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Timing and max RPMs for a 360?

I think that you, myself, and a hand full of other members would also like to know what Chrysler Marine (key word "Marine") offers for ignition timing specs and WOT RPM suggestions.
We've been poking at ideas for several months now, and are still coming up empty handed.

We can find base advance specs all day long, but nothing above that!


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Jeff, I know that you know your stuff, and I am not doubting you...., but you are more brave than I am.
I won't quote numbers like this, unless I can back it up with an OEM reference.

I think that I'm OK with the 26* full in by 2,800 ........, but that 2,500 is killing me! :D :D :D


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Last edited:
Jfreeman1412 said:
When you guys talk degrees...does it include the base or is the base additional?
Click to expand...

It's tough for me to explain without going back and forth from BASE to Progressive and back again, but I'll take a stab at it. Perhaps one of the other guys can explain it better.
This will be very elementary... no offense.


Ignition Advance:
Iignition advance relates the igntion spark event to the engine crankshaft angle..........., or perhaps better said, where the piston is in it's travel. (spark occurs before top dead center.... hence the term "advance")
The advance numbers will typically include both BASE and Progressive, or it will otherwise be stated.... or should be stated!


BASE or Initial Advance:
(sometimes the word "initial" works better)
BASE or Initial advance is simply a function of where the distributor housing is positioned and locked down, and is always prior to any distributor advance (mechanical or EST).
This amount of advance will remain in BASE or Initial range until approximately 900 to 1,000 RPM and later. Only then will the progressive advance occur.
Progressive will always be on top of, or will be additional to, BASE.

** see below


Distributor Advance:
Distributor advance (progressive and TA) is accomplished either by the mechanical system (flyweights and return springs), or by EST (electronic spark timing), of which is done via the ignition module for these EST systems.
However, when we view ignition advance via a timing light, the numbers that are seen can't help but include BASE.
So when strobing your timing marks, BASE is always part of what you will see.
IOW, these two cannot be separated once the engine is running and out of BASE range and into the Progressive range up to the TA.

Advance Curves:
When we view a typical Marine ignition advance curve in graph form......, the graph will show both Distributor Advance (vertical scale), and engine RPM (horizontal scale).
The graph allows us to see the progressive distributor spark lead (advance) at a given RPM.
BASE will usually be omitted from the vertical scale, so if you were to do the math, BASE must be added in order to check what the actual Crankshaft Angle total advance should be according to the curve.


TA (total advance):
TA is the full amount of advance (both BASE and Progressive) that the engine will see.
TA must always be associated with an RPM, or it is meaningless to us.
Examples of TA: 26* @ 3,200 RPM..... or 26* @ 1,500 RPM (wrong example).
Obviously the second number will cause engine damage.

Again, TA this is the sum of BASE advance and the progressive advance at it's limit!
These two cannot be separated once the engine is running and out of BASE range and into the Progressive range up to the TA.


**BASE is also the variable portion of the equation.
What ever changes we make to BASE, is an identical change to the Progressive and TA.... be it advanced, or be it retarded.
If we were to change BASE from 5* to 10*, we will have changed the TA by 5* further advanced.
The only way to change this relationship, is a modification to the flyweight system, or a modification or change to the EST controller.

NOTE: if a small change to BASE becomes necessary in order to achieve the correct TA, it's not a deal breaker...., as long as the new BASE allows the engine to fire up and idle correctly.


Once you begin strobing your timing marks, and watch as RPM increase, it will make more sense to you.
Play with it, change it, see what it does, but when finished, make darn sure it is within OEM specs.... and especially at the TA.
A slightly off BASE or Initial advance, or a slow progressive advance will usually not harm an engine.
Advance too early, or excessive TA, certainly will.




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Last edited:
It would be nice if you gave credit to original author of this copy&paste. :)

Ignition Advance:
Iignition advance relates the igntion spark event to the engine crankshaft angle..........., or perhaps better said, where the piston is in it's travel. (spark occurs before top dead center.... hence the term "advance")
The advance numbers will typically include both BASE and Progressive, or it will otherwise be stated.... or should be stated!


BASE or Initial Advance:
(sometimes the word "initial" works better)
BASE or Initial advance is simply a function of where the distributor housing is positioned and locked down, and is always prior to any distributor advance (mechanical or EST).
This amount of advance will remain in BASE or Initial range until approximately 900 to 1,000 RPM and later. Only then will the progressive advance occur.
Progressive will always be on top of, or will be additional to, BASE.

** see below


Distributor Advance:
Distributor advance (progressive and TA) is accomplished either by the mechanical system (flyweights and return springs), or by EST (electronic spark timing), of which is done via the ignition module for these EST systems.
However, when we view ignition advance via a timing light, the numbers that are seen can't help but include BASE.
So when strobing your timing marks, BASE is always part of what you will see.
IOW, these two cannot be separated once the engine is running and out of BASE range and into the Progressive range up to the TA.

Advance Curves:
When we view a typical Marine ignition advance curve in graph form......, the graph will show both Distributor Advance (vertical scale), and engine RPM (horizontal scale).
The graph allows us to see the progressive distributor spark lead (advance) at a given RPM.
BASE will usually be omitted from the vertical scale, so if you were to do the math, BASE must be added in order to check what the actual Crankshaft Angle total advance should be according to the curve.


TA (total advance):
TA is the full amount of advance (both BASE and Progressive) that the engine will see.
TA must always be associated with an RPM, or it is meaningless to us.
Examples of TA: 26* @ 3,200 RPM..... or 26* @ 1,500 RPM (wrong example).
Obviously the second number will cause engine damage.

Again, TA this is the sum of BASE advance and the progressive advance at it's limit!
These two cannot be separated once the engine is running and out of BASE range and into the Progressive range up to the TA.


**BASE is also the variable portion of the equation.
What ever changes we make to BASE, is an identical change to the Progressive and TA.... be it advanced, or be it retarded.
If we were to change BASE from 5* to 10*, we will have changed the TA by 5* further advanced.
The only way to change this relationship, is a modification to the flyweight system, or a modification or change to the EST controller.

NOTE: if a small change to BASE becomes necessary in order to achieve the correct TA, it's not a deal breaker...., as long as the new BASE allows the engine to fire up and idle correctly.
Click to expand...
 
Sea Clam said:
It would be nice if you gave credit to original author of this copy&paste. :)
Click to expand...

I'll take that as a compliment in that you must have thought it was well written. Thank you!
I'm sure that I could have done better given more time!

And you are correct, it is a copy/paste from my word processor that I used when I typed it out.

Some people do plagiarize, and you can easily catch it by searching one paragraph word-for-word at a time.
If it's been plagiarized, it will usually come up.


Sea Clam, if you have anything to contribute to this topic, please do!
More info, OEM specs, corrections, suggestions, etc.





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Last edited:
greasemonkey said:
I think I know who's not:p in the "Circle of Trust"
Click to expand...
:D

pete31 said:
wonder if he gave credit to the artist
Click to expand...

I'm thinking that the artist does not yet drive a car, nor do his own laundry. :D

avatar61616_1.gif



Although I must say, it's better than some of my MS Paint marked-up drawings!

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