I am trying to set the timing on my 4.9 (84). I have noticed that there are three marks. Are they BTDC, TDC & ATDC?

 

I have never messed with a 6 cyl, but with the other engines I have seen, there is a scale with numbers. If you clean the area off, you may see these. Usually there is a mark at 0. This is TDC. Then you will see the scale is larger in one direction than the other. This direction is the scale for BTDC, and there is usually a mark for the factory spec of the engine, probably somewhere between 6-10 degrees BTDC.

The other direction on the scale from the 0 or TDC is ATDC. There will be very few if any marks in this direction, since ATDC is never used to time an engine.

 

and the little lines in between them should be in 2* increments.

Take some white paint and paint the line that matches your timing mark.
between the TDC and BTDC letters

That makes it easier for the Timing light to show it.

If you have a SPOUT connector ..that must be disconnected before static timng is done.

 

so I should use the first timing mark on the harmonic balancer (BTDC) and set it to 10 degrees. Make sure I am on the compression side TDC, make sure the distributor cab matches number one position, line up my prike marks on the distributor with the mark on the block. I should start. I am having trouble , we have went 180 back to TDC and still nothing. It acts like it will start, getting gas . I had the motor out - restored the factory paint, seal etc. Do you think it may have something to do with the painted surfaces not allowing for a good ground on my coil?

 

The OEM ground goes from the battery to the chassis where there is a bare spot on the cable that clamps to the chassis then procedes to the engine block where it is bolted to the front of the block (any size gasoline engine)

I doubt grounding is a problem if the OEM style cable was used and securely connected. Yes, there are other grounds, but that one is key, and if it were bad, the starter would not get enough juice to start the engine.

Any mark on the distributer to engine is almost useless if the distributer has been removed from the engine. The #1 piston must be in the compression stroke before the distributer is dropped into place with the rotor pointing to #1 wire. That must be verified first. Remove spark plug from #1 cylinder and hold your thumb over the plug hole while manually turning over the engine with a breaker bar. The compression stroke will push your thumb off the plug hole when it is near TDC. That is when you drop the distributer into place with the rotor pointing to #1 wire on the cap.

Wire brush the harmonic balancer edge. Use a strong light to carefully inspect the markings. At the very least, TDC should be marked zero or 0. Use a grease pencil, finger nail polish, or any permanet marker to tick that zero and time the engine from that point. Once you get it to run properly. Mark the spot with a larger tick to indicate your setting.

 

Doesn't this look like the one on your engine?


If so ...that Notch is your Timing Mark.

Mark it with with White paint.

 

No nothing like that - I do thank you for your help. I did get my truck running! I went ahead and set everything to TDC and it fired up. Before I was trying to set it a 10 degrees BDTC - the marks on my motor are etched on the balancer and the numerical numbers are on the timing chain cover. Thanks to you all

 

sweet... this thread may have helped me with my 86