[Ron Sutton]

I hope I'm not taking the focus of your thread off track. There is an idle challenge & an idle solution when putting race engines in street cars.

The challenge is, with full on race engines, the duration of the cam is quite large and doesn't want to idle well. This is compounded by trying to run initial timing (meaning the amount of timing advance at idle) in the 8° to 16° range. The lower you try to run the timing, the harder challenge the engine has trying to idle. If the engine is carbureted, the challenge is compounded. If you adjust the throttle blade position open enough to get it to idle ... this is often so far it uncovers the transfer slot ... which adds more fuel ... making the engine run rich & idle poorly ... requiring the throttle blades to be opened even more to stay idling.

With this arrangement, you find the engine is super temperature finicky, hard to keep idling ... and loads up the spark plugs with fuel. So you put in 2-3 steps hotter plugs to prevent that. Now the engine is more susceptible to detonation. So you retard the timing more ... making the situation worse.

The additional PITA is how poorly this combination takes off from a standing start. Automatics aren't too bad, but the manual trans cars have to slip the clutch & rev the engine to get their baby rolling.




Before we get to the solution, we need to embrace five facts about engines:
1. Engines require a certain amount of power to spin the rotating assembly. How much varies with component weight, friction, valve spring pressure & compression. Let's call this rotating power loss.

2. If the engine doesn't make enough power ... at a given rpm ... to overcome this rotating power loss at that same rpm ... the engine dies.

3. Larger duration cams ... especially the durations in full race engines ... shift the power curve to build more power in upper rpm ranges & reduce the power in lower rpm ranges. The lower the rpm, the less power they make. So idling at 1000-1500 rpm is a challenge.

4. Advancing timing ... to a point ... increases engine power & torque. Reducing timing decreases engine power & torque.

5. We need more power & torque at idle rpm with big cams.



The solution is more timing at idle. Not a little more. A lot. Frankly the engine needs more timing at idle that at any point. If an engine builds best power with 36° of timing ... it needs a little more than 36° of timing at idle. But that 's not always feasible.

So why didn't factory engines come with lots of timing? Too hard on the starters. So they used vacuum advance to advance the timing at idle ... to help idle & low speed take offs.

And full timing ... say 36° ... it death on starters. Even if you buy the bad boy, double throw-down, mean, hi-torque, gear reduction starters ... 36° of timing ... when turning the engine over to fire ... will shorten their lifespan.

The starter solution is to utilize a timing retard when turning the engine over to fire. For distributor ignition systems, I LOVE the MSD E-Curve billet distributor. While it has a lot of possible timing curves, it also has the feature we need with these engines ... which is locked timing with a start-retard feature. This is a well designed distributor with billet body, shaft bearing instead of bushing & solid state electronics. No MSD Ignition Control/Amp is required. You can run one or not. You can run a vacuum advance if you desire too, but that's not usually done on race cammed engines.

In my 730HP SBC race engines, we ran the MSD E-Curve with 36° total timing ... locked in all the time ... except when starting. The E-Curve distributor has a built in start/retard option ... that when selected ... allows us to retard the timing up to 30°. So my engines started with 6° timing.

Man ... I'm telling you ... with 6° & a good starter ... they fire instantly. As soon as the rpms exceed 1000, the timing goes to full advance ... which in my case was 36°. The engine purrs at idle. It's crisp & easy to tune. The engine responds amazing when revving off idle. The car takes off easy ... preventing embarrassing moments ... and saves clutches.

There are three easy ways of doing this.
1. Utilizing a distributor with this feature built in, like the E-Curve
2. Adding a starting retard module to your distributor ignition.
3. If you have a distributorless engine, like LS & other modern engines, program this into your timing controller.