Oops! 96 4.3 timing mistake

I just dropped a freshly rebuild 4.3 V6 into my 1996 Blazer. When I built the motor I had everything set at TDC, but like an idiot I turned the motor over to torque the driveplate bolts and completely forgot to drop in the distributor first. I've built several motors and this is the first time I've done something this dumb (I'm kicking myself right now).

Question:
I've set it back to what I believe is TDC, but just to be sure, which of the two marks on the balancer is TDC? IIRC it's the second mark that is a few inches counter clockwise of the first mark.

When I put the motor together, I dropped the distributor in while it was at TDC so I could align the oil pump shaft so the distributor would just drop in with the motor in the car. I removed the distributor prior to dropping in the motor in order to provide easy access the upper tranny bolts and to prevent damaging the dizzy. When I set the motor to TDC after my mistake, the distributor did not "just drop in" with the motor set at either timing mark on the balancer.

Anyway, I guess if it doesn't start I'll just reposition the distributor until it does.


Thanks in advance!
(no pun intended)

Do you have a piston stop? That's an easy way to find TDC. If not, careful probing with a screwdriver can do it.

Remember that if this is a W series engine, you'll have to phase the cam position sensor with the CKP, so correct distributor position is somewhat important.

There is two TDC's.on a 4 cycle engine.
exhaust stroke TDC is one.
You need to find compression TDC.
Hold a finger or a compression gauge over the no 1 cylinder hole to find TDC compression stroke.
Then bring it up to TDC on the marks.
Then set dist as shown here.
http://files.automotiveforums.com/gallery/showphoto.php?photo=51302

After engine is started and running you need to find a scanner and have the camshaft retard setting set.

Thanks for the info, but I'm well past the point of needing to know which TDC and where the rotor should be pointing.

I pulled off the 1,3,5 valve cover so I could take a peek at the rocker arms to determine if #1 was on the compression or exhaust stroke. The motor is currently set to what I believe is TDC with the rotor pointing at the "6" mark.

When I assembled the motor, one of the marks on the balancer lined up with the pointer on the timing cover when the motor was at TDC, now I am unsure of which mark lined up.

What I'm trying to figure out is: which mark on the balancer is TDC, or which way should the woodruff key be pointing when the motor is at TDC?

Oh well, I plan to fire it up tomorrow, if it doesn't start I'll just reposition the distributor.

Thanks for the help.

The woodruff key is cut in the crank snout at the 0º position for the #1 crank throw. That's where they've been since Ed Cole decided to stop using pressed on, unbolted balancers and bolt/key them to the crank.

Hook up a scan tool tool and the spec is 0 degrees.Look for cam sensor retard in the engine data stream.Start it up and shut off making sure it is 0 degrees.

I would think that anyone with experience would know which mark. I wasn't aware there were 2 marks. Last resort would be sticking coat hanger in cylinder and rocking it to get tdc. If the marks are an inch or so apart it should be very apparent which is correct.

Just in case this helps someone else in the future, the TDC mark is in fact the mark that is a few inches counter clockwise from the first mark.

I assumed that the first mark is used when setting the timing with a timing light to **BTDC, and that the second mark is the actual TDC. Apparently this was a correct assumption since it fired right up on the first try.

The timing is not adjustable on it.
Turning the dist only centers the rotor to plug wire terminal.
After you get the dist set where it is running you will need a [engine capable] scanner to set camshaft retard setting.
It needs to be set as close to - or + 0 degrees as possible.