Oh no...... I'm allowing myself to get sucked in once again.
Dam it......., I'm one hard headed guy, aren't I?
For you "Nah Sayers"......... are any of you guys familiar with marine load detonation, and what the damage looks like if it were to occur?
If not, take a quick look here.
These aren't all Marine pistons, and they aren't all from the same degree of detonation, but it should give us a good example of what to expect should our ignition timing Total Advance be too great and too early!
The catch is often "just how close are we to detonation"?
Are we receiving enough TA for performance, or are we leaving horse power on the table?
(often the OEM specs are very conservative)
Are we so close that given the right load, poor fuel quality, the right atmospheric conditions, over-propped, etc, that we risk detonation?
The only way to be safe, is to use the OEM specs for the particular Marine engine, and make sure that the distributor (or EST system) is giving us this.
The engineers have spent countless hours researching this.
Setting BASE only tells us ZERO of what TA is, unless we take it further by actually checking it dynamically, and at the RPM at which it is to be "Full In".
Dan, Oldhat,
If you set initial @ 5-7° BTDC with a light on the flywheel at idle, if you have not already, check to see if another mark shows up @ 2200 - 3000 rpm. Maybe the flywheel has a mark already on it for total. Worth a shot?
Excellent point!
Keep in mind that Marine Engine ignition induced detonation can begin as early as 2k rpm and up.
This why the Igntion advance is "Progressive", and for the most part,
linear.
I actually have checked the total advance on my boat with an adjustable timing light but I have never heard of another marine mechanic or owner ever doing that.
I too have spoken with (and heard of) the so called "Marine Mechanics" that never look past BASE advance.
I think that these guys are doing a disservice to their customers.
That's like checking the air pressure on one tire, and then kicking that tire........., and then going around to the other three tires, and giving them a kick ONLY!
I have all the original manuals and nowhere does it say what it's supposed to be.
I think mine is 25-28 degrees.
The 25-28 degrees is great to know if these are correct for your Marine engine......, but without an associated RPM, the numbers are meaningless.
Is it 28* @ 2k rpm?
Or is it 28* @ 3k rpm?
Under Marine Engine loads, 28* @ 2k rpm is a recipe for detonation......, IMO.
I have had a race car for 40 years and know how to set them up,
Then you know full well about LPCP or PCP, and what this means.
It becomes of more importance for the Marine gasser.
We'll find recommendations for PCP at/near 12-14* ATDC for many piston engines, including diesel engines.
Doesn't matter what the bore/stroke is..... crankshaft angle is crankshaft angle.
For the gasser, ignition timing plays a very large role in this.
Being a race car enthusiast, you certainly know this.
While under Marine loads, a PCP of 10* ATDC may cause some real issues... or be very close to it!
my family used to have a 1948 40' Chris and the procedure for timing it was to turn it until it pinged under full throttle and then back it off a little.
So now looking a stock 440 I say just set it where it's supposed to be and go boating. Thats exactly what all the mobil marine mechanics do when tuning my dock neighbors boats. My yacht club docks are full of old gas powered boats including Lincolns, Hemis, 4 boats with 427s, several 440s and a bunch of 454s and most are original engines that get tuned up once a year by checking the base timing.
Pre-Ignition and Detonation are two entirely different phenomenon.
People often confuse the two.
To set the ignition timing a Marine engine
by listening for a "ping" is simply incomplete and irresponsible.... but this is my opinion only!
No offense to any of us..... just say'n!
As we've seen here, the 440 TA specs seem to be rather illusive..... and I wish that someone could find them.
Once found, I say follow them...... but make darn sure this is more than just BASE.
.