Hi Lads,

I know this must be a pain in the **** by now. i currently have it timed to 14 initial/34 at 3000. However i'm missing quite a bit of ooomph (runs like a good stock 289).

I am deaf to ping (i just can't hear it). would it be a valid suggestion to run 10 degrees and measure g-forces in 3rd gear floored at 30mph all the way to 80, do the same with 12, 14 ... and go like that? See where it runs best?

what I figured as well is that when I keep advancing more the car is way more responsive when revving quickly in idle. but ya, there's no load. would higher load need less timing or more timing? is there any rules like: use what works bets in idle and retard 10?

well you see i'm desperate *g*

 

I worked my way through college with the GI bill and a Sun Distributor machine curving distributors for $10 a throw, so I have LOTS of experience curving distributors. The problem with my experience set is twofold; That was almost 40 years ago so I don't remember everything that I learned AND the fuel at that time consisted of higher octane regular than what we can buy at the best Premium pump in town today.

All that preface behind me, the curve that you have sounds really good to me assuming that your 34 at 3,000 is the centrifugal limit.

Yes, generally speaking, higher load will involve less timing. That's what the vacuum advance is all about.

I think you are on the right track in trying to come up with some measurable parameters and approaching it scientifically. What I might suggest is a knock sensor although I'm not sure how you would read the output from a knock sensor with anything except an oscilloscope. I'm wondering if you might come up with a circuit that would blink an LED upon the knock sensors activation, or possibly an analog meter would quickly swing upon a pulse from the knock sensor.

My 88 Vette has a knock sensor screwed into the block in place of one of the pipe plugs normally used to drain the coolant. I expect that it is a standard 1/4" pipe thread. To test the knock sensor on that car you strike a blow with a hammer on the block near the sensor.

Another indicator that you should be watching for is simply reading the spark plugs. SERIOUS detonation will put aluminum deposits on the spark plugs. This is of course from the piston tops, so it is a serious situation. As I recall this will only happen when you not only have too much ignition advance, but you also have a relatively lean fuel/air mixture. I'm sure that you are aware that fuel/air ratio and ignition timing have significant interaction.

I hope you find these ramblings useful. Keep us posted.

 

i never had alum (shiny) deposit on sparker. would scare the crap out of me. But i brought them to a peppery black stage once which already suggests knocking.
Problem is that now I don't know how long it would stay there (the pepper). maybe I should use a set of a new sparkers and start from scratch.

Obviously A/F makes a huge difference to it as well. Maybe I should just leave ignition at what it is (it sounds reasonable) and just go and check if I can improve A/F. I would be well surprised if that is still correct after changing from half damaged cam to a new one.

 

Kalli,
One way to definitely hear pinging is to drive over a bridge or something with high sides, concrete, guard rails, etc... and you will hear it. It also works well since you most likely be going up hill.
Pinging isn't good, but it may put you more at ease to hear that even with some bouts with detonation last year, my piston tops looked normal when I changed my heads.

 

kalli,

Do you get any surging, even very light surging, at cruise? That would be consistent with what you were explaining and would, of course, indicate that you might need to fatten the main jets one size.

 

i'm going to go and drive her tonight and check on plugs again, attach the A/F. for the moment I have my money on pig rich. no surge anywhere. well behaved and slow ;-)

 

I didn't realize that you have an A/F analyzer. I'm too stingy to buy one. What I do is MIG a bung in the header pipe and put in a cheap, one wire O2 sensor and then use a DVM.

One more tip which may very well be of no interest to you since I doubt that you are a tight wad like myself. When I'm going through this process, instead of replacing plugs for spark plug reads, I just clean them with a cheapie spark plug blaster. This gives me a fresh plug for reading. After the tuning process is complete, THEN I screw in a new set of plugs.

A warning about plug blasters. They use glass beads. I will not blast a wet plug with glass beads for fear of a few of them not getting removed and making their way into the engine. The beads are too small for the oil filter to catch. Blasting a dry plug is no problem and the beads will come off easily by blowing with compressed air.

Keep us posted.

 

cool idea :-)

 

Kalli, I had some detonation issues last year that came pretty much from running too rich at WOT. Once I got a handle on the AFR, my detonation issues basically went away. Follow the AFR. It does not lie. Max power is going to come around 12.5-13:1. The best fuel efficiency, for me, is low 14s b/c anything higher causes lean surging. I can really tell when I hit the secondaries because my AFR goes from 14s to 12s and my power kicks in like a nitrous hit. If your all your plugs are firing (a misfire will show a leaner AFR...crazy I know), then make sure your AFR is set right throughout your throttle movement and under load and cruise. Once you have that set, get a friend to drive with you that can hear the pinging and do some WOT pulls. You can increase the timing a little bit at a time and then do another WOT pull. Stop when your friend hears the rattling marbles. IMO, AFR is going to affect your performance MUCH more than a few degrees of timing. I consider timing adjustment, fine tuning.

 

Detonation from a too rich mixture?