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Old 05-12-2011, 09:57 PM
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Tuning MSD Mechanical Advance Distributor

Engine:
385 sbc Scat 4130 bottom end Scat I bean w/ 7/16 bolts
Probe SRS .040 flat tops with reliefs, block decked to 9.08"s
Standard oil pump with cheapy Moroso with wings no windage

Solid roller: Comp Xtreme Energy XR280R Duration 280/286, Lift .570/.576 (with 1.5's, I've got 1.52 comps..

Dart 230cc Iron Eagles ported with a Air gap single plane and Holley 850 dp

I built this thing at the local CC and it's all tight, right and new

My question is I've got a MSD pro billet non vac distributor and want get it dialed in. I'm running 24*-26* idle timing per this "run on" thread post #16
New built 385 SBC Dieseling

The dist has the 21* stop in it now and two of the heavy silver springs in it per factory MSD settings. So I'm running like upper 40 something all in timing. On the dyno with the same stop and springs it pulled 489 with 38* all in..

What I'm thinking is going all in by 3000rpm with a light silver and a light blue spring combo and using the largest stop I have which is 18*.. That will still have me in the 40* range.. What I need is a 12-14* stop to put me around 38* with 25* off idle..
Does this sound right? Can I use a tiny washer to make the 18* stop larger while making it a 14*er?

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Old 05-12-2011, 10:02 PM
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Oh and I'm guessing I've got a 3500 stall in the TH350 and 4.56 out back..
Here's a quick little vid to give you an idea
http://www.youtube.com/watch?v=_KZp_rmUzVM
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Old 05-12-2011, 10:13 PM
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oops, just saw in the MSD directions how the diameter of the spacer is what sets the stops. So I guess I'll turn one on the lathe then. I'll measure each one and divide it by it's * setting and then add them up to 10* and 14* for my total diameter. What about my all in at 3000rpm theory with the blue and silver light springs?
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Old 05-13-2011, 12:05 AM
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Just found this little bit of info. What do you think?
http://www.4secondsflat.com/MSD%20Di...r%20Tuning.htm
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Old 05-13-2011, 01:43 AM
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I have a motor similar to yours, with a bit more duration (248/254). I feel your initial timing is excessive. I have mine a 18 with the 18 stop all in at 3000 making over 550hp. Idles at about 900.
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Old 05-13-2011, 02:01 AM
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Quote:
Originally Posted by hotrod937
oops, just saw in the MSD directions how the diameter of the spacer is what sets the stops. So I guess I'll turn one on the lathe then. I'll measure each one and divide it by it's * setting and then add them up to 10* and 14* for my total diameter.
I think $33 plus is too much money for a pair of bushings, but they would give you what you're looking for. I'm not sure if their bushings are a "drop in and go" deal, or if the larger diameter of their bushing requires the slot in the distributor advance plate to be widened. The reason I mention this is IIRC, someone had said the bushing would need to be ovoid to fit into the unmodified slot if the bushing was sized to limit total mechanical timing to much less than 18. You can inspect yours to see what the case is, I'm sure- and if you can make your own bushing, by all means do it and save some cash.

Quote:
What about my all in at 3000rpm theory with the blue and silver light springs?
Convention holds that total timing all in by no more than 3000 RPM is desirable w/a performance SBC build, sooner if the engine combo, fuel, conditions, etc. allow for it. As for what combination of springs will give you this, I cannot say. It's basically a trial and retrial deal.

Also, that cam may well want more initial timing, but again it's try and retry to see what the results are- there's no set law on how much initial timing or how soon the total is in by, when dealing w/ignition timing. Too many variables. But high 40 total is way too much, as you know. I'd shoot for somewhere between 34 and 38, depending on the heads, fuel, etc.

Quote:
block decked to 9.08"s
I'm guessing you mean 9.008"?

Good luck.

Last edited by cobalt327; 05-13-2011 at 02:06 AM.
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Old 05-13-2011, 07:21 AM
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If you want you can stick something in the end of the slot to shorten the travel further, while using the biggest bushing in the kit.

This will allow more initial at idle. Something in the 20-26deg zone should work well)

Try it locked out, first, just for grins.

+Make sure the amount of vacuum advance is not excessive (10-15deg max @ high manifold vacuum part throttle)

and that it comes in and out at the right rate.
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Old 05-13-2011, 11:48 AM
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There is no vac advance. I have another MSD that has the vac advance tho.. Maybe I'll lock that one out and try it.
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