Aquamist Water/Alcohol injection Installed

Verifying the TDC mark on the harmonic balancer

The following method of verifying the TDC on the harmonic balancer was explained to me by Paul Burke over the phone.

Because the harmonic balancer (HB) is from a E34 and the pistons are JE and not OEM, Paul wanted me to verify the TDC mark. Here is how I did it and what I found.

First of all, I thought about using a dial indicator.

Only problem is, the piston is at TDC for longer than a set point. You can actually move the HB while the dial indicator is 0 ed out. This is caused by the clearance stacking and the fact that it takes several degrees of rotation for the rod to go over center. (Clearance stacking is the result of the wrist pin to wrist pin bushing, and rod to crank clearances) So that was a no go.

First, buy some big ass washers and bolt them in opposite corners to the block. Make sure the block is clean and scraped with a razor blade.

Now I was hoping that these washers would act as a stop but they did not. The piston can easily bend them up on its way to TDC. So I used a .005 feeler gauge to continuously check the gap as I very slowly moved the piston towards the washers.

Once the gap was closed I made a mark on the HB. I then turned the HB so the piston was touching the washers from the other direction. I marked that spot on the HB too.

So if the OIT mark on the HB is correct, the distance from the factory mark to the marks I made on the HB should be the same on either side.

They were not. I measured 14mm on the left and 10 mm on the right of the factory mark. So my true TDC is 2 mm to the left of the factory mark. This is where I will set the HB when I dial in the cam. Paul is making making me an adjustable cam gear so the cam to crank timing will be perfect.