Timing mark miss placed on GMC 350?

Question

bought crated 1978 GMC 350 4 bolt main, carbs , no egr and with hei ignition. Installed dorman 002 damper as instructed by engine manufacturer with old timing cover as instructed, with pointer somewhere around 2 o'clock. This motor will not run unless timing mark flashes around 12 o'clock! Vacuum advance appears to work but hard to see how much as water pump in way. Engine starts real good and seems to run ok but it's in a motor home and very important to get it right.Anybody ever had this happen? No help from engine manufacturer or local dealers as they don't work on oldies like this!

Answer 1

On several accasions

There were several different timing mark locations used by GM . I have found four differint tab locations used by G.M, and at least six on the balancers

For some reason (unexplained)( I believe to reduce inventory numbers) they decided to use one balancer as the common replacement and don't warn the installers very well to check the timing and make the corrected location marks or tabs.The parts people have this noted to check this with the new engines and new balancers.