Looks like I need a new water pump. I've been looking for a replacement, and I see that there are two different height options...3 31/32" or 4 15/32". I'm not clear on where the measurement is taken. I assume I start where the pump bolts to the engine...but do I go from there to the end of the housing, the face of the hub, or the end of the shaft.

I'll try to attach a pic with the different measurement options on it. Do use measurement A, B, or C?

That pic isn't very big. Here's a link to the picture:

Water Pump

im pretty sure its B

It's D. From the outside of the top bolt hole to the leading edge of the snout.

If you are good with a measuring stick, you'll see the dimensions to be spot-on.

I have the 3-31/32 pump, it's called the short, I use a 2" spacer
and the fan barely makes it in the radiator shroud.
My fan needed another 1/2" to 3/4" to go 2/3's of the way in the shroud. Maybe this will help.

Well, the parts supplier I use brought in each pump, just to be sure I got the right one. We held them all up side by side and the longer one was a match for my car...which I think is 4 15/32 (basically 4.5").

So, I sat down and set my calipers to 4 15/32 and tried to figure out where that dimension comes from. And with the pump off the car and on my desk, I can't find any dimension that matches it. Because the pump is off the car, I couldn't check Amervo's option D...but it looks like that would be it. Which seems like a very weird dimension to use. Seems like you'd want to use a dimension that you could check with the pump in your hand...but hey, what do I know?

The Ames catalog shows what would be Option B in my picutre...but according to what I have here, and what came off the car, that's not the correct way to measure it. It's about a quarter inch off.

Just thought I'd update this in case anyone else was wondering.

im sticking with b i just went out and measured all 3 of my pumps from the bolt surface to the outside surface is 4 inches. if you add the thickness of the water pump and measure from the flat gasket surface to the outside of the hub it comes up to about 4.5 inches. Thats close enough to 4 15/32

So your right to as d+15/32=b so b= 4 15/32"
As long as I’ve been doing engines, manufacturers always use a known always constant measuring point. That in this case being the gasket surface to the outside fan hub mount. It’s the only measurement that makes sense. That would always put the outer hub surface in the same place after a rebuild. Sure enough I went out with my calipers and a flat surface ,bam gasket surface to outside surface of fan mounting hub all 3 = 4” 15/32
give or take a 32nd

I haven't taken one of these pumps apart...beyond taking it off the car. But is the hub a constant point? It looks like there is a shaft, with the hub on one end, and the impeller on the other end. I imagine there are a couple bearings in between. It looks (and I could be wrong) that the hub is press fit on the shaft. If that were the case, I think that maybe the hub wouldn't be a constant point. I would think the best, constant points would be the gasket surface to the end of the snout (option C). I agree that "opton D", which takes the entire bolt holes on the engine into account would be a goofy option...but it's the only one that matches on the pump in my hand. It's a reman pump...maybe it came off a different car.

At this point I just want to get it back on the car. The pump didn't come with a divider plate and mine is a little rotted. so I have to wait for a new divider plate. I was hoping today, but no order acknowledgement from Ames yet.

yes thats what i meant the constant is the gasket surface LOL not the hub! So when the pump is built the outside of the hub will be pressed into the impellor until its = 4 15/32" from the gasket surface, not the other way around.
The shaft doesnt matter at all just as longs as its completly engaged with the impellor and hub. That way they ensure the fan mounting point is always the same. its B!
I just saw you live in new england i go to ames every friday, well keene anyway. its B! lol

just bookmarking this page...looking at a pulley