Corkscrew

It is a cylinder .842" long by .373 in diameter. Main body is shiny steel but both ends are black steel with a slight taper at each end.

Nowhere Man

a little clue on to where you found it and year of car your working on. to me it looks like a under sized 3/8 dowel pin. unless you measured it wrong

plaidside

When I sold an early small block water pump last week there was a dowel just like that one in the bag with the gaskets.
Joe

MasterDave

1) Bellhousing to engine dowel

2) Cylinder head to block alignment dowel

3) Dowel, dowel, dowel.......

Corkscrew

Joe, I think you nailed it. I had several things stored in a box, one of which was a new water pump, which I have already mounted, sans this thing, of course. Anyone know its purpose?

ifitgoesfast

Yep, nice guess on water pump.

Looks like it's for aligning the two halves of the water pump covers front/rear, mostly marine applications where you have to clean it out from salt intrusion, rebuild. Other than marine applications, scooters and dirt bikes had water pumps made from two cast halves, so you needed one or two dowels to align the halves; the dowels had o-rings to seal.

JohnZ

That dowel plugs the bypass hole between the passenger-side leg of the water pump and the engine block on cars that use a water pump with a bypass fitting and hose to the intake manifold (like the 326 pump).