In a message dated 8/18/2005 4:45:14 A.M. US Mountain Standard Time,  
[EMAIL PROTECTED] writes:

Thanks Russ,
 
Do you know what the timing should be set for that situation? On my 250  it 
states 4 ATDC but that's with the system  retarding.



George,
 
We should establish what kind of smog test you will have to pass before you  
bypass the factory stuff.  If no restriction, I too, would go for a  straight 
advance scheme, keeping in mind you have both vacuum and centrifugal  advance 
to deal with.  
 
I would think 8 degrees BTDC would be a good starting point, depending on  
the quality of the fuel you use.  This with the vacuum line disconnected  (and 
plugged) and the idle speed low enough so that you see no fluctuations in  
timing as the engine idles.   Then make sure your damper is marked in  degrees 
up 
to about 50 BTDC so you can rev the engine and check TOTAL advance,  which 
should be in the ranged of 32 to 36 degrees.  This with the vacuum  advance 
disconnected.   
 
 Keep in mind, I do not know the specs of your distributor so I am  guessing 
it has about 24 degrees of centrifugal advance and maybe 14 degrees  
additional vacuum advance.  Depending on the average climate and the fuel  
quality, you 
could be  right on the edge of pinging some of the  time.  A little light 
pinging at part throttle is acceptable.  NO  pinging should be heard at wide 
open 
throttle under load or engine damage will  occur!  With WOT,  vacuum should 
be approaching zero and no vacuum  advance should exist.  
 
Now we connect the vacuum advance to a port showing vacuum ALL the  time.  
This will give you much better low speed throttle response, as well  as the 
best 
part throttle mileage.  Revving the engine to a point of all  the centrifugal 
advance being in plus a strong vacuum signal should show a total  advance 
somewhere around 45 degrees BTDC.  
 
With a light throttle,  driving down the road, this much advance will  be OK  
as the lean mixture must be lit off quite aways in advance to  produce power. 
 If a lot of pinging is heard, some way of limiting the  vacuum advance may 
be  prudent.  Us Chevy guys merely put a sheet  metal screw in the slot of the 
timing plate inside the distributor, thereby  stopping the travel of the plate 
due to vacuum.
 
Hard starting usually means too much initial advance.  If you start at  8 
degrees BTDC, you should not have  a problem.  Add timing in 2  degree 
increments 
to find the best setting that provides the most power without  full throttle 
pinging, and acceptable starting qualities.  
 
Have fun,  

Jim  Friesen
Phoenix AZ
79 300SD, 261 K miles 
98 ML 320, 137 K  miles

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