Distributor for Boost
If I was going to run more then 6 pounds of boost I would just lock out the distributor and run a programmable ignition and tune for boost. Right now with only 6 pounds I know that I can get away with an almost stock distributor. I am almost tempted to just lock the distributor fully out at 28 degrees since it is not a daily driver but then I run into rough idle and hot start / rough start problems.
Drag cars run locked out fully advance distributors all the time but they do not have to worry about idle issues. If I could get my initial timing somewhere around 14 degress and have it fully advanced 28 degrees by 1800 rpms then I would maybe only have a slightly hard start.
I have a partner in building our car, so if I say "I," I really mean "we" because we talk everything over before we do it, so a lot of the things that get done on our car are a joint effort.
Our car is basically a higher-boost, strip car with little time planned for the street.
What have learned is (and, bear in mind, this applies to OUR car; not necessarily yours):
1. Flame fronts travel a lot faster across the piston under boost than they do in naturally-aspirated engines. We built a copycat engine that was based on two 500hp high-boost (25+psi) motors, both of which run a MAXIMUM of 18 degrees total spark advance.
So, what I did was to acquire a Lean Burn distributor rhat has NO spark advance mechanism of any kind; no mechanical, no vacuum.
We set total advance at 18 degees.
The car runs great on the street with this setup and never kicks back on the starter.... starts easily, every time. Idles like a stock /6.
When I say "runs great," I mean that the street driving that we do has us watching the boost/vacuum gauge and we keep it OUT OF BOOST
all the time, so as a normally-aspirated engine, it doesn't appear to need more timing than the 18 degrees we give it. I know that sounds weird, but it is what it is...
If you are dead-set on running a curve, MSD makes a device called a "Boost Timing Master" that will retard your spark either one, two, or three degrees (your choice, set from a knob on the dash) for each pound of boost it "sees," up to a maximum of 15 degrees. I have one on my other car (a Vortech-supercharged 360 Magunm,) and it works as advertised.
That Boost Timing Master has an analog spark module that generates 42.000 volts. Plenty for my car with 10 pounds of boost. With only 6 pounds of boost, timing should not be critical on your engine, I would think.
Good luck, and I hope you get this issue settled to your satisfaction!:blob:
