Cam and driveplate timing?

[mattduncan]

Greetings,

We are in the process of a complete restoration and are having problems with the cam/driveplate timing marks.  Here is the info:

71 stag
Automatic 35

Here is the problem:

First off, it appears that the "timing" mark in the manual is only on the flywheel.  On an automatic, there is no flywheel therefore, no timing mark.  Second, when the machine shop removed the torque converter and driveplate, it appears he may have "marked" the driveplate where the timing should be. 

We can't seem to align the cam TDC timing marks AND the flywheel/driveplate timing marks.  When the cams are lined up, the pistons are hitting the valves making it impossible to line up the driveplate/flywheel timing marks. 

Questions:
How does one go about setting the timing for the #2 cylinder using just the drive plate?
How much variance can there be (timing tolerance) with the driveplate?
With an automatic, is it possible to use the driveplate as a timing indicator?

One other thought, we can get the "mark" on the drive plate to line up, but the LH cam is off by about 15 degrees.  I guess the bottom line is we can't find TDC on the number 2 cylinder (with certainty).

HELP!

[bobble350]

I marked TDC on No.2 with the heads off using a DTI then scored a mark on the front of the block to line up with the crankshaft keys. then set the cams with the groove to No.1 bearing cap (with a steel ruler), plus the jackshaft as per ROM. Fitted chains and tightened cam pulleys to the shafts. Never used the flex plate mark.
I test fitted everything first by bolting the heads onto Klingerite instead of head gaskets and checked piston/valve clearences with Plasticine.
If the cam is 15deg out I would guess the chain is out a couple of teeth.
You should be able to find TDC with a pencil through No.2 spark plug hole by measuring the piston depth either side of TDC.

I would suspect the machine shop marked the flex plate to replace the torque converter in its original position, not TDC.

Mark 

[mattduncan]

Well we had the piston at TDC, but we were not sure how "absolute" we needed to be.  I can get the piston to rough TDC, is that close enough?  What is a DTI?

Currently, we have the chains off in order to get the cams aligned/piston set.  We figured we would put them back on once timing is set.  We just had the heads rebuilt and tolerances checked so I know that portion is correct.    How close does the jackshaft have to be to the pictures?  The manual says to have the "lines" pointing just below the lower bolt on the LH chain support rail.  There doesn't seem to be any science to it and I can't see why the alignment would be that important.  It's only used to drive a worm gear.  Worm gears can't be "out of alignment".

[bobble350]

DTI - Dial test indicator. this can be magnetically clamped to the block and an arm holds a dial with a rod sticking out of the bottom that will measure to an accuracy of 0.001 ins. A quick surf should find a picture.

Are the heads on? easier if they aren't - you could use a straight edge across the block and feeler gauges to determine highest point of No.2 piston?

Accuracy - TDC is TDC the more accurate the better. Perhaps 1/2 deg either way won't make a vast difference.

You could fit the front cover and pulley. The pulley has a notch and the cover has a timing plate bolted onto it. This should indicate TDC to about 1 deg accuracy and should be acceptable.

The jack shaft does not use a worm gear.  It's not alignment  but angular position of the dizzy drive gear relative to the crankshaft. Anywhere will 'do' but you may run out of adjustment one way or the other when trying to set the ignition timing.  The jack shaft does not run at crank or cam speed.

Hope this helps.

Mark.

[wakaday]

Matt.
The manual has some good pics which should help.