This Spanish guy says, on slide 7, says impellers with 5-10 blades are most efficient...

https://www.youtube.com/watch?v=mfb0ydtdr_M

I've found an explanation of backward, forward and radial (orthogonal) blade design here: http://www.learnengineering.org/2013/03 ... -pump.html

It turns out that power consumption changes with each as a function of the flow.

For backward curved blades, pressure decreases with higher flow and power consumption stabilizes with flow. In radial blades, pressure is constant with higher flow and power consumption increases linearly. In forward curved blades pressure increases with flow and power consumption increases exponentially. So, backward curved blades are preferred industrially, because of the power consumption stabilization.

Whether this matters with coolant at the RPM's we're talking about is another story. But I feel better at least knowing something about all those angles.

brian

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I thought the 8 blade pump would have better low RPM flow. Good for lugging / towing a race car with a truck. That is what I am using.

Rick

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

...but if there are any substantive differences, at low or high rpms, it's silly that the vendors don't mention anything about it...

if you go to RockAuto, click on waterpumps for Sl6 and read the "info" buttons, they say things like:

Airtex: "The latest impeller upgrades engineered for maximum coolant flow"

Cardone: "Hubs and impellers are precisely perpendicular to the bearing shaft to eliminate excessive bearing load and noise"

Pronto: "Premium metal or plastic impellers are designed for optimal coolant flow"

Gates: "The precision balanced impeller increases water flow, and extends seal and bearing life"

AC Delco: "Precisely positioned fan hub"

Only the Cardone unit shows a picture of the impeller (8 blade forward angle).

FYI,

Brian

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The Gates one says, "The no-sealant-required gasket allows for fast, easy installation"

Do you all use sealant on your water pump gasket or not? I do.

brian

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That's what I would have thought,at lower rpm as in the normal slants operating range it would make sense... but who knows, at the end of the day they all seem to do a decent job. Dan mentioned the 6 blade pump may have been preferred and that may well be the case.....there was a post here somewhere but can't find it now!!

No, it was to prevent flung crud from clogging the weep hole. Factory pumps had this weep hole shield starting in 1964.

Dan,I have no doubt this is also a possible use for the cast in shield/scupper drain/smiley face/whatever on the water pump....but I've gotta ask...where did you get the info from for the shield being used to prevent the drain hole becoming blocked?? You have obviously spent a lot of time researching all things slant six,but that's taking it to a whole new level!

From Doc

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Interesting. The slant water pump not only sucks in coolant, it sucked me in. I was surprised by how much thought could go into responses about the various pump designs.

Sam

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Not an "also possible" use, it is the intended purpose. Sorry to seem pedantically insistent on this, but it bugs me when guesses get repeated until they turn into "common knowledge".
Former Chrysler Corp Chief Engine Engineer Willem Weertman's "History of Chrysler Corporation's Slant-Six Engine", volume 1, pages 33-34.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Does anyone not use sealant on their water pumps? brian

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I am running for my dictionary!!

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

I'm not sure a guru like Dan can actually be pedantic; after all, we come to him for the details in the first place...

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No apology necessary I was merely curious where you get this info from...that's not really my area of expertise or interest in our hobby,but it's great that others are...whatever floats your boat! Happy sailing if that's your thing

Twenty years ago I had a 68 Dart 273 with AC and found a difference in impeller vane count between the non AC and AC cars.

I checked into that to find out why there were less impellers in the AC water pumps.....turns out that the thinking was to reduce HP drag on the car engines that also had to push AC units.

Kinda goes is the face of a concern of overheating car engines pushing AC units in the hot summer?

So my question would be did anyone ever compare 70's slants with AC to those without AC for impeller vane count?

I know my 65 parts manual shows same impeller for AC and non AC for the slant.

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

True. In '72, for example, the 318 and the 340 got a ø4.38", 8-blade impeller without A/C, or a ø3.7", 6-blade impeller with A/C. The driven (water pump) to drive (crankshaft) pulley ratio is 0.95:1 (underdriven) without A/C, 1.2:1 or 1.3:1 (overdriven) with A/C.

So the non-A/C cars had a larger, more-blades impeller spinning slower than the crankshaft speed, while the A/C cars had a smaller, fewer-blades impeller spinning faster than the crankshaft speed. What does this tell us? It tells us the primary intent was to spin the fan faster in an A/C car than in a non-A/C car, to make sure of pulling enough air across the condenser and radiator at idle and low road speeds so that the A/C would work and the engine wouldn't overheat. The smaller impeller with fewer blades spun faster would have kept coolant flow about the same as the larger impeller with more blades spun slower.
Mmm...nope, don't think so. Whoever told you this was misinformed, guessing, or pulling your leg. Overdriving the water pump/fan pulley means considerably more drag than can be compensated by the difference in water pump impeller diameter and blade count.
From the factory, all Slant-6 engines got 3.5", 6-blade impellers except the 1960 170 which got a 3.25", 6-blade impeller.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.