Timing Tuning Philosophy

[kalli]

just on a note: switching engine off after WOT run. I'm aware I can't drive 5 miles home to check on the plugs then, but realistically I can't switch off the engine at 90mph (which would probably clean the plugs with petrol anyway) So would a normal run and slowdown stop be valid as well. let's say get up to 90mph, slow down in a normal fashion to a stop and then pull the plugs? i don't need a quote here, but I always wondered how long it takes for a plug to change appearance? btw: i ordered the reader/DVD you mentioned earlier on. Can't wait. will be very interesting stuff I'd say Kalli

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[urban_cowboy]

I understand the idea of checking plugs and WOT pulls to set total timing, but the shape or aggressiveness of the curve is what has been scratching my head. How can checking plugs tell you if you need to have your timing hit full advance at 3000 or 4000rpm?

On a performance motor with a rowdy cam, high compression, a rich (12.5) AFR, and a torque curve peaking later than stock, do you want a faster timing curve with timing coming in lower in the power band or do you want to delay the timing to hit closer to peak torque?

Edit: Kalli and 67mustang302, what reader DVD are you talking about?

[kalli]

http://www.pro-system.com/sparktool.html
supposedly the DVD is good info. I have read a lot of articles about it on the internet and they are quite contradicting. So i thought I get it from that source and stick to it.
Some say the colorchange on ground strap will tell you about ignition, some other say this indicates the heat range only. i believe the first version as I was witnessing it change with timing settings. This way I hope to get some clarification

as to your question I believe trial and error and listening might be the best way to go. I rely on tools as I don't know what pinging sounds like. I'm good at recognising sounds that I know what they are, but noone ever told me: hear that. that was pinging. so I'm quite deaf to it :-(

[67mustang302]

The best plug read comes from a shut down right after WOT, but you can still read them sometimes after driving on them, it's going to depend on a bunch of factors. Generally though, reading them after running on them is less accurate.

As far as curve, general rules of thumb are the higher performance the engine is, the faster the curve, the lighter the car, the faster the curve, the better the gearing, the faster the curve.

Just a for instance, mine is at about 14 at idle and 34 total by 3,000rpm or a shade under. The timing curve adds 20 total, advance starts at 1,000rpm and it adds 12* by about 1,200rpm, then the remaining 8* is added between 1,200-3,000rpm, till full advance(about 34 total) is in by 3,000rpm. It's a Crane digital curve dizzy. So the curve has 2 distinct "ramps" of timing being added. Which one works best is going to depend on engine configuration, chamber design, compression, cam, fuel, intake, exhaust etc. A lot of it is trial and error.

[THUMPIN455]

It depends on a bunch of things, not the least of which is how big the engine is, what compression it has, cam timing, and available fuel quality. To find out what it likes the best takes trial and error, some engines can withstand more than others in different conditions. Too far in either direction causes different problems, like heat, surging, low power, or limited power on the top end, just depends on what the engine wants.

Take the time and find out what your car wants, take it to a strip and find out what it wants for best power. Drive it around on the street and find out what works best as far as advance curves, initial and total timing. My low compression 455s like to have all the advance in before 2000 rpm, and they like between 36 and 42 total. The high compression 455 I ran a few years back needed more advance because of the chamber shape the heads have. It ran 52 total all in by 2000. The low squeeze engines also run 1900-2200 stall converters and make 500ftlbs just off idle. The 302 that was in the Cougar didnt like that much that fast, and if it was advanced too far at cruise RPM it would surge and run funny.

They are all different, it takes some work and experimentation to find out what works best. General guidelines are a good place to start, but a blanket this is all that will work isnt always correct.

[67mustang302]

+1

Every combination is just a little bit different. What's good for the goose isn't always good for the gander.

[urban_cowboy]

I pulled 6 plugs yesterday (the other 2 were just too hard to get too) mostly because I notice a wet tail pipe on the driver side. I also wanted to check on my plug colors. I found one plug that was pretty oily and grey...I thought I felt a little drop in power but not really a miss. I had some crazy rich issues with the other carb, so I am going to give it the benefit of the doubt and just replaced it with a new one. The other 5 plugs I pulled looked pretty good. They were all consistent in their coloration and were a light tan. The ground strap shows a color change just before the curve or apex. The plugs look to show some slight signs of detonation, which confirms what I hear. It is raining now, but I plan to take a degree or two of total timing out and run it when things dry up. I can then pull a few plugs and check for changes and check that bad cylinder...gosh I hope it is just a fluke fouled plug that could not clear up from the old carb and not a ring or valve stem seal issue.... If the new plug does the same thing, I will put a pressure test on it to compare two cylinders...I guess it good news that none of the plugs were chalked up black nasty things like they have been in the past. I guess that means I have my fuel curve close .

I think I will run another can of BG 44k in this tank to really clean things up. I really like the BG 44k and BG 109 oil cleaner additive. If you have not tried them check it out. It appears to be pretty good stuff.

[htwheelz67]

Timing can be a pain sometimes just like carbs, I'm looking at the msd 6al2 programmable ignition, you can dial your timing curve with a laptop and use a map sensor for vac advance/boost retard, it has burnout rev limit, launch rev limit, step and high speed retard, start retard, boost or n20 retard its expensive but what a great tuning tool.