Something is up here. You should have absolutely no problem getting the distributor set to tdc. Ideally, you want the no. 1 plug wire at about the 5 o’clock position. Take a look at the photo of the motor. Take note of the position of the various clips and studs. Set your distributor so the no. 1 wire is at the correct position on the cap. Then put a vertical chalk mark on the body of the distributor directly under the no, 1 tower.
Take the distributor out. Loosen the screw or bolt on the clamp. Use a flashlight and look into the block and see where the slot is on the oil pump. You need to get the distributor in so that the tang engages with the oil pump and sets the distributor in so the chalk mark is at about 5 o’clock. Does not have to be perfect. This might take a couple of tries and you may have to use a screwdriver to move the slot a bit to get the distrib7tor where you want it.
Make sure it’s fully seated. As HRL noted, it is possible to get the distributor in and the motor running without having the tang seated in the oil pump groove. You will know this immediately when you fire the motor but have no oil pressure. If this happens, shut the motor down and srptart over.
If it’s fully seated, install the hold down bolt, center the octane selector plate and tighten it down. Then, install a rotor and rotate the distributor until the rotor is pointing directly at your chalk mark. Tighten the screw on the clamp. Install the cap. Install plug wire no. 1. Check to see that all of the other wires are in the proper order on the cap. You are at near perfect tdc. Fire the motor, check the oil pressure, then time the motor with a timing light to perfect tdc or even a few degrees of advance, 3-8, see what the motor likes.
