Power Tuning

[FreeBeeTony]

Power Tuning..........

How can you tell if you have too much advance?
Is it only if it pings?

I am currently set at 8* BTDC but I think it may like more...........last year I had water fuel problems (at the time I was set at 10* BTDC) and I backed of the advance to 8* and lost ~200RPM. I then cured the water/fuel problem but left the timing at 8*..........figured better safe than sorry, but if I can get the 200RPM back by going back to 10* I would like to, this may alow me to turn a bigger prop and get better cruise numbers. I am currently turning a 4 blade 16" pitch........I plan on starting this season at 10* BTDC w/ a 17" 3 blade.

I read in Dennis Moore's book his method of "power tuning".........I believe he states to increase the timing in 2* increments until no further improvement is realized and then back off 2*.

My question is: will it ping at the point increasing the advance no longer provides any improvement? I would like to try this but don't want to damage anything long term by running too close to detonation.

 

[JustJason]

Re: Power Tuning

will it ping at the point increasing the advance no longer provides any improvement?

Yes... and that's how Mercruisers MBT (mean best timing) works. It advances the timing until there is spark knock, then backs it off a few degrees.

The only problem though, and this is a biggie, is that human ears cannot always hear spark knock. Even knock sensors don't always catch it. If your hitting WOT I wouldn't worry about advancing the timing any more.
If you are running a carb you can always tweak that to improve your low end and hole shot.

 

[Don S]

Re: Power Tuning

How can you tell if you have too much advance?

Either get an advance timing light or a timing degree tape you can stick on the balancer and look at the timing at different rpms. Mercruiser has pics of the advance curves in the service manual. Then all you have to do is run the engine and check it at the different rpms.

For max advance and rpm, I usually rev the engine up to max advance of the timing and let it off. Then while watching the timing mark start reving the engine till it gets to the max advance you found earlier, and look at the tach

 

[FreeBeeTony]

Re: Power Tuning

Hey Don............just trying to find out how much is too much.
I have read that for a SBC the max advance is 34-38*BTDC.
I have a 24* Thunderbolt IV module.........w/ 8* initial advance it would give me 32* max advance.
Just trying to get the most out of what I have.............

 

[Don S]

Re: Power Tuning

Have you actually checked it to see what dgrees of advance you are getting? Those modules have a range, they are NOT exact.

 

[Bondo]

Re: Power Tuning

Just trying to get the most out of what I have.............

Ayuh,.... Nothin' wrong with That,...

You can run higher timing by richening the Fuel,...
Or, from another angle,...
A sudden Lean condition can get Catastrophic Quickly running advanced timing....

Is your motor accessible in your boat, in the water, at Speed,..??
You've got an Edlebrock carb,..??

 

[FreeBeeTony]

Re: Power Tuning

No, I haven't actually measured it...........guess I should buy one of those tapes I have heard about.
What is the max a marine SBC should run at?

 

[Bondo]

Re: Power Tuning

guess I should buy one of those tapes I have heard about.

Ayuh,... I've been thinkin' of buying 1 of those Timing Lights that do that with a button....
A piece of Tape would probably be Cheaper,....

38? sounds Awlfully Hot to me.....
Might have to dig out Dennis' Book,+ see what he has to say about it....

 

[FreeBeeTony]

Re: Power Tuning

Correction.........Dennis states 30-34*...........guess my max initial timing s/b 10* w/ a 24* module..........
Do Vortec heads tolerate more timing?

 

[FreeBeeTony]

Re: Power Tuning

Ayuh,.... Nothin' wrong with That,...

You can run higher timing by richening the Fuel,...
Or, from another angle,...
A sudden Lean condition can get Catastrophic Quickly running advanced timing....

Is your motor accessible in your boat, in the water, at Speed,..??
You've got an Edlebrock carb,..??

Hey Bondo.........missed this post.

Yes the motor is accessible in the boat and I do have an Edlebrock carb.....

What are you suggesting? Didn't really want to start foolin with the carb.....was just hoping to give the distributor a twist.........

 

[Bondo]

Re: Power Tuning

Ayuh,....

Not really suggesting much of anything,...
Just pointing out that there's More to the equation than Just the timing...

Adjusting the timng while underway can give you some insight as to How much is Too much...
'course it takes somebody to drive for you,+ some reasonably Flat water...

 

[captmello]

Re: Power Tuning

Ayuh,....

Not really suggesting much of anything,...
Just pointing out that there's More to the equation than Just the timing...

Adjusting the timng while underway can give you some insight as to How much is Too much...
'course it takes somebody to drive for you,+ some reasonably Flat water...

Ya, so then what? I'm getting my 1409 in a couple weeks.

 

[bigred95stang]

Re: Power Tuning

What about running a higher octane of fuel? Say going from 85 to 87 or 89?

 

[puotha]

Re: Power Tuning

we have minimun 95 octane here in finland.what is max advance,and what rpm it must be there?

 

[wca_tim]

Re: Power Tuning

Correction.........Dennis states 30-34*...........guess my max initial timing s/b 10* w/ a 24* module..........
Do Vortec heads tolerate more timing?

typically yes by a couple of degrees... I was always told that the gains for further advances in timing really flatten out before you get to the detonation point and to just keep edging the timing up until it no longer made much of a difference, then back off a degree or two... I'm also a strong proponent of measuring timing at or above the max advance.

If you're jetting the carb at the same time... heed Bond-O's words. If you lean it out and get the timing too advanced at the same time... it won;t take long to see why it's not a good thing...

Personally, I prefer to run the jetting a little fat and the timing advanced

 

[Tail_Gunner]

Re: Power Tuning

I believe i have read enough over time to understand power tuning...Back in the day with points and vacum advance we would first tune a motor with a dwell meter then the timing light. After that was done we would place the car in drive hold the brake and stomp the accelerator. From there it was a simple as advancing the curve until she knocked or stalled. Those were the day's of Vacum Advance..

From there after two or three runs you would find the sweet spot and adjust the idle....Are your trying this type of thing with electronic ignition???..I hope not...electronic ignittion modules have different curves for different rpm levels...

If that is what your are doing i would think your flirting with diaster...today's fuel is very poor as compared to the 60--70's

 

[wca_tim]

Re: Power Tuning

today's fuel is very poor as compared to the 60--70's

and getting worse every day! as we find more ways to get more burnable fuel out of a barrel of oil - at the expense of having a broader distribution of crap in it - it winds up having everything but the kitchen sink in it.

 

[Tail_Gunner]

Re: Power Tuning

and getting worse every day! as we find more ways to get more burnable fuel out of a barrel of oil - at the expense of having a broader distribution of crap in it - it winds up having everything but the kitchen sink in it.

like lead...removal of that lubricant ruined more that one or two heads.....err valve's

 

[MikDee]

Re: Power Tuning

I believe i have read enough over time to understand power tuning...Back in the day with points and vacum advance we would first tune a motor with a dwell meter then the timing light. After that was done we would place the car in drive hold the brake and stomp the accelerator. From there it was a simple as advancing the curve until she knocked or stalled.

From there after two or three runs you would find the sweet spot and adjust the idle....Are your trying this type of thing with electronic ignition???..I hope not...electronic ignittion modules have different curves for different rpm levels...

If that is what your are doing i would think your flirting with diaster...today's fuel is very poor as compared to the 60--70's

That was my way of doing it as well back then, pinging will change, get more or less, depending on a lot of variables especially the temp, & humidity of the day,,, and usually, too much advance, and you'll have trouble cranking it to start (sounding like a dead battery). There's a lot to consider here, especially under a constant heavy load.