I went to napa, brought my old wp for a core exchange. They said they dont do exchanges, just sell new. It was Napa brand, no idea where it is from, but it has a stamped impeller. I have heard the machined cast impellers are better than the stamped. If I go to Schucks would they have one with a cast? Should I just not worry about it? This is for a fairly hot 468. Thanks guys, Brett


I need to know before I paint this one because I dont think they will let me return it if it is black.. :noway:

bump, i know you guys know!

I think they're all stamped, the old ones used to be cast, but I don't know what year that ended.

NAPA sources their new water pumps from Airtex. As far as I know, Airtex and all other aftermarket water pump manufacturers are using stamped steel impellers. Actually though, stamped steel impellers are not a bad design. If the vanes are designed correctly to fit the housing, they will flow just as much, and possibly more, water than a cast impeller will.

Stamped steel impellers have also been used on Chevrolet OE water pumps for the past several years. However, with that said, it is common practice for automobile manufacturers to use OE parts from several sources to meet production deadlines, as long as the parts meet the engineering criterea. So is it possible to have two cars manufactured in the same year with different parts, such as water pump impellers.

Correct,i dont dont know the cutoff year but gm w/pmps used to have the better flowing cast iron impellers but for yrs now and MOST ALL NEW W/PUMPS UNLESS SPCECIFIED AS BEING HI/PERF/HI FLOW/30% BETTER EFFICIENCY HAVE THE CRAPPY STAMPES STEEL IMPELLER.

Evene a lot of the older gm castinge that came with cast impellers had stamped steel one installed when they were rebuilt.

But dont fret you can either buy an older original pump off ebay to have rebuilt of but a hi flow mildon or AL hi perf pump for better cooling.

But make sure to run a hi flow 180 deg stat with a hi efficiency/hi flow pump,its a must do.

When i changed from a w/pump with stamped steel impeller back to the older cast irom impeller i could see a noteable difference in coolent flow when looking in rad with cap off and reving the motor up,the cast impeller pumped a lot better/more force and the temp came down a few deg when hot too. This was with a mild 396/BBC.

Scott

Correct,i dont dont know the cutoff year but gm w/pmps used to have the better flowing cast iron impellers but for yrs now and MOST ALL NEW W/PUMPS UNLESS SPCECIFIED AS BEING HI/PERF/HI FLOW/30% BETTER EFFICIENCY HAVE THE CRAPPY STAMPES STEEL IMPELLER.

Evene a lot of the older gm castings that came with cast impellers had stamped steel one installed when they were rebuilt.

But dont fret you can either buy an older original pump with cast impeller off ebay to have rebuilt or buy a hi flow mildon pump with cast impeller or an AL hi perf pump with cast impeller for better cooling.

But make sure to run a hi flow 180 deg stat with a hi efficiency/hi flow pump,its a must do.

When i changed from a w/pump with stamped steel impeller back to the older cast irom impeller i could see a noteable difference in coolent flow when looking in rad with cap off and reving the motor up,the cast impeller pumped a lot better/more force and the temp came down a few deg when hot too. This was with a mild 396/BBC.

Scott

Thanks guys. I wonder though if you really need to flow the fluid that much faster. I have a good aluminum radiator so a standard stamped one may do the job.

Stewart makes good water pumps and great warranty with stamped impeller.

I'm running a new napa pump on my 454HO brett (the GMPP one crapped out after 300 miles) no problems at all- runs 180deg all day long, w/ a 3 core rad and no shroud....

hard to beat $60 for a napa pump when all the high perf ones are $100+

Good to know, thanks Ben.

Brett,dont chince out when it comes to a BBC cooling system,some people get away with the cheap inferior pumping stamped steel impellers,but some dont esp with bbc in 90+ deg temps,depends on particular setup/fan/radiator/cam/timing/fuel calibration/etc.

No avg street performance bbc will run 180 deg all day long as was stated with a 3 core rad without a shroud along with a stamped steel impeller pump in traffic on a hot/humid 90+ deg day,just aint so.

I could see 180 deg with same setup in 70-80 deg weather without much stop & go traffic is possible out in a more country/rural setting. But not 180 deg all day in 90+ deg weather in traffic with a street performance bbc esp with no shroud/inferior stamper steel impeller w/pump,and 3 core rad,no way IMHO.

I have also seen times where the stamped steel impeller pumps didnt work out well and people ended up chasing thier tails with cooling issues on hot 90-95 deg days when the stamped steel impeller pumps were not up to the task. The cast iron impellers have a higher pumping ability that is less prone to hot pockets of steam that can happen with the lower performing stamped steel units in hot weather esp in traffic with a bbc.

Pay the extra $30 to do it right the 1st time esp if your bbc with see hot weather and stop/go traffic at times. It would be real shame to have cooling issues later on when you couldnt track it down all because you thought your new/cheap stamped steel impeller pump was doing the job ok when it really wasnt up to the task /couldnt handle it on a hot/humid 90 deg + day .

Make sure to also run a 180 deg hi flow stat if you decide to use the Milodon or an AL hi perf pump,its a must with a high output w/pump.

Scott

Thanks guys. I wonder though if you really need to flow the fluid that much faster. I have a good aluminum radiator so a standard stamped one may do the job.

Brett,

You are correct, the speed that the fluid is circulated is not the determining factor in keeping an engine cool. In fact, that is exactly why an engine will usually overheat when the thermostat is removed. The coolant needs to "dwell" in the radiator for a sufficient time for the heat transfer from the coolant to the atmosphere, via the radiator . If the coolant is circulated too fast it will have travelled through the radiator before it is sufficiently cooled.

Cooling problems can usually be cured by paying attention to the radiator frontal area, fan design, thermostat operating temperature and shroud design.

Bill,

That is good to know. This means I will be fine with my fancy pants aluminum radiator, shroud, and 7 blade fan. I will paint my water pump tonight then.

http://www.stewartcomponents.com/cgi-bin/yabb/YaBB.cgi?board=tech;action=display;num=1161703901

Common myth, busted.

Yes sometimes when people remove the stat you can run hotter due too unrestricted flow. But with a hi flow pump & a matching hi flow 180 deg stat that sets up a retstiction(not wide open with unrestricted like with no stat) thats when the the hi flow pumps out perform the stamped steel impller pumps hands down.

It isnt all about coolent flow speed,its also that the hi flow pumps with a little higher pumping pressure eliminate or reduce the hot steam pockets that form when a motor(esp bbc) heats up in traffic which adds to cooling problems/overheating that the stamped steel impeller pumps with lower pumping pressure cant handle.

I pasted below the real scoop on higher flow pumps From Stewart Pump mfg that know what they are talking about ,not just an opinion.
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This is a common misconception. Higher flow will always cool better than slow or low flow. It's what we refer to as turbulent velocity. This is needed as the coolant passes through the radiator. An indication of not having sufficient coolant flow is uaually noticed at lower engine speeds which slows the pump speed and results in the loss of turbulant flow. The result is higher coolant temps. This is why the Stewart hi-flow water pumps work so well. These pumps are designed to increase/maixmize coolant flow even at low engine rpm/road speed.

Constant flow and pressure is necessary for the coolant fluid to effectively transfer heat to the atmosphere via radiator core and fins. Pressure keeps the fluid in contact with the walls of the radiator and flow keeps the cooled fluid in circulation back into the engine, replaced by heated fluid from the engine. The fluid must, however be moved in a controlled manner. If the fluid is moving too fast, or too slow, the effectiveness of the radiator will be compromised.

High flow water pumps (whether they use a stamped or cast impeller) do an excellent job of keeping the fluid moving and pressurized. Thermostat and bypass hoses, if used, do the job of keeping the fluid travelling at proper speeds to ensure proper dwell time within the radiator.