I am installing the distributor drive shaft back into the spiralled gear on the cam. The manual, on page 9-97 says to ensure that piston no. 1 is on tdc of the firing stroke. I know TDC, how do I tell if it is firing or, I assume the opposite is exhaust stroke? TDC is always firing is it not?

 

Yes there are 2 TDC, one is the Firing and 1 is the exhaust.

It is simple, but a little time consuming, is to pull the valve cover and see if the exhaust valve is open at TDC on the crankcase at the #1 cly. Then you know you need to go to the next TDC or not. Both will be closed on the firing stroke at TDC. Don't forget to pull the ASD relay before you touch the key (So the injectors don't spray any fuel).

Or

Pull out #1 plug and the ASD relay. Then bump until you get to TDC. Install the distributer. Set up the rotor to hit the #1 spot on the mark. Put it all back together. Then try to start. If it doesn't start flip the distributer 180 Deg. You have 50/50 shot from the beginning.

Or

I guess another way might be to get a compression gauge and install it on #1 cly and bump the engine around. Don't forget to pull the ASD relay. On the exhaust stroke at TDC the compression will be way lower then the TDC of the firring stroke due to the exhaust valve being open.

I'm sure you have it but this picture will help if you don't.

 

Well, this is throwing me for a little loop. Everytime I am at TDC, both valves are closed on the number one cylinder. I can see the exhaust valve open just before one TDC, and the intake valve open just after the next.

Oh, and it helps that I have the engine out of the vehicle on a stand, should have said that before.

 

I think I got the alignment right, I am at TDC, can't say if it is firing TDC or not.



Looking at it closer, since the groove in the top of the distributor drive is flat and seems symetrical, even if I did set it in at the non-firing TDC, I can always make up for it by making sure I am at TDC firing before I set the distributor on, correct?

 

Just did this on my '95 3.9L. Put the mark at TDC on the balancer. Have someone turn the motor over by hand with a ratchet and socket on the crank bolt. He'll have to do it a few times. With #1 spark plug removed, put your finger over the plug hole. As he cranks it over you'll feel the suction on your finger as the piston goes down - INTAKE STROKE. As he continues cranking, you'll feel your finger being pushed off the hole - COMPRESSION STROKE. As the piston moves down the bore again you'll feel suction - POWER STROKE. As the piston moves back up the bore your finger will be pushed off again - EXHAUST STROKE.
There's a fairly noticeable difference in pressure between the compression and exhaust stroke. You want the compression stroke. When you feel the compression stroke, stick a small, thin screwdriver down the hole and let it ride up slowly, until the piston is at the top of it's stroke. That's TDC on the compression stroke.

Also, the slot in the top of the distributor shaft must be pointed at the first intake manifold bolt on the drivers side. From your pic, it looks like it is.

 

Well, I will have to copy the excerpt from the Magnum rebuild book I have. I figured it out. The book says that your firing TDC is when both the intake and exhaust valves are closed throughout the rotation. Everytime you are at TDC on cylinder one, they are closed. But on the other TDC, the non-firing one, the exhaust valve opens just before TDC and the intake opens just after TDC. This is not the TDC you want to set your distributor to. Form what I understand.

By the way, when setting the distributor, you can turn it to line up with cylinder no. 1, any idea of what the tolerance is?

 

It is to be dead on #1. But if it is off a bit, like 1/8 of an inch on both sides it would be okay.