How to find 0 Degrees TDC for T-Belt Replcmt

[BurbankJalopy]

Thanks in advance for all of your help. I'm changing my timing belt and belt tensioner on my 81 FI 2000. As you know the crank timing tab is pretty vague on this model and so I'm trying to verify that I'm at 0TDC with the crank, before I put the new belt on. My plan to verify the crank is at the right position is as follows; take out #4 spark plug and put a wire or something straight on top of the piston, then rotate the crank and watch for the piston movement to stop at the highest point, and if there's rotational slop while at TDC, I'll assume zero is just as it stops upward motion. This should be 0TDC. I'm 99% sure of this theory, just not so sure of using #4 cylinder as opposed to #1 cylinder to prove it. My distributor is pointing at #4. Before I took it apart I got it close to the timing tab on the crank, then used the cam pointer to stop at just the right time. If the crank is off at all, it is just a degree or two. I just want to be sure that I've got it all lined up, as one of the cam gears seemed like it was a tooth off. I've got the cams and aux shaft at the right place, just need to be sure on the crank. I don't have one of those degree things (degree wheel?) to use.

[narfire]

I have a 80 fi as well.
Before taking the old belt off, I'll take the plugs out and turn the engine over till the cam wheels are lined up,or close to the markers/ line on the cam towers.
On the passenger side of the engine, I hope you have a marker down low that has a pointer with three ... points on it that sits just over the alt.water pump belt wheel on the crank. There is a small indent on this wheel and should line up around those three marker points. I've put a small dab of white paint on the indent to help these tired eyes see the mark better with the timing light.
I've had to loosen the marker to get the old belt off as there sometimes is a very small clearance to squeeze the old/new belt through.
Line up the cam marks just right and 0deg. or small marker for the crank. put new belt on. I saw a tip here where you put the belt on the ex cam and then clamp it with a c clamp or something. snug over the int. cam and try to put the belt on the crank without moving the crank, marks should still be at 0 deg. I found one tooth out there was a difference in the car,it worked but worked better when I had it just right.
I'm not sure about the pulling plug stuff, but I'd like to think the marker is there as one end of it has a pressed in bolt/stud.
A bit long winded I suppose but it works for me..
Good luck.
Chris

[majicwrench]

Don't bother with the wire down the plug hole, you will never get close that way. The piston will be virtually motionless for several degrees as it nears, then passed, TDC.

The factory marks, although vague, will work just fine. Assuming the car runs correctly now, just carefully mark (I use white paint) the pulleys in relation to some stationary object. Mark all the pulleys! then with new belt on, marks should still line up. If you must find absolute TDC..........

Pull #1 or #4 plug. Now build yourself a special tool. Take an old sparkplug and remover all the pocelin part, right down thru the plug. Remove ground electrode. Removing pocelin not easy, hammer and punch, wear eye protection!! NOw put a long 1/4-20 bolt or piece of thread-all thru plug housing and secure with a nut on bottom, and on top if need be. You will have to grind the edges off the nut or it will be too big to fit into the cylinder head plug hole.
Now you should have a plug with a 1/4" adjustabe stud sticking down an inch or so. Insert into #1 or #4 with piston down. Gently roll engine clockwise till ;piston contact stud. Stop and mark balancer. You need some sort of stationary marker on block or timing cover. Now roll engine gently counter-clockwise, till piston contacts stud. Mark balancer.
Exactly half way between those two marks you just made is TDC .

Gently is the key word here, do not force anything, as on some engines I suspect the valves may interfere with the stud, although I have yet to have that happen.

Recommend just using factory marks.
Keith

[So Cal Mark]

there is a casting line on the front seal retainer that matches up with the crank sprocket for tdc