box. Any one used that box before?

Dyno John,

I currently am running 39 total advance, and if I end up using the box running 42 total and then retarding it at the top end..how much retard is good to start with?
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post #4 of 11 (permalink) Old Dec 22nd, 04, 6:49 PM
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As I recall we would get about 4 degrees retard. It depended on how the points were adjusted. We would drop the timing back when we hit 4th gear. It was definitly worth doing.

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post #5 of 11 (permalink) Old Dec 22nd, 04, 10:15 PM
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How does retarding the timing help? Can someone explain this to me?
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post #6 of 11 (permalink) Old Dec 22nd, 04, 11:36 PM
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When the car goes into high gear the gear spread from the previous gear is usually more than the between the others so the rpm drop on the shift is greater, also the engine is under more of a load at that point and needs to have some timing pulled out- at least that's the way I understand it. Maybe someone will correct me. It's called a high speed retard not high rpm retard.
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post #7 of 11 (permalink) Old Dec 23rd, 04, 11:05 AM Thread Starter
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Baddbob, good point.So using an RPM switch may not be the best idea as I may want to switch it when I enter 3rd gear. Has anyone set one of these up other than for Nitros?????

67 Chevelle Drag Car 3348 # w/ driver & 30# ballast 522 BBC N/A, Turbo 400
Wolfe Craft rear antisway bar and control Arms,4.10 spool 10.5 x 28 MT slicks, Pulling 615 H.P. to rear wheels on chassis dyno.Best run 1.346 60 ft, 9.524 E.T. @ 141.54
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post #8 of 11 (permalink) Old Dec 23rd, 04, 11:08 AM
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Not that anyone cares, but the OLD GM electronic ignition box from the '60's would pull out one degree for every 1000 RPM.
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post #9 of 11 (permalink) Old Dec 23rd, 04, 11:30 AM
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Quote:
Originally posted by Fried_Guy:
How does retarding the timing help? Can someone explain this to me?
It may have more to do with the rate of acceleration in high gear (slower) and preventing detonation (which will rob power). I think my car spends ~7 seconds in high gear on a mid 10 second pass That only leaves 3.5 seconds for 1st and 2nd, so the rate of acceleration is proportional to the gearing. The longer the engine stays at a higher RPM (more load) the more heat it will build.
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post #10 of 11 (permalink) Old Dec 26th, 04, 10:42 PM
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It's worth playing with. I did the same thing years ago on a mid 10 sec Nova with tunnel ram 396 and 4 speed. Had to use TONS of timing to get it to have any throttle response at all with cam. intake. 660's and rectangular port heads. I used a toggle switch on the second set of points to start retard just after the 2-3 shift and it really liked it!

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post #11 of 11 (permalink) Old Dec 27th, 04, 4:23 AM
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Throw it on a toggle switch, by your shifter and start playing with it at the track making no other adjustments at all.Record your data and let me know cause i have a digital 6 and bought it for the same reason...the 2 RPM limiters and the top end retard.
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