GM distributors I'm familiar with have a 5/32" hex socked head on the side
of the points. If you do have that then the .022" feeler gage is good for a
start. When you get your timing worked out and it will start and run,
insert the allen wrench through the window in the distributor cap to the
socket on the points and rotate clockwise util it starts to run rough. Then
rotate cc until it runs rough. Finally, go back to the mid point between
the two positions and you'll be in good shape. I've used that method on a
1970 Blazer with a 350 for all the years I've owned it (since 1978).
LD

wrote in message
ups.com...
Newly rebuilt GM 153ci, mercruiser, 120hp, 1987 model. Backfiring
through carb. I suspect that I've gotten the spark timing off some
how. I have the manual and I have the firing order in the correct
order, but I'm still getting the backfiring through the carb. When
assembling the engine I double checked that when the slot on the pulley
was @ 0 the #1 piston was at TDC and installed the distibutor with the
rotor button pointing toward the #1 plug wire. The engine doesn't
start. I put new plugs, wires, dist. cap, and POINTS. I don't have
any experience with points. What I did was, put the .022" feeler gauge
between the gap while the point was at the open position and adjusted
accordingly.



So my question to anyone is: How can I verify 100% that my timing is
at least close enough to fire the engine?

How do you adjust points?

Thanks