55 water pump trivia

[Roy B.]

I've talked about the first and second design parts for the 55 Corvette like=

Distributors
Carb linkage
Headlights
Radiator shielding

Now water pumps, the original's has no top casting for a water outlet (left pic) that later replacement design did (right pic) but no real outlet for a fitting and they both have the same #3704911 and will fit under the original engine support.

This can be determined buy useing your finger between the engine support and pump


Dist also had the same # numbers but first design (top pic) second design (bottom pic)

[Jack H.]

Re: 55 water pump trivia

Drilling & tapping the upper boss for an external bypass elbow was a secondary operation on the roadway leading from a basic core casting to a finished PN for the complete water pump assy.

To my way of thinking, it's a bit unusual to make such a big design change in the core casting (going from having NO upper boss to a pump housing with an upper boss) without changing the cast number itself... But, I don't know what constituted a change big enough to warrant a new, separate, cast number at GM in those days...

I can't say I've every see a '911 pump drilled and tapped for external bypass, but I HAVE seen the casting that replaced the the '911 housing (3736493) which was.

The '493 pumps that I've seen with external bypass were drilled & tapped for a small, 3/8-inch NPT, bypass elbow and were installed on various mid/late 50's Buick and Caddy engines...

[Roy B.]

Re: 55 water pump trivia

Drilling & tapping the upper boss for an external bypass elbow was a secondary operation on the roadway leading from a basic core casting to a finished PN for the complete water pump assy.

To my way of thinking, it's a bit unusual to make such a big design change in the core casting (going from having NO upper boss to a pump housing with an upper boss) without changing the cast number itself... But, I don't know what constituted a change big enough to warrant a new, separate, cast number at GM in those days...

I can't say I've every see a '911 pump drilled and tapped for external bypass, but I HAVE seen the casting that replaced the the '911 housing (3736493) which was.

The '493 pumps that I've seen with external bypass were drilled & tapped for a small, 3/8-inch NPT, bypass elbow and were installed on various mid/late 50's Buick and Caddy engines...

Jack! I always look forward to read your comments like other that don't even own a 55 but show interest, I don't think but two other guys here even have one. I feel like a lone person at times. I've seen 55 having the wrong WP with that boss casting thinking they have the original WP because it has the correct #911 number. I just like to see as many 55's be correct that the JM in (MY) opinion will never address (in my life time) . We all have a pet Corvette ,mine is the 55!

[Ted S.]

Re: 55 water pump trivia

Roy, When did the second design of the distributor come out? I have an original late '58 and it has the second design.

[Roy B.]

Re: 55 water pump trivia

Roy, When did the second design of the distributor come out? I have an original late '58 and it has the second design.

Then it must have been replaced , it was only used in early 55 Corvette and Car, you need the second design using the same part#

[Ted S.]

Re: 55 water pump trivia

Thanks Roy. By second design I meant the top one in the picture. So the bottom is '55 only. Thanks for the info

[Roy B.]

Re: 55 water pump trivia

Thanks Roy. By second design I meant the top one in the picture. So the bottom is '55 only. Thanks for the info

Yes it's early 55 only, what # when it changed I dont know that , that's what needs to be decided
Like many of the second design parts ,it's a guess ,one would think that all the second design parts came on line around the same time or serial number.Seems #400 might be the point. Then again there are so few 55's left we may never know for sure