Hey Jim,

I'm not sure that there are any smog rules for a vehicle this old. I bought it 
in Ca, and they required smog for 73 up. Here in Tx it's 78 up. So no I don't 
need to be concerned about it.

The distributor is an 003.

Setting up the 8 BTDC would that be at 800 rpm?

What about when I attach the advance, do I need to bring that down to 800 rpm 
as well?

Thanks

George
-------------- Original message -------------- 

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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