Just Snooping Around Under the Hood

32witha409

Well Known Member
Supporting Member 3
Getting ready to install a new T-Stat. I have all of the parts to build a second water pump including an OEM cast iron impeller. My existing pump has had the bypass plugged and I could see wanting to replace the original bypass system at some point. Another question, with the available stamped impeller, anybody have any issues with them? Better, worse than the OEM design?
 

427John

Well Known Member
I believe the cast impeller to be a more efficient design capable of more flow when set with proper clearances but when a stamped impeller is equipped with a plate to close off the back side such as those offered by flow kooler for a while they will work pretty well.An impeller closed on at least one side will almost always be more efficient than an open impeller such as most stamped ones.Is the cast impeller you have larger diameter than the stamped one?In addition to the semiclosed cast impeller,the largest diameter impeller that will fit the volute area will give the highest flow.That was ususally the difference between the factory std. and max.cooling package water pumps.
 
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32witha409

Well Known Member
Supporting Member 3
Sorry John, should have just asked my simple question which was," Has anybody had issues with the stamped replacement impeller? Quite obvious that the stamped design is a compromise which is why I raised the question in the first place.

The OEM impeller across all of the 348/409 pumps that I have rebuilt from truck to PC all use the same impeller. I have never had the stamped impeller in my hands to interrogate.

Swapped out the stat, turns out the stat that was installed was a 160* Robert Shaw, and the gauge would stabilize at 180, with the 180* stat it stabilizes at 200-205. I now suspect the sender or gauge may be off 20*. Trying to find what the Moon gauge sender resistance scale should be. I read 100 ohms @ 200-205* on the gauge, while a thermocouple reference thermometer I use read 168 between the hose and stat housing.

The water pump is now leaking randomly.
 
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427John

Well Known Member
Getting ready to install a new T-Stat. I have all of the parts to build a second water pump including an OEM cast iron impeller. My existing pump has had the bypass plugged and I could see wanting to replace the original bypass system at some point. Another question, with the available stamped impeller, anybody have any issues with them? Better, worse than the OEM design?
If you didn't want the answer to that question why did you ask it?
 

32witha409

Well Known Member
Supporting Member 3
If you didn't want the answer to that question why did you ask it?
Well the part that might have confused you was in reference to the pump installed on a running engine, and any known or experienced issues, not the pump in a lab setting.
Simplify my future questions I shall, great master. :bow
 

427John

Well Known Member
The only thing that has confused me is why you asked if the stamped impeller was better or worse,when according to you the stamped impeller was obviously a compromise,and then get snippy when the question gets answered.
 

32witha409

Well Known Member
Supporting Member 3
A compromise does not necessarily dictate that it creates an issue in a particular application. As I'm sure you know, many refurbished, and new water pumps work well with a stamped impeller. That is why I asked this focus group who would know if a W block was effected by it. My compromise statement was double pronged, one is the cost to manufacture, the other is the design compromise comparo to the original.
I don't think I was snippy, blunt perhaps but not with any maliciousness intended.
No bad blood.
 
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427John

Well Known Member
A compromise dose not necessarily dictate that it creates an issue in a particular application. As I'm sure you know, many refurbished, and new water pumps work well with a stamped impeller. That is why I asked this focus group who would know if a W block was effected by it. My compromise statement was double pronged, one is the cost to manufacture, the other is the design compromise comparo to the original.
I don't think I was snippy, blunt perhaps but not with any maliciousness intended.
No bad blood.
Thats cool, the only problem I've ever seen with the stamped impeller pumps was corrosion due running straight water instead of 50/50,but they've been used for years and in most cases are adequate. In a rig that required max. cooling capacity given a choice I would choose the cast impeller.
 

32witha409

Well Known Member
Supporting Member 3
Finished going through the cooling system, Here is what I did
1) Rod out radiator, only found some red silicone sealer in the top end of a few tubes. Fixed a small leak at the top header. Other wise quite clean.
2) Rebuilt the water pump using an old cast impeller. Set volute clearance to .02-.015. It was previously at .075 +. Stamped impeller is about 5/8 smaller in diameter. The currently available seals install at .425" OA height including the seat. The iron impeller needs to be machined to .630 from .815.
3) Reinstalled the factory bypass and supporting fittings.
4) All new rad hoses.
5) Verified gauge reading with a decade resistor at various places. Reads low with test resistance values.
6) Verified all readings and sensor values to.
7) Installed a fan and matching thermal clutch of proper diameter and pitch.

Didn't effect the peak running temperature indicated. In these photos ~92*F ambient, It had reached about the shown temp and I pulled a steep hill under hard acceleration and the temp really didn't budge. The photos are just after the crest of the hill and the next few miles including a long down hill (higher vacuum shown). Temp basically moved maybe 1-1/2 needle widths down.
The readings from the drivers seat vs the photos straight on are higher do to parallax. I see closer to 210 than the 200. :dunno

IMG_4932.JPGIMG_4933.JPGIMG_4934.JPGIMG_4935.JPGIMG_4936.JPGIMG_4937.JPG
 

427John

Well Known Member
I was just looking on Flow Kooler's website and evidently they offer a rebuild service for hard to find pump castings and numbers matching pumps that includes upgrading to their high flow impellers,one of the listed apps is 348-409.
 

32witha409

Well Known Member
Supporting Member 3
I pulled the new Stant super stat and installed a new authentic Robert Shaw made (EMP-Stewart Components) 180* stat. Lowered the stabilized operating temp about 15*. Temp now looks like 185-190 on the gauge if. I can trust that. :wacko

John I had a high performance impeller drawn up already. I'll cnc one out of stainless if it comes to that.
 
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SSpev

Well Known Member
Supporting Member 3
The general function of a heat exchanger is to transfer heat from one fluid to another.


Again, the laws/formulas that dictate the thermal capacity of a heat exchanger are known and available in your basic thermodynamics classroom book. In non of them does dwell time reverse the formulas outcome. Further more in no case will increasing the flow of heated fluid (decreasing its dwell time) reduce the total thermal transfer of heat energy. The system will eventually bottom out and not improve, but it will not start going the other way. You will only thermally saturate the cooling fluid to the point that it can no longer absorb anymore heat.
Example below:
You have two radiators with all variables the same with the exception of the volume/velocity of heated fluid flowing through the core, one is 50% the other is 100% of the systems capacity. In the 50% low example, the mean coolant temperature across the core is 150* the other 100% example is
example the mean coolant temperature is 195*. Which example will transfer more heat energy out of the system? The 100% flow example because the mean Delta T is greater between the two fluids is greater.

Sorry to preach but these are basic system fundamentals, and I'm fine if we agree to disagree, this won't change my initial question. Off to work and then out to the garage. :p
Sorry m = mass flow rate. Flow rate does matter
Q = m.Cp. ΔTm
 

El Rat

Well Known Member
You can run a double water pump pulley with a dedicated water pump to crank pulley belt. This is a fool proof way to eliminate suspected “fan slip”. Obviously you need a three groove crank pulley.
 

427John

Well Known Member
Actually that is science,and contrary to what Liberals would try to tell us it doesn't change from day to day it remains constant because it is based on fact,unlike a theory or hypothesis which does not qualify as science until proven as a fact.Something that is touted as science cannot change because the act of changing proves it is not science.
 
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