Since I know I can tune a 292/292/108 cammed 360 with a manual trans, to idle all day at 5* advance, and it will pull itself at 4>5 mph, with no help from the gas pedal; ....... Since I know that, I see no good reason to try to run big IDLE-advance numbers.
end paragraph
To be clear
And to no one in particular
RExcept to OP
I didn't say that I ran my hotrod at 5* of Idle-Timing.
What I said was;
" I can tune ......... to idle all day at 5* advance, and it will pull itself at 4>5 mph, with no help from the gas pedal"
and the point was?
"Since I know that, I see no good reason to try to run big IDLE-advance numbers."
END OF PARAGRAPH
Not once did I preach to run 5*. Nor eve that I typically ran my 292 equipped HO 367 at 5* advance. It was a statement of personal knowledge, attesting to what can be done when the Transfer-slot to mixture screw adjustment, is well-ballanced.
This knowledge was necessary because so many of the Forum members come forward and either recommend and/or even DEMAND, ridiculously large amounts of Idle-timing, because, I suppose, those who do so, do not know how to properly set up a distributor.......... would be my guess.
Butum, Hey, I went thru that phase also. But with a manual trans, I soon learned the fallacy of that thinking.
>> A manual trans street-car, with a big cam, IMO, should have a two-step timing curve, with the step placed somewhere between 2200 and 2800, depending on the combo; the weeaker the starter gear, the closer to 2800. the deeper the starter gear, the earlier it can come in.
The Power-timing amount depends on chamber efficiency; and,
when it can be all-in will depend on the chamber/fuel combo's ability to resist detonation. When you find that number, that is your semi-permanent target and all other mods to the distributor, have to end right there.
I get it.
So with a short straight race-car timing curve that everyone is so hell-bent on running, you gotta start high to get there. But a street-car is not a race car. A race car cares about timing just once, namely WOT;, But a street-car spends most of it's life between stall and say 3500, the zone where timing is much more important; get it wrong and you end up with an engine somewhere between being detonating pos that requires best gas, or is a stinking lazy dog with bad manners.
>>The only change that I see relevant, when applying this knowledge to an auto equipped street-car, is when the switch happens, which can be at or near stall.
The thing is, a street-car manual trans or not, also spends a significant amount of time, cruising at some steady rpms both above and below the stall, where it's gonna need close to or more than double the amount of timing, that the Power-Timing curve can supply. So then, you are gonna have to marry the Vcan timing to the Power-timing, in order to get some decent mpgs, cool running, and a civilized personality. This almost invariably means modding the can to max the timing at 22>24 degrees. aaaaaand when you add that to the power-timing at a stall of say 2200, on a straight timing curve that begins at 18*@1000rpm, pow! you are likely to get detonation everytime you roll into the throttle.
On a straight curve that begins at 18*@1000, and ends at 36*@3000,
that is 18* over 2000rpm,
which is 9/10th degree per 100 rpm.
Therefore, at a 2200 stall, the curve will bring 10.8* to the 18*, thus a total of ~29*, Whereas, the engine might be wanting 51* for best fuel economy.
Which is 51 less 29= 22* in the can. which could/might be fine ........ until you speed up. At 2600 the Power-timing with this straight curve will bring an additional 3.6degrees to an engine that is not wanting it and may in fact be wanting less than 51! So maybe it goes into a low-level detonation, mile after mile after mile. <I SAID MAYBE>
You don't notice the loss of power, cuz the throttle is so little open....... until you need to gas up and you see that your mpgs took a dump, related to the somewhat larger than necessary throttle opening. The way I caught that, was with a dash-mounted vacuum gauge and a dash-mounted timing retard box.
So the result of all that, was a new
two-stage timing curve, and marrying the vcan to the new curve, at the highest rpm that I was likely to cruise at, and living with the the timing shortfall at lower rpm cruising.
For a stick-car, with an overdrive, this has other advantages, namely, I have lemmee see, oh yeah FIVE different cruising speeds all at the same rpm, just in different gears.
In my combo for instance; 2240 rpm is; mph of
16/26/36/51/65 in overdrive. Whereas, Speed limits up here are;
..........35/50/62/68 on the TransCanada Hiway.
So as you can see, I always have a peak efficiency cruiser gear. aaaaaand cruising is IDK some 90 percent of my day to day driving.
So what do I care if my PowerTiming is short 2 or 3 degrees, my hi-pressure 360 already has a preponderance of torque and power, and the only time I could use more with 3.55 gears, if the tires ever quit spinning, is at 60 mph= 5100 in Second gear; which is an easy pull with an overall torque-multiplication ratio of 6.82
To me, having the Cruise-timing set up exactly right, means I can blow some cash on gas for when I actually slam my foot down.
Streeters, IMO, need to think NOT AT ALL ABOUT quarter mile stuff, and concentrate on how they actually operate their vehicles. When I finally caved in to that, is when my car finally started being fun.
Listen, I tried to set up my car for dual purpose, and can attest that set up like that, it cannot do both with with any degree of satisfaction. Not as a quarter-miler at least. Unless maybe you got a chitload more money that most of us do.
The first thing I ditched was the 292 cam.
The second thing I did was get an overdriveA833.
The Third thing I did was install a GVod behind that, which when used as a splitter, got me a solid seven close-ratio gears.
But I found out real quick that Seven gears on the street was TWO TOO MANY, even with 4.88/4.30 gears. so
The Fourth thing I did was ditch the A833od box, and swapped in a Commando Deep-Low box still with the GVod behind it. And
Then, I went back to 3.55 gears, which with the 3.09 low gear, is plenty enough starter gear.
The one common thread among my engine iterations was keeping the cylinder pressure always nearly the same. and yes, I really did deck the block three times in five years.
BTW
Idling around the parking lot with a starter gear of 10.97, at 5* advance produces rpm of 550, and speed of 4.0 mph. If a cooling system has trouble with that, it needs to re-engineered. That was with the 292 cam.
My current cam is 18* smaller at 050, and will perform the same trick at 500rpm ............ which maths to ~3.7mph. If I need to drive slower, I retard the timing some more with my dash-mounted timing-retard box; the T-slot sync does not change.
You wanna experience something cool? Driving up the ramp at the local Hamburger Joint, which would stall the engine at 5* advance, I just reach over and start cranking in more advance, as she chugs up the hill, lol.
You gotta get one of those, not for just a tuning tool, but also for the fun of playing with it. My combo actually likes up to 60 degrees of cruise-timing under certain circumstances. This number cannot easily be reached with the standard Mopar-type distributor. One would have to cruise at the lowest cruise rpm that will get you max Power-Timing of say 36*, and get 24* out out of your Vcan, and still be able to generate enough vacuum to pull it all in. .................. and then, you still gotta be able to drive it at other rpms and load settings .............................
