Total advance timing

[Harbernjero]

Hello,

what experience do you have in total advance timing.

I found this in Fordmuscle-Magazin:

http://www.fordmuscle.com/archives/2000/03/timing/index.shtml

The rule of thumb is that the higher the compression ratio, the less total timing it can handle before detonation, and also the higher octane rating it needs to control detonation. Low octane fuels ignite faster, thus require less timing advance. Conversely high octane fuel can handle slightly more advance. Dyno testing has shown that most small block Fords with 9:1 to 9.5:1 compression make peak HP with 38-42 degrees total advance. Engines with 9.5:1 - 10.5:1 run best with 35-38 degrees total, and above 11:1, should not go higher than 35 deg. total.

:idea:

Thanks Claus

 

[c9zx]

Like most questions, the answer to how much advance to use is "it depends". Assuming the engine components are well matched, much depends on the effectiveness of the combustion chamber design. The better the design the less total timing is required to build maximum power. I've seen max occur with 28 degrees using the old Ford Racing 351N heads and 40 degrees with factory 302 heads. the only accurate ways to answer the question is several dyno pulls or several drag strip passes (if the mph goes up it is making more power). My 408C made best power with 34 degrees and best torque at 36 degrees. I have more torque than is needed so timing is set at 34 total. A 330 cid small block Ford with AFR 185 heads made best power at 32 degrees total. Determining initial timing on a significantly modified engine is a different, more complex exercise. Chuck

 

[Harbernjero]

Hi Chuck,

the motor produce a dynamic compression ratio 9,3:1 with the Edelbrock Performer Plus 204/214.The Accel Distributor is set to provide 22° of advance and I add 14° initial,so i get 36° total.I run Procomp Aluminum Heads with 60cc D-Camber and Keith Black forged pistons.

500 cfm carb.

The performance ist good but i thing it gets better with more timing advance.

I know i have to pay attention because of pinging.

I`ll try next year because now is wintertime here in Germany.

Thanks Claus

 

[c9zx]

Good luck with your tuning in the spring. Chuck

 

[MeZapU]

Compression in regards to total timing is more a factor of total volume of air/fuel to be burned, added to the efficiency of the combustion chamber design.

The 408 in my 85 GT likes 32deg total with 10:1 and AFR 185 heads. Any more timing and it loses power on the dyno.

 

[Harbernjero]

Very interesting what a difference with a little change in motor build up or size.

 

[Harbernjero]

Now i`am a little confused.

I got an ACCEL Distributor Series 52000.

The Installation Instruction says:

Mechanical Advance

The ACCEL 52000 distributors are factory set to provide

approximately 20° degree (crank) of mechanical advance, starting

at about 900 RPM all in by about 2100 RPM. This is a good

general-purpose curve and will work for most applications.

Next chapter they say:

Selecting and Changing the Advance Stop Bushing

There are three different advance stop bushings are supplied in a

kit with the ACCEL 52000 distributor. No stop bushings are

factory installed which yields approximately 22° degrees of

advance.

http://www.jegs.com/InstallationInstructions/100/110/110-52201.pdf

Is it now 20° degrees or 22° ? :huh:

Can anybody help me understand this?

Thanks Claus

 

[MeZapU]

Just try it and see what you get. Two degrees wont hurt you. Start with 12 deg initial + 20 deg of mechanical advance = 32 deg total.

 

[PAPPY HAROLD]

This is often a confusing area. I'm no expert but have played with a few. There are factors involed that I havent seen mentioned, Carburation induction and camshaft all come to mind, Head air flow and compression are right there as previously mentioned. M y experience with accell is none but the basic operation is pretty much common. Different combo's of springs change how much advance you get at different rpm's and the bushings control how much total advance its allowed to give. Take a look at the charts I'm adding and see if it helps. but as the guys said its try and see to find the right combo, if you dont have the dyno then its use a combo run it ,see if its better or worse, try another and compare.

http://www.msdignition.com/page.aspx?id=12884901958

 

[Harbernjero]

OK guys,thanks for answer.

I share the same opinion.I have to try and see what happens.

I´ve got one more question:

When the motor start knocking by detonations cause of to much advance timing - is it hearable?

And ist it hearable at 3000 rpm,because of side noise ?

 

[c9zx]

OK guys,thanks for answer.

I share the same opinion.I have to try and see what happens.

I´ve got one more question:

When the motor start knocking by detonations cause of to much advance timing - is it hearable?

And ist it hearable at 3000 rpm,because of side noise ?

This is the best article I've read on the subject. http://www.streetrodstuff.com/Articles/Engine/Detonation/index.php

With mufflers you'd probably hear it at 3000 RPM cruise. At wide open throttle at 6000 RPM probably not. If it goes on long enough, without pre-ignition, the rod bearings are damaged and you can't understand why. Chuck

 

[will e]

OK guys,thanks for answer.

I share the same opinion.I have to try and see what happens.

I´ve got one more question:

When the motor start knocking by detonations cause of to much advance timing - is it hearable?

And ist it hearable at 3000 rpm,because of side noise ?

Yes, you will hear it. My car is pretty loud but I can hear the ping.

 

[Harbernjero]

Hi guy`s,

thanks for this great article.::thumb::

And it`s good to know that the ping is hearable.:goodone:

Can`t wait for springtime.

Claus