3782609 water pump - application?

[Dan Pepper]

What application is this pump for? This particular pump has a March '66 date code. Will it work on a '69 350/350?

[Joe L.]

Re: 3782609 water pump - application?

Dan------

Are you sure it's not a 3782608? In any event, both 3782609 and 3782608 waterpump castings did exist. The 3782609 was used during the 1961 to 1963 period for Corvettes with external bypass. Consequently, it has a large boss on the top of the casting which is drilled and tapped for a 1/2" NPT fitting. These were used on Corvettes with aluminum intake manifolds.

The 3782608 pump was first used in the 1961 model year, too. It is a similar casting, but it lacks the large boss on the top. It was used for engines with cast iron intake manifold and no external bypass provisions. This included passenger cars and Corvettes. This is also the casting that was used on all 1969 Corvette small blocks, so it would be correct for a 1969 L-46. It was used through 1970 for Corvettes (through 1968 for non-Corvette small blocks).

The '608' castings were manufactured at both Saginaw and Tonawanda. The Tonawanda castings have reinforcing ribs on one side and a "T" on the casting; Saginaw castings do not have these features and only Saginaw castings were ever originally used on Corvettes. The '609' castings were manufactured only at Saginaw.

[Joe L.]

Addendum

By the way, if what you have is actually a 3782609 casting, it will work perfectly for a 1969 L-46 application but it's not NCRS/NCCB correct for such an application. Functionally, the 2 castings are the same except for bypass provisions. For a non-external bypass application you would simply plug the fitting on the top with a pipe plug. Many SERVICE waterpumps require this, too.

You also need to make sure that the pump has the INTERNAL bypass hole clear. This is the "third" 3/8" hole (below the bottom bolt hole) in the passenger side leg of the waterpump.

[Dan Pepper]

It is a "608" w/cruddy casting numbers...

The last number in the casting is smudged/filled, so looked like it could be either an 8 or 9 (more 9...), so based on the presence of internal bypass and no boss, it's a '608. So now it's going on the car this week;) As usual, Thanks, Joe.

[Dennis C.]

Almost worthless afterthought...

the '609 pumps that I'm familiar with on 61/62 applications carried no casting date.