Originally Posted by marshal135

May I offer a recent experience I had with my '68 427/390hp points distributor:

I went through this last winter too.
I forgot to mark the distributor housing and manifold relationship before pulling.
I replaced the tach cable and reinstalled the dist.
It backfired something fierce out the carb.
I had to start from scratch.
A little back ground:
First, the distributor housing has to be clocked in the proper position.
When they went to a cable driven tach dist they realized they had the drive gear
orientation off. Hence early cable failures.
GM put out a service bulletin to their dealers mid 1968 regarding




re-clocking the dist housing. Alan has referenced this in another thread.
Hence, the firing order remains the same but the plug wires at the cap were moved counter clockwise to the next position.
So in order to get the dist shielding on correctly later, the vac advance can
should be pointed at the passenger front fender or the 2:00 position if seated inside the car.
This allows turning room for the dist as the shielding bracket limits travel if not set right
and not to mention an ugly bend on the tach cable.
After this is oriented you need to align the rotor towards the number 1 cylinder.
This is the first plug on the driver side just under the alternator or 11:00

















position again if seated inside the vehicle.
The vehicle's engine must be brought up to TDC in cylinder #1 before dropping the distributor back in. Take a glance at the timing scale and pointer on the lower balancer.
They need to be lined or your 180* off. If need be white grease pencil or white out works fine to mark reference points. You'll need this later on for timing.


If these are lined up, finesse the distributor into the block until the bladed end drops into the respective slot internally. This slot can be turned with a wide flat blade screw driver to keep the dist oriented properly.
It's a feel thing it will drop in with patience.
Tighten the hold down bolt down just enough to prevent movement on restart but loose enough to turn by hand with a little effort.
Reinstall plug #1 and wire.
Important before reinstalling the dist cap..... make sure wire to plug #1 is over the rotor
while aligned with cylinder #1.
Set the cap in place to orient the rotor and appropriate tower. If need be place a white dot on the side of this tower to maintain proper orientation.
Now get out the manual and check firing order and verify each plug wire is oriented correctly in its firing order. The Intake manifold should have the cylinder numbers cast above each cylinder.
Check to be sure each plug wire is routed to the correct plug. 1 off and it
runs rough.

Fasten the cap down.
Attempt to start. It should at least run at this juncture.
Plug the vac advance can line on dist and time as required per Lars paper.
Check for recent version as fuels have changed for the worse and timing is no longer
all in cruise at 52-54* anymore unless your running hi octane fuels. Pumps are supporting 34* with 10-12* advance added from vac advance.

Anything else leads to pre detonation or the death rattle.
It sounds like there's marbles bouncing around in the valve train.
Not good to leave in this condition, timing needs to be retarded.
I know I threw a lot at you but not sure how familiar you were with the procedure.
It was previously explained to me that's how I learned.
Please let us know how you make out.

Definitely email Lars as directed in above post.
Read his timing papers several times as it sinks in a little better each time you re read it.
Marshal

Originally Posted by Chapter2

If you want to find the exact position of cylinder #1 TDC at compression stroke, then forget about the marks on the harmonic balancer, the outer ring may have slipped after all these years, which will throw off all your readings. Instead, use a piston stop. You can look up how to make and use one. Pretty easy, and much more accurate than the harmonic balancer/timing marker.

Originally Posted by Bhebert449

Originally Posted by Bhebert449