Line it up on the dowel pins...
Line it up on the dowel pins in the block.
Unfortunately, most factory service manuals are good for theory but don't give the tolerances or instructions for adjusting the housing. Speaking of factory parts, those units won't contain a clutch or flywheel explosion like an SFI-approved bellhousing. Stock units are OK for stock usage, but when racers take their engines up to 9,000 rpm, that's asking for quite a bit of protection from cast aluminum.
If we've scared you enough to consider dialing in, you have only one more hurdle to clear, and that's the alignment pins on the block. They can cause some of the same problems that core shifting causes. They can also be a problem if they have been pressed in with more than the usual 0.001-inch tolerance, but that's manageable, too. They are the main components for aligning your bellhousing, so you'll need to make sure they are in good shape.
Follow this simple procedure and you'll sleep a little better knowing you're not shaking your driveline to death every time you put a lap on it.
Use the block and bellhousing you plan to race. Do this anytime you swap these components. If you're using a block plate, put it on first. (If you're not using a block plate, you're shortchanging your protection. It's a simple 1/8-inch steel plate that's part of the system. It helps contain problems and even keeps the clutch and flywheel clean from track debris.) Install the flywheel and housing you want to use. It's easier to mount it up without the clutch assembly, as you don't need it for this procedure. With the crank in the block, tighten up all the fasteners on the bellhousing. Torque the 3/8-inch bolts to 35-40 pounds. Now check for paint buildup on the inside diameter or register bore of the housing. If any is found, use an emery cloth or a scratch pad to smooth out any high spots. Mount a magnetic dial indicator on the flywheel, making sure it can turn it 360 degrees inside the bore without contact. The indicator's plunger should just touch the inside diameter of the housing. Rotate the flywheel and read the gauge.
If there are high spots of...
If there are high spots of paint inside the register bore, take them off.
As you are measuring a circle, remember misalignment is one half of the indicator reading. It's best to always use the same location spots as you go through measuring and fitting. The Lakewood personnel who showed us how to do it marked the 12:00 and 6:00 locations with their readings. If the reading is within tolerance of 0.005 after checking twice, you're ready to go racing.
If there is an off-center condition, select the offset dowel pins that are closest to your measurement. Lakewood makes them in 0.007-, 0.014-, and 0.021-inch sizes. (If the reading is 0.016, divide by 2 to get 0.008. The closest replacement dowel pin is 0.007 inch.) The first step to put them in is removing the bellhousing.
Removing the stock dowel pins can be accomplished either by driving them out with a drift from the front of the block or using gripper pliers and pulling them out. Once removed, clean out their bores and coat them lightly with a thin lubricant. If the holes are too tight, you may have to ream them to be ready for the 0.001 press-in difference that is needed.
Your bellhousing should look...
Your bellhousing should look like this with all the proper hardware in place.
Lubricate the new dowel pins and install them into the block. The slot end of the pin should be the one exposed. The direction of the slot indicates the maximum offset. Both pins should always be installed parallel to each other and in pairs (i.e., both 0.007 inch, 0.014 inch, or 0.021 inch). Use two screwdrivers to align the pins with the housing loosely mounted to correct the tolerance discrepancy. Tighten the bellhousing to specs and check for runout. To make any adjustments, you'll need to reposition the dowel pins, still using the slot as a reference. This involves trial and error. Tighten up the bellhousing and check it again. Repeat this procedure until you are within tolerance for best results.
For those who must routinely take their bellhousing on and off the same engine, a weld-on dowel pin kit is available. Just dial them in and then weld them.
The key points to this simple procedure are:
1. Measure the actual pieces you are using.
2. Keep tolerance at 0.005 inch.
3. Divide the dial indicator reading by 2.
Do it like you'd turn a lap-consistently and smoothly-and you'll ensure your driveline has a chance at a long and productive life.