Before you put an HEI distributor in a HD 67-early 80's (maybe later) C40-70 GM Truck with a 350/366/427 flip

it over and look closely at the oil pump drive and compair it with the old one. It is different than the normal dist gear that are in cars

and light trucks C10-30 and of course the pump shaft is different too. Why GM did this is anyones guess.

This guy didn't.

We have an old 10-wheeler, 1975 Chevy C-70 tag axle with a 366 and 5x2. It was needing a tune up. We

decided since we we were going to put cap, rotor, points, wires and plugs in it why not go a little farther

and replace the old distributor with an HEI and see if it helped performance. Son in law went to the local

O'Reilly's and told them what we had and what we wanted to do. "Got just what you need right here. Now be

sure and compare the length to be sure it fits"

He brought it home, compared the length, it was identical. Put it on, started right up. Built up air

pressure, drove down the road to see how it worked ... and about 100 yards down the road the motor just

stopped. No noise, no warning, just stopped. And it wouldn't even crank over. Fortunately a neighbor came

along and helped him drag it back to the shed before the air bled off. Like most of us he was listening to

the engine and didn't notice what the oil pressure gauge was reading. We got to thinking about it and pulled

the distributor out. The gear on the bottom is identical on the outside. Inside the end .. the oil pump

drive ... it was made different.