How much timing is too much?

[mac99]

Timing in my 383 stroker is up to 34 degrees in the high rpm range with no retard...is this too much???

[SSpdDmon]

The answer to your question is application specific. The real way to tell optimal timing is to get some time on a dyno and do about 7-10 pulls. Adjust timing until you find peak HP. Some motors will take more timing without making more power or detecting any KR. So, the whole throw timing at it until you see KR theory is pretty much bogus.

[jimmyblue]

Your peak output will be fueling -and- spark dependent.
More fuel needs / wants / tolerates more spark. Over-
rich will let you put down a lot more advance, but you
might find more power from leaner mix than from more
spark.

Everything I've found says that for any given mix your
MBT advance will be 2-3 degrees before onset of ping.
So this is how I dialed in mine. First getting the WOT AFR
to be 12.7-12.8 (maybe not totally peaked out but a bit
on the safe side), then d!cking the spark table around
ad infinitum using the max retard histogram, adding 2
degrees anywhere I got zero KR and subtracting 1 where
I did. Then, when I got the histogram close enough to
1 degree max KR all over the place, I took 2 (or was it 3?)
out of the timing table across the board and called it good.

But how good, I have no before/after data. So... ???

Stroker motors, long-rod and so on may have a different
degree of spark tolerance than original-geometry ones.
So too, compression, cylinder filling/scavenging, other
things that affect peak pre-spark pressure and the rate
of pressure rise vs the rate of cylinder expansion w/ angle
(time), will affect where optimum spark-point lies. Cut 'n'
try, basically. Knowing no better, I'd say stay 3 degrees
short of ping. But to do that you have to step in it once.

[mac99]

Thanks for the help guys!

[tici]

The answer to your question is application specific. The real way to tell optimal timing is to get some time on a dyno and do about 7-10 pulls. Adjust timing until you find peak HP. Some motors will take more timing without making more power or detecting any KR. So, the whole throw timing at it until you see KR theory is pretty much bogus.

Agree! we went up from 17* to 23* and saw no more power at all (supercharged).
No KR and those are measured values (not what I set in the PCM).
Funny because everyone tells about increasing timing with a blower will "dramatically" increase the power... :
We also messed around with the AFR but nothing.
Car has an alkyl kit (theoretically allows more timing and more "power&quot
... as you say: BOGUS!

[Synergy]

Its all in the camshaft. Every camshaft will reach a point where you can add timing but it does nothing. The key is to be right where you are firing at peak cylinder pressure and no more no less. Then you can do the rest with fueling.

Rick