That is what I usually observe when checking timing with a locked distributor.
Timing
- Thread starter Ironmike
- Start date
-
pink340swinger
Well-Known Member
I tried it years ago before digital programable MSD ignition systems were invented. I had a switch on the steering wheel that I could flip and retard the timing to whatever chip I had plugged in. I tried 3-8 degrees if I remember correctly, didn't work with it a lot as I had a lot going on and was learning other things about my car, but it did pick up maybe 1mph, at best, never saw any E.T. improvement. I'm sure there is something to it and you probably have to make other changes as well. Guys use it all the time in comp and prostock, changing timing in each gear change, and the ones who really know what direction to go and how much aren't talking, at least the guys I have asked...
Are you sure you don't have this backwards?
Well I give you credit. You AT LEAST post the articles large enough to read. Unlike Bewy.
There is no indication of the closed chamber head in the literature, nor an aluminum head. There is about 6 pages on Ignition systems, but you get the point.
Is that a misprint? Should it read "12:1 - 35 to 36" degrees instead of "35 to 60" ?
What is the context to the test that says the same engine produced the same power curve with 2-3 degrees less ignition lead? was it a test between a point ignition and a msd gold box? The print is too small to read on the graph pictured.
I wonder if the timing curves shown are as seen on a distributor machine or read directly from the running engine on the dyno? It's interesting that the chart doesn't show any retard after the timing is all in. I can't read the print at the bottom of the chart but it looks like it skips from 1300 rpm to 4000 rpm and I can't read if that is distributor or engine rpm.
What I’m asking is you see less retard with rpm after a certain rpm?
That’s what I’m not understanding.
Yes, generally.
I agree somewhat with the part about being at least a bit insensitive to TOTAL TIMING but they are very sensitive to the shape of the curve.
As for the “fast curve” I’ll say what I always say and that is the timing will follow the VE curve very close.
So unless you have peak torque at 1k and peak power at 2500 you don’t want the curve all in by 2500.
With only that distributor?
I'm not sure which distributor your refering to but I see this with locked hei and locked msd distributors when checking timing on the engine.
Hmmmm. Maybe. If you have multiple lights and you look at the timing with all of them (thinking out loud) the slower light will least amount of timing because it has the slowest slew rate.
Is that what I said or did I say it the other way around?
It should be the slowest light will show the least amount of timing.
Hopefully that’s what I said.
If not I’ll go back and find it and edit it.
In your original post you asked him about the FAST distributor. I wasn’t sure if that was the distributor you were referring to.
I did. I suspect he is not using a fast distributor based on the amount of timing retard he saw with a fast box. I haven't heard a reply yet.
Yes, I think this is backwards.
I appreciate your comment about the curve following the VE of the combination.
The information that I posted is seems specific to a very large combustion chamber and early piston designs (mid 70's) of their application.
When the SS cars ran (low 11's) and especially the GT class cars (low 10's with 9.5:1) at 6000' + DA. I asked them how that was possible, and they said that their focus was on their LSA (very narrow) which increased VE at the top of each gear due to the design of their headers: additional "comments were made about a timing variation at the top of the RPM cycle," but the comments were somewhat ambiguous to me as I'm not well versed in their concepts.
Last edited:
TT5.9mag
Two atmospheres are better than one
I would love to have a conversation with guys that have done testing on that level.
Interesting.
Certainly DA makes a difference in how much time you can use.
As does chamber shape etc.
I’d love to hear about the variations at the top of the rpm cycle. That sounds interesting.
lol now I have to think about it. When I’m standing there doing it I know. When I type it out it comes out backwards.
Ok, I had to get on the phone. Not only is there slew rate that affects the timing light, there is when the light triggers and how much filtering there is built into the light. I forgot about that.
Generally, the non dial back lights have the least amount of filtering and they trigger on the leading edge of the spark. They also have the least amount of slew rate (generally speaking) so that light will show the least amount of timing.
A dial back light has some extra slew rate due to the electronics in them. Also, some of them also dont trigger on the first signal. Especially with multiple sparks at lower rpm, some of the dial back lights do not trigger on the first spark. I have no idea how the internal crap in the light does it, but that’s what Im told. So it may read the second or third spark at lower rpm. Which is interesting because I have used some lights that LOOK like the timing is backing up with rpm when what is happening is the light is getting just one spark when the rpm gets high enough that the ignition is sending just one spark.
The worst lights are the digital lights. They have the most electronics in them and they are slowest.
So the light with the least amount of slew rate and filtering will show the least amount of timing. Especially if it triggers on the first spark of a multiple spark ignition.
I still think that is backwards. A faster light will read a higher timing number before top dead center.
Ironmike
Well-Known Member
MSD distrib. Also, the 3 -4 degree retard I posted about was using an MSD timing light. Using my old Craftsman dial back, I got 5 degrees retard.
-
Similar threads
