Boost Retard in Vintage Classes

[saltracer1]

Is boost retard "legal" in the vintage classes? Particully blown flathead modified roadster. What I'm talking about is the MSD electronic unit.

[4-barrel Mike]

Welcome!  Are you also on the MSN Flathead forum?

Change in the rules for 2007, says, in part concerning vintage engines: "Any ignition system may be used."

Mike

[saltracer1]

two flathead forums and the HAMB. Got our old car back and we are re-doing everything.

[dwarner]

If you plan to use a flathead in a roadster a turbo is still not allowed. If your turbo flathead is in any other non-vintage(post 1948) body the boost control is OK. I am not familiar with the use of auto retard on a roots blown engine, is this done?

DW

[JackD]

A simple vacuum advance is a boost retard that is not likely to be outlawed soon.

[dwarner]

Yeah Jack, but it doesn't have a fancy red box around it and two new stickers.

DW

[Don Brent]

I am not sure about your case but was told several years ago that I could not run a MSD timing computer on my flathead modified roadster and I took it off.  The box is different from what you are considering but the idea is much the same.  I wanted to use it to advance the timing (I was unblown using a crank trigger.) and you want to retard the timing.  Both are Red boxes that electrically use a input signal to control timing so fall outside the exception for data collection.  Probably not a big deal but I would count on at least one person I can think of putting up the $100.  I think you will lose.  Good luck, Don

[JackD]

Yeah Jack, but it doesn't have a fancy red box around it and two new stickers.

DW
[/quote   HUMMMM.I feel a merchandising moment coming on.

[jimmy six]

MSD 6AL boxes, Electromotive, etc are common place on vintage engines in vintage classes today. I'm not familiar with which MSD box was not allowed according to Don. Might be the 7 series and above.

As far as I know, something cannot be used which would be controlled by something else on the engine like the EFI adjusting by an O2 sensor. If the retard is set by RPM it has been allowed. Once the setting is in the "box" it happens when told and does not self adjust.

I would contact the guys who are running Blown flatheads and ask them...Good Luck 

[4-barrel Mike]

FWIW: from www.roadrunnerengineering.com who does street (mainly) blowers for flatheads:

Ignition Timing For Optimum Power and Economy
There is an optimum ignition timing for every combination of engine, fuel & operating condition. As blower and cylinder pressure go up, the engine needs less advance for peak power, so retarding the ignition is a good thing for power under boost. Retarding the ignition timing, either manually or automatically, is also often desirable to decrease detonation tendencies on supercharged engines, especially when using lower octane fuel. MSD (P/N 5462 or 6462) & others, provide automatic electronic boost retard modules for any ignition. Unfortunately, it is difficult to determine optimum settings without a dyno, so be conservative!

Mike

[rebelce]

"As far as I know, something cannot be used which would be controlled by something else on the engine like the EFI adjusting by an O2 sensor. If the retard is set by RPM it has been allowed. Once the setting is in the "box" it happens when told and does not self adjust. "


I think we need to find out what the SCTA calls a computer.   Just because it says "Timing computer" on the label, doesn't mean it really is.  We have "Turbo" aftershave, some things are just marketing verbage.

What would be the best way to determine this?

[4sfed]

Is boost retard "legal" in the vintage classes? Particully blown flathead modified roadster. What I'm talking about is the MSD electronic unit.

The Corvair turbo had a boost retard diaphragm.  It looked like a vacuum advance from the outside, but inside the spring was on the other side of the diaphragm.  Shouldn't be hard to make one . . . all mechanical, vintage legal.

-Jim