440 timing and pinging

[Outsider]

Glad you're seeing an improvement. Years ago I used to have a Sun distributor machine, but sold it when it had seemed to have sat for a couple decades. When I had time after retirement again, I did about 4 distributors in last couple years with the car sitting in the driveway with a tach meter in the engine compartment, a timing light and paper on a clip board to record the timing at the various rpms, and then changed the springs until I got what I thought I needed. Then I took it for a test drive going up a hill to put an additional load on it, judged the power by the seat of my pants, and listened for ping.

Did you map the rate the timing comes in at 500 rpm intervals and run it up to 4k or so, to see when it's all in? I ask because most of my big blocks like 16 deg initial or more, but on pump gas don't like much more than 34deg total mech. And after you figure it out without the vac adv, and then hook it up, often it is only better as the vac adv only adds when the load is low and the vac is high.

 

[451Mopar]

I think Geoff was asking about engine temperature and the Intake air temperature?
If your running a 180-190 degree thermostat, you could try a lower temp thermostat.
Not sure of a good way to get cooler / fresh air to the carb with the flat hood. Seems most of the intake air is going to be heated coming through the radiator?

 

[Geoff 2]

451,
Actually I was being more general with the 'heat & load' comment. Trying to get people to think about it....

Pinging is probably less or not there on a cold wet night [ heat ].....
And it doesn't ping in neutral [ load ].....

 

[dstuckmann]

Thanks for all the input. The pinging was less at night and cool days as expected, but still there under load. The engine temp stays a bit under 180 but there is no nice way to get cool air under that flat hood and still maintain a somewhat stock appearance. The car is a cruiser wih the occasional need to smoke the tires so the goal here was to eliminate the need of adding octane booster or race gas to eliminate ping. It's running pretty nice now with no ping regardless of load or RPM. That being said, I still need to do further testing when it warms up some more as the outside temps during testing have only been in the 70s. Turns out that the old Craftman timing light was working fine with the multi spark MSD but the bulb was quite dim. The new light with bight bulb, tach and advance, really simpifies things though. Here is where the car is at now.

Timing with VA plugged.
800-2000 - 14
2500 - 20
2800 - 27
3000 - 30
3200 - 34
3500 - 34

I tried finishing up by adding manifold vacuum for the VA but the idle speed was a bit erratic. I'm guessing this is due to the cam and slight variations in engine speed due to load (trans in gear vs park) and other factors (like engine temp) which really affected the available vacuum which in turn changed the VA and idle speed. Putting the VA back to the ported source really smoothed things out.

Again, thanks for the help and a special shout out to Outsider who gave me some numbers to establish a starting point for a street machine.

 

[lilcuda]

451,
Actually I was being more general with the 'heat & load' comment. Trying to get people to think about it....

Pinging is probably less or not there on a cold wet night [ heat ].....
And it doesn't ping in neutral [ load ].....

Your original post says that heat and load are the enemy of detonation. It’s actually the opposite. They contribute to it.

 

[Geoff 2]

If you want detonation, invite heat & load. It is the enemy.....

 

[T Brashears]

Sorry,didn’t realize that would happen. Can I fix it?

 

[biomedtechguy]

You MUST achieve ZERO "pinging" otherwise the engine is DOOMED. I can't stress that enough! A chat with Don and the FBO ignition system with "all in max advance limiter" would be SO MUCH BETTER than what you have, because you could run more advance at idle which is NIRVANA for a cammed up 6bbl, without exceeding the max advance that can cause pinging, and have a gradual curve. You can use the vacuum advance too, which you really should, and get a rev limiter as a bonus.
Regardless, you MUST get to ZERO pinging!

 

[Geoff 2]

The above is not quite correct. Technological advances, better sensors etc, have allowed engineers to better study detonation & pre-ign. Below is page 3 from an intensive study done on the subject by GM engineer Allen Cline, in 2000. As you can see pinging engines can survive 000s & 000s of miles of driving. No, it is not optimum, & nobody likes to hear pinging.
Another finding was that the pinging noise is NOT the collision of flame fronts as many believe, but the engine structure vibrating at 6400 hertz.

 

[biomedtechguy]

I appreciate the article, but I still contend that ZERO pinging is a goal worth working to achieve.

 

[RemCharger]

I appreciate the article, but I still contend that ZERO pinging is a goal worth working to achieve.

Biomed you're a 100% correct.
The plan you're on with computerized ignition is the best. Inputting proper data is paramount.
Old systems based on advance with vacuum input from manifold are only easily tunable with stock cui and size.
They actually work well in a base situation.

 

[GMP440]

Yes I read all the posts and do my best to take an "average" to come up with a starting point. The new distributor is installed with one black and one silver spring. Set initial timing at 16 without VA using the old timing light (a new one is on the way) and the car is soooo much better already. Still a slight ping so I'll try backing off the intial a bit and may take a bit off the total mechanical. Then see how VA comes into play. I'll keep you posted.

I agree with backing down your initial timing. I would even back it down to 5 degrees BTDC, see if you have pinging; if no pinging, keep going up on your initial till you hear the pinging. Someone mentioned earlier you might need to use different advance springs in the distributer.

 

[Geoff 2]

Stiffer springs in the dist will be preferable to retarding initial timing: for both performance & reducing pinging.

 

[biomedtechguy]

I have had my 440 6bbl Roadrunner for about 9 years now, and getting a good idle was a very important thing to accomplish for reasons beyond performance. With the idle in the 800s to 900 RPM range, the sound and feeling of rolling in to a car show, cruise venue, or in the stop and go traffic of Cruisin the Coast, with the lope of the Purple Stripe 292°/.509 cam and the electronic cutouts open is truly one of my favorite things to experience and share.
Being able to run more advance at idle because of the limiter built in to the FBO ignition system really allows for a great performance experience.
Soon I will install the Progression Ignition system, which I consider the ultimate ignition for a carbureated engine, and have all of the benefits I have now and when I turn the AC on the extra couple of degrees of advance I will set up in the advance "map" will keep the idle speed in the range I want without having to have it idled up the rest of the time to compensate.
As I read about springs, weights, the compromise "solution" of locking in timing and all of the other compromises required for any ignition other than Progression, it further reinforces what a great idea has been implemented in the Progression Ignition system.

 

[hunt2elk]

Lots of good advice so far. One other thing that was happening to me with a MSD distributor once. The shaft was riding up starting at about 1800 rpm and adding 10 degrees of timing. A $2 bushing on the shaft fixed it.

 

[PlymouthMakesIt]

That engine was not designed to run on unleaded fuel at the stock compression ratio, burning 100LL or racing fuel mixed with pump premium is your best bet to 100% stop pinging. Nothing beats tetraethyllead at smoothing the burn rate of gasoline.