MSD advance springs

[Tom Kirkham]

Originally Posted by Ant

this theory might not work with my KC Nascar based engine being a bit bigger in the ports and camshaft, I dont envisage it will have much below 4000rpm, however I have been told KC does a good job of producing engines that pull quite well from 2500rpm up. Is there a tendency to have it coming in higher up on less streetable engines, as a 427 which I have owned pull better down low?

Actually with a lot of valve overlap you are in effect bleeding off the compression at lower RPM, so you could get away with more advance down low. You might even be able to get away with a locked out advance if you use a start retard... It is the stock engines that make peak torque at low RPMs that can't take the quick advance curves.

If you are nervous about detonation...

The guys who build 1,000 HP Honda Turbo engines use a "can" to listen for knock. A "can" is simply a copper tube bolted onto the engine block hooked to a rubber tube going to the drivers ear. In other words a low tech stethoscope.

[Andy Dunn]

100 years ago at the dyno we would work the distributor setting in reverse...most high-end small blocks want 30 to 36 degrees total timing. We would start conservatively and set the distributor based on high rpm, not idle, and try and find the sweet spot in the 30-36 range. On one 600+ hp engine I built...the power under the curve was identical all the way from 30-36 total advance so we could leave the total on the conservative side of 30.

Generally speaking you get detonation at the "top" of the rpms, not at idle, so the low end of the curve doesn't matter that much. You want to prevent banging the engine up high in the 3000-7000 range. On the dyno, even if you can't hear detonation, you totally see it on the graphs. One tip from engine masters competition is...always get your dyno operator to check total power under the curve...peak power means nothing...total area under the curves mean everything and Superflo Dynos and others can easily calculate this.

I always ran the lightest springs (I think they were the thin silver ones?) and the dyno operator agreed since we want to get up to max timing, sooner rather than later. In some competition, people even lock the MSD distrib open but there is no need for that. One problem I found with "light" springs is that sometime the fly-weights can get stuck and not spin open. Check inside your distributor that there is no plastic flicky pieces or anything that would stop the fly-weights from opening. I think I remember we remedied the situation with a little silicone on the plastic pads that sit under the two fly weights.

I just found some old pics on the issue...sometimes the red cap top is not properly clearanced. If you tighten it down too snugly, it can catch the fly-weights. You can flip the red cap upside down and clearance it a little with a dremel. Here are the plastic pads that I used a small amount of silicone on. If you use the thick springs, none of this is an issue but if you like the fast full timing of the small springs, it is something to think about.


Andy

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