Timing drives me crazy.....

[brasil]

 Good morning America....

A german car mechanic is close to be getting crazy....  Why ?  Because of the Ignition timing ...  My engine is a 340 cui with x heads TQ carb ( AFR Numbers are  13 @ idle....   14.5 while crusing   up to  11-11.4  under WOT / heavy acceleration )  so the carb is not involved..I think.
Vacuum @ idle in Neutral is 12 inches of mercury..  ( Stable )   I use the best fuel avalible in Germany..ARAL 102  octane...  should be your Premium pump gas....

The timing is  16 deg @ idle...and 18 deg. advance   ..so 34 deg all in   Vacuum advance  around 13 deg on top.  the curve starts at 1000 upm  which is 150 upm above idle  upm... the curve ends around 2800 rpm.....   I need the 16 deg ( or even more ) at idle to get a good idle..if I go down to 12 deg or so...the trottleblade of the carb has to be opend until the screw comes to the very end.... 

And here comes the problem :   PINGING   under acceleration....   more under  Part Trottle than under WOT....

So I pluged the vacuum canister...  ( made no difference... )  then I reduced the timiing @ idle ...down to 13 deg....    now the ping is less....  ( but I hooked up the vacuum again )....   later I will run again with the vacuum pluged..   if it is still pinging.....  what can I do ?

Lowering the timing @ idle  will have bad effects to the idle... high numbers @ idle are fine for the idle...and vacuum .. but then  I am afraid to be back in the pinging area...

I have the Accel OE replacement Distributor...so I can adjust the advance from 0  to 28 deg. in steps of 2 deg. ....


Thank you for good ideas....

Greetings from Germany
Juergen

[734406pk]

 I would suggest leave your base timing at 16 deg BTDC, reduce the centrifugal timing to 14 degrees and leave the vacuum advance disconnected and plugged for now. Take the car for a test drive and see if there is a change. 

[Chryco Psycho]

use a heavier spring on the mechanical weights so it advances slower

[Bullitt-]

Are you positive the timing mark on the harmonic balancer is accurate?
I've heard the outer ring can slip... 

[bandt]

I would suggest leave your base timing at 16 deg BTDC, reduce the centrifugal timing to 14 degrees and leave the vacuum advance disconnected and plugged for now. Take the car for a test drive and see if there is a change. 

I agree. Reduce your mech. Advance. Leave initial at 16*

[HP_Cuda]

What is your compression ratio, if it's too high your 102 octane is not enough and will ping.

Yes playing with the timing will help but in the long run you may have to run higher octane or add more boosters.

[CUDA JAS]

use a heavier spring on the mechanical weights so it advances slower

 

I am with CP on this one.

Jason

[Strawdawg]

Make it three...heavier spring.  Look for full advance around 3600 in this case.

Go up a couple of jet sizes as well

[RCCDrew]

Are you positive the timing mark on the harmonic balancer is accurate?
I've heard the outer ring can slip...

[Oldschool]

Confirm the octane of the fuel you are using. It might not be as high as you think...   

[brasil]

WOW 

so many answers ..Thank you guys.

I was also busy today....   and I think..I found the reason....   Chryco Psycho   was damn close....     

Here is the result of my todays  research...   The Distrtibutor has 4 perches...where you can hook up the springs...  normaly we use a heavier  and a lighter
spring....   so far so good..  The only thing was that the distance between the perches  was to close....   so the bigger spring ( with the light sloop ) had no function at all...   only the lighter spring was involved but of course what happend ...that the advance run out of the normal curve....resulting in this awful pinging.
So I bent the perch where the heavier spring sits  a little  ....now the heavier spring acts  like she should !! 

Interesting btw...    the Distributor never worked right...because of this "little " detail !  And I bought him new ...some month ago....


Greetings Juergen

P.S   the fuel has 102 Octane...but here in Germany we calculate the Octane value  different from the US
       

[73_Cuda_4_Me]

Hmmmm.... that spring setup sounds EXACTLY like my factory stock spring setup...   

The heavier spring comes in around 2,500 RPM (because of the 'loop' slack at one end), and changes rate of advance from that point up to full RPM...

I think you would be better off using a 2nd lighter (non-loop) spring, rather than bending post so heavy spring is always resisting... I suspect you are pushing advance curve start close to or above 2,000 RPM, and all in up around 3500-4000 (DO NOT ASK ME HOW I KNOW THIS...) 

[734406pk]

  Glad you found it!

[brasil]

@ 73cuda4me...

I think that the current set up  makes sence..  because the  brown spring starts at 1000 upm  goes up to 2000 rpm and gives  around 14 deg of advance..
then the silver spring ( with the loop )  flattens the curve....  and permits another 6 deg ...  - o.k. perhaps the last 6 deg come in late.. I have to verify this..

If I use a lighter spring than the brown one..( orange for example )  the curve is faster.... but the  orange spring comes in @ 750-800 rpm...to soon..  because my idle is around 900 upm... 

In the instuction sheet from the mopar "trick kit "   they say... stay with one HEAVY spring ( i.e  with the loop )   because using 2 light springs create a strait line...not a curve...   and my car is a street driven car..   ( or better should be one.. )

Greetings Juergen

[Chryco Psycho]