V8 Bellhousing Alignment Fun

To start I bolted the bell housing to the block. I tightened the blots only lightly at first, but I had to snug them up to better control the bellhousing movement as I tapped it back and forth.

Basic tools needed for the job. 9/16″ socket for the bellhousing mounting bolts, a large socket to turn the crank, a sturdy hammer to tap the bellhousing and a dial indicator tool.

This is the little tool you need to align the bellhousing to the crank. The rear opening in the bellhousing determines the position of the centerline of the tranmission input shaft. This shaft should be very close to the center of the crankshaft rear flange. The tolerance should be as I understand it, .004 or less.

The parts I will use are the base with its magnet and the gauge with its adapter for the base shaft.

Here it is in place. As I turn the crankshaft (using the big nut on the front of the crank) the dial will slide around the smooth trans mounting surface. I’ve oiled the mounting surface slightly to make it smooth for the gauge tip. Also I only turned the crank in its normal direction – clockwise.

It took three attempts to get the job right. First attempt: I got the up-and-down set and then tried to get the side-to-side set. Of course the up and down got messed up. Tried this a couple of times and I couldn’t get it to work. Second attempt: I set the top to zero and then moved around the circle 1/6 of a turn at a time tapping the housing to bring the dial back to zero each time. Went around a few times, but couldn’t get it in line. Third time lucky: I sent the up-and-down close to zero. I then tightened the top center bolt on the belhousing to stop any further up-and-down movement. I then moved the dial to the 3 o’clock position and set it to zero. Then over to the 9 o’clock position and tapped the housing sideways to get to zero. Then back to the other side for any slight adjustment. Worked well and I have the tolerance down to less than .002.

Next I tightened up the bellhousing bolts and rechecked that the tolerance hadn’t changed.

I considered increasing the alignment pins to 3/8″ and using new pins, but I didn’t have any pins that were a tight fit in a 3/8″ bore. When I aligned the bellhousing on my 185 engine project I used roll pins. Unfortunately I didn’t have some larger (bigger than 1/4″) roll pins on hand. So I decided to do it by drilling and tapping for 5/8″ screws. I have a friend with a’57 Golden Hawk who did it this way.

Cast metal is not too hard to drill with a hand drill. I drilled two new 9/16″ holes in the bellousing block flange.

I drilled and tapped both sides inserted the bolts and checked the alignment. Something must have moved a bit because now it read less than .001 all around.

Next – problems!

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