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
