Timing Marks ?

[twoskies]

hello

1972 c10 with a 1979 350/4 motor

had some issues recently with running, ended up being something i changed, changed back, now it runs, seems ok

Here's the question

TDC set by holding finger over number 1 plug hole, then turning crank to 0 on timing tabs

set distributor in rotor to number 1 plug firing pretty much pointing at number 1

starts up ok,
Timing marks never show with timing light, have to set by ear

as stated, seems to run ok, but bothers me that marks dont show

any help appreciated

[truckster]

Have you tried putting white chalk or paint on the timing mark? That can make it a lot easier to see.

[Andy4639]

1979 350 timing mark on timing gear cover want be correct for the factory 72 setup either. You will need to get the correct timing marker as well. It all depends on which balancer you are using also.

[ssjody]

There could be several reasons for this.
1. The outer ring of a bad balancer can actually slip. You could mark a line on the outer ring and main hub of the balancer and see if that outer ring is moving.
2. Do you have an adjustable timing light? If so Is it on zero?
3. Did you have the vacuum advance hooked up when checking?
4. What RPM's are you running at idle? if it's high could have some Centrifugal advance coming in.

A good way to find true TDC is with a piston stop. If you are not familiar with what that is you can google it where you'll find plenty of info on the device. They're simple but they work. Once you know where true TDC is on your balancer you have a good starting point to figure out your problem.

[Oldironside]

Once I had the same issue. Turned out I had a vacuum leak at the foot of the carburetor.
Fixed the leak and the timing marks appeared again
Of course it could be something else but making sure there is no leak is an easy task and you can either locate the problem or eliminate it as the cause.

[twoskies]

Thank's for the replie's

balancer marked with a white marker
vacuum advance unhooked
still no marks

Andy, Thank's for the diagram, the motor is a 1979, but its always been able to setup and see the marks before

only thing im thinking now is, bought a new accel distributor , came with an adjustable vac advance, followed directions to the letter but guess could be off

[LS short box]

Best way is using a piston stop as said above. Easy to make one out of a old spark plug. Knock the center electrode out of the plug and weld a short piece of metal to the end of the plug. Take all the plugs out and screw the newly made piston stop into the number one hole. With all the all the plugs out take a wrench and slowly turn the engine over until the piston contacts the piston stop. Now mark the balancer next to the timing tab. Now turn the engine the opposite direction until it contacts the piston stop and mark the balancer. Half way between those two marks will be TDC.