Oil pump sizes?

I am replacing the oil pump (the old one was for a semi-auto box) with a standard pump. The pump I was sold as a 71 on is not deep enough - the body of the new pump is 21mm deep (including the shaft and everything that actually goes inside the engine is 44mm) The old pump is 5-6mm deeper overall thus engaging with the slot in the cam shaft properly. Have I been sold a pre 71 pump? My engine code is AH (8/71-1/76). I one catalogue I have looked in it says count the rivets holding the gear - is this what I can see when I look into the oil pump hole and turn the engine over? (I have 4).

PS thanks for all the help I have received from this group, it is quite a steep learning curve sometimes, hopefully one day I will have enough knowledge to be able to offer some help back.

The earlier engines came with a flat 3-rivet cam. All high performance cams are made in the 3-rivet -style.

Later model cams are 4-rivet type, with a deep dish in the middle.

So... later model cam and cam gear need a late model pump that goes deeper into the case. You were obviously sold an early type pump.

You can make the early type pump work however, the shaft of the driven gear is just pressed into the gear: you can punch it out a little further, so it reaches the cam. It won't turn, but it will slide in and out with the help of a friendly hammer. You also need to make sure that the suction and pressure side holes of the pump line up with the case holes.

I suggest you still try to get the proper model pump though. Much easier and no risk of breaking stuff.

Jan