I have just finished a GM long block swap into my 1997 GMC Jimmy. I used the EDI Engine Timing link to set up the distributor correctly and it fired right up. I used a Tech2 to read the CMP Retard as described and it was at -11degrees. I was only able to get the value down to -7degrees. I have test drove the vehicle and I can't tell that the CMP Retard being off by 5 degrees has caused a performance issue. It starts right up and idles well. I have only be doing "normal" driving without any hard accelerations as the engine installation instructions mention no hard accelerations for the first 500 miles. My question is will having the CMP Retard set at -7degrees instead of the stated 0 plus or minus 2 degrees have any long term effects on the vehicle? Will it cause more problems down the road for me?

One other question, I am sure it might be a stupid one, but I am still learning, so there can't be a stupid question right? How does just sliding the distributor side to side in the slot change the retard value? It seems like to me it should be more of a rotation and not a translation. Obvisiously, it works, I just don't understand how it does. Can anyone enlighten me?

 

I doubt that having a CMP Retard of -7 would have any harmful effects. When its way off, premature wear on the drive gear is a typical sign.

As far as how it works, by shifting the distributor body in the bore, you are altering the angle, just not as dramatic of a change as when you could manually turn the distributor body.