Jacob,

I have a 228 GMC and that triangle is used to check the valve timing. In the past gears at times were not marked (as the story goes) and you had to count the teeth on the cam gear with the piston at TDC (UDC or UIC mark on the flywheel). If the mechanic put it together correct that mark would align correctly.

Here is the proceedur:

1 Engine at operating temperature

2 Crank engine until #1 intake valve closes and the UDC mark (UIC) on the flywheel is in line with the pointer.

3 Place a .002 thickness gage between the valve stem cap and rocker arm.

4 Continue turning engine until all lash is eliminated.

5 If the valve timing is correct the pointer will be aligned with the triangle on the flywheel.

I tried this and it does work. You should never have this problem.

You should be able to align the pointer and ball with the vacuum diconnected and pluged. The engine should idle okay, if not check for vacuum leaks around the carb or intake.

I hope that helped,

Jim

Jim