High Speed Ignition Retard

[distributorguy]

With my experience rebuilding distributors and testing advance curves multiple times daily, I can agree that timing retard truly depends on a lot of motor factors, such as dynamic cylinder pressures, fuel, and of course combustion chamber shape.  Most of the time, a distributor WILL retard at the top end, whether you want it to or not.  That can be worked out by reducing clearances, using stronger advance springs, reduced shaft end float, and limiting the timing travel.  The flathead being a 3 gear system to drive the distributor (crank/cam/dizzy), there is very little backlash which is great.  The better the combustion chamber design, the less timing you have to run.  You could always try to run the Pertronix to trigger an MSD box with adjustable timing on the dash, but in my experience, the more layers of electronics you add, the more power you stand to lose at the plug.  If you're overpowered (ignition) already, then its ok.  If you're on the fringe, you'll see a loss.   Just be mindful of RFI and EMI.  Maybe use the retard knob while at the dyno to see what it nets you.  More likely than not, if retarding the timing makes more power, you may be too far advanced across the power band to start with?

[kiwi belly tank]

I really love the "turtle deck roadster ran into the back of a P-38 tank" look, it absolutely screams hot rodding.
That being said, you will find more speed addressing the aerodynamics. The air flow through that oil rig over the driver could be cleaned up by continuing the body work over it to make the air go around it. That's a lot less work than lowering the driver & the cage. A smoother blend into the engine cover panel without the step would be next in line then the transition of the engine panel on to the turtle deck could use some radius to help reduce separation or you could just continue it further back at the same plane to get a similar effect.
The turbulence off the front end could be reduced by going to a split wishbone instead of the hair pin & bat wing without losing that classic look.
A skinnier front wheel/tire combo will also help you find some more speed.
  Sid.

 

[Rex Schimmer]

I have to agree with Sid, you have a lot more potential "free" hp by doing some aero work than you will find with spark retard. Lowering the Cd has exactly the same affect as increasing the hp but it looks like your flathead is pretty much maxed out as far as what you can do to make hp but your body does have a number of areas that could be improved from the aero stand point and Sid has mentioned several.

Rex

[ronnieroadster]

Sid and Rex thanks for the ideas now I'm going to lose more sleep thinking about this stuff. Overall I'm pleased with the transition lines from tank to roadster now I will give thought to the aero. I was thinking this weekend I didn't have much to do on the car now IM going to be busy.
 Ron

[panic]

Significant difference between high RPM retard (as VE goes down, so does cylinder pressure) and high MPH retard (as the car hits the wall, RPM change begins to stall, maximizing load).
Some tuners have discovered that, rather than thinking of the best high speed setting as being retarded (although it's relatively retarded), what happened is that the original setting was correct for high MPH, but the engine would tolerate slightly more advance in the lower gears.

[ronnieroadster]

Significant difference between high RPM retard (as VE goes down, so does cylinder pressure) and high MPH retard (as the car hits the wall, RPM change begins to stall, maximizing load).
Some tuners have discovered that, rather than thinking of the best high speed setting as being retarded (although it's relatively retarded), what happened is that the original setting was correct for high MPH, but the engine would tolerate slightly more advance in the lower gears.

  That's interesting I know I'm very conservative on the timing.  Flatheads are not happy with to much timing especially blown on gas. The development of my present combination has proven its extremely safe this of course did not happen overnight. It took four years of experimenting to get the combination to the point where I no longer spend money repairing a damaged block, pistons or valves. But were always looking for more speed its an endless cycle.
 Ron

[hotrod]

You are also contending with heat soak from sustained high power operation. What would be safe ignition advance just a mile off the line, might not be safe after 3-4 miles of full power, when heads and pistons have reached their max temperatures. Some engines will need it some will not.

Many people tend to over advance ignition to get that last little bit of power but that makes for a brittle tune that has no margin for error or changes in operating conditions.
During WWII they did a lot of engine research on the aircraft engines and found that the safest tune for them to keep the engines alive during max power combat conditions was to find the max power setting for fuel and ignition on the dyno and then pull back the timing just enough that they could just detect a 1% power drop. That gave a small cushion that would keep the engine alive when it got pushed beyond normal operating loads and sustained high power operations at combat emergency power.