Ok so the Z marked it's territory in a parking lot yesterday, and the water pump is shot. The good news is it never got over normal temp and I drove it home a put it back in the garage. I'm considering the $65 Summit water pump that says 30% more cooling capacity. Right now the car is bone stock ,but I've already got a 650 Holley, and a 3.42 posi rear, and by January it will have the carb installed with a new intake, a set of headers and true dual exhaust and the rear will be installed. The point is i'm slowly modding the engine, so I'm wondering if I will need the "30%" extra that the Summit water pump says it offers or will just a $25 stock replacement work just fine? It will realistically be years before I get to serious mods on the engine. The only other thing is if I drive it on the interstate in steaming hot summer weather, it creeps toward hot, yet it will idle all day long in the same weather without the guage moving. Maybe a new water pump will resolve this? Feel free to throw suggestions out.

The stock one has worked fine for millions of small blocks, including all those factory high output engines. All of them work good enough that the thermostat needs to close for awhile, so they all pump more than sufficient flow.

A lot of people don't realize that coolant needs a little time to absorb the engine's heat. It needs to briefly dwell within the engine to absorb this heat.

Sure, radiators are more efficient with more flow- but the tiny passages in a radiator guarantee all flow is laminar. Flow through the block is turbulent if not restricted, and speeding up the flow often increases the turbulent flow in the front of the block while flow in the back of the block stagnates, leaving hot spots.

No additional coolant flow is necessary. Street engines are more difficult to cool than race engines because of stop-and-go driving, iron heads, smog/EGR, low airflow due to low speeds, A/C, etc. and the factory cooling system is very well designed. You could spend that money on something much more benficial- like a tune up.

<font face="Arial,Verdana" size="2">Originally posted by Douglas Staley:
A lot of people don't realize that coolant needs a little time to absorb the engine's heat. It needs to briefly dwell within the engine to absorb this heat.</font>

Where does this logic (or lack there of) come from? http://www.nastyz28.com/ubb/rolleyes.gif

Let me clarify.

The coolant does need more time to sit within the engine to absorb heat and reach operating temperature (hence a thermostat), but it does NOT cool the engine any better by flowing at a slower rate.

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350CID, Vortec 062 heads, Magnum 280, Performer Intake, Holley 650 DP, 3.42 rear w/ Auburn posi, 2600 Stall/TC
"Things are more like they are now than they ever were before."
Former U.S. President Dwight D. Eisenhower

[This message has been edited by AJ_72 (edited July 25, 2005).]

Undergraduate engineering heat transfer and thermofluid mechanics.

When flow is too fast, i.e. bordering on becoming turbulent, eddy currents start to flow anywhere straight-line flow or rough surfaces exist- such as the complicated passages in an engine block. The flow is forced through so fast that much of the flow concentrates on the shortest path between the entrance and the exit and completes this path without mixing with the hot water already resident toward the back of the block, because this is the only places that the flow can remain somewhat laminar at these flow rates. Sure, there is still flow everywhere else, but there is a boundary layer that contains eddy currents that do not transfer heat effectively. Sure, the water is cooler this way, but the whole point of the cooling system is to regulate the temperature of the interior metal casting material, and this is optimized when you have fluids flowing closely against the internal surfaces. If you force the coolant too fast, you'll generate vorticies and other similar tirbulent flow that doesn't contribute tto the cooling you need because the existing coolant is spinning in a small localized circular current rather than moving out of the block.

This is why high output engines have restrictors added to the block deck. By ensuring the water is flowing slowly enough to guarantee laminar flow, the fastest laminar flow will give you the best cooling- but once it goes tirbulent, you get hot spots because you create vorticies and similar flow patterns that don't contribute to cooling the surfaces insulated by the eddy currents.

One of the best performance improvements you can make to the cooling system is to install a decent aftermarket water pump. Stock pump are poor on bank to bank distribution and rebuilts are down right horrible. I am sure you will be happy with the Summit as I suspect it's made by one of the many aftermarket suppliers.

Thanks for the replies guys. Still not sure exactly which way to go. Rick, I will absolutely not use a reman pump, so whatever I decide, it will be new. I've got some time, first of all it's not the DD and also it will take some time to get the front of the block cleaned up enough for paint and detailing, so keep the comments coming!

My suggestion, get the Edelbrock pump, it costs a bit more, but the quality is really good.
The Aluminum vs steel knocks several pounds off the nose of the car.

<font face="Arial,Verdana" size="2">Originally posted by Douglas Staley:
This is why high output engines have restrictors added to the block deck. By ensuring the water is flowing slowly enough to guarantee laminar flow, the fastest laminar flow will give you the best cooling- but once it goes tirbulent, you get hot spots because you create vorticies and similar flow patterns that don't contribute to cooling the surfaces insulated by the eddy currents.</font>

And that restrictor is called a thermostat.

Keep in mind we're talking about a street driven car. The coolant flow is slowed any time the car is sitting at idle (e.g. stop light). The 30% in flow helps to move the coolant through the radiator more quickly, correct? And the t-stat will restrict the flow through the block if by chance the coolant gets too cool, correct?

I can understand if we were talking about a race application, but afaik we aren't.

I am not a big fan of taking out the thermostat. I have NEVER found a car that required this on the street. What's the difference if the coolant is at, say, 210*, between a properly sized restrictor and a wide open thermostat? I submit there is NO difference.

At the strip? Yes, sometimes. Temps come up fast under a WOT run and the stat can't react fast enough (takes time to heat up and open), causing temps to often be much higher through the traps than it is at the starting line. Using a restrictor instead of a stat can often keep the temps more constant from the beginning of the run to the end.

Try taking a 180* stat and leave it out in the sun to bake at, say, 110* on a hot day. Then drop it in a pot of boiling water and hold your breath. You'll probably turn blue before it gets wide open.

Doug- thanks for the info about coolant flow. I never heard a really good explanation of why you needed some restriction in the system before, but I'll definitely buy yours.


[This message has been edited by Damon (edited July 27, 2005).]

I too say stick with a stock water pump. Unless you want the bragging rights of saying you have an Edelbrock water pump to everybody. I'm no undergraduate student of thermodynamics but I have real world experience to offer. If for example you have a very efficient radiator capable of keeping your engine cool in all types of hot weather, either aluminum or copper/brass, once the thermostat opens, all you are doing by moving the coolant faster through the radiator (30% more flow, right?)is giving the radiator less time to shed the heat. If you have overheating issues, the solution is not a faster flowing pump-it almost never is. The answer is a more efficient way of shedding heat. More power builds more heat which means you need a better radiator or an improved way of shedding the increase in heat, ie electric fan. I have no use for aftermarket pumps even though they are nice. GM didn't go clammering on Vic's door for a high flowin' pump when they designed the LS6 454 Chevelle. They built a HD clutch fan and went to a bigger radiator. -Jabin

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Gmachinz Sales and Performance
"...updating the level of performance..."

[This message has been edited by gmachinz (edited July 29, 2005).]

What Douglas said. I agree 100%. The question about the aftermarket water pump is a little more tricky. At what point does the flow become turbulent? Does it happen when you add a Eddy pump? I don't know - complicated analysis. I do know that I run a Victor series pump and my temp. stays 195 +/- 3 deg all day long whether it is 20 degrees outside or 120 (using a 195 thermostat). Would it do the same with a stock pump? Probably, but there are other reasons for using a victor pump besides increased flow.

[This message has been edited by Goat (edited July 29, 2005).]

I'm sorry if I came off sounding arrogant or boisterous, I certainly didn't mean to. Consider a few things that support what I was trying to say.

A high volume pump will move water more quickly from the radiator into the engine, and aftermarket pumps may be more capable of improving the balance of flow between right and left banks- I don't know anything about how effective or crappy stock pumps may be at this. I don't know if race mechanics try to "port" or otherwise improve flow capacity of any pumps- maybe they do, I have no idea.

The Summit pump is probably a good quality pump. If you feel that you are overheating because you can't move coolant from the radiator to the engine fast enough, this will probably help. If you find your thermostat isn't defective or damaged (opens and closes when it should) and it never closes because water isn't moving fast enough, the high flow water pump will probably help.

However, most of us have run across the occasional thermostat that gets stuck open. This almost always causes a street driven car to overheat. After all, if your engine requires constant flow to remain cooled, what happens when the ambient temperature rises another 10 degrees? What happens if you find a way to make another 20 horsepower? Your temperature keeps going up in either case.

The 2-row or 3-row radiators in our GM engineered cars are capable of cooling the factory engines with smog equipment, full-tilt A/C, underhood insulation, relatively poorly maintained vehicles (compared to the way we maintain our machines) etc. at Death Valley temperatures. Most of us have lost the insulation, aren't sitting still in endless traffic jams (although some of us are), have removed the smog equipment, we maintain our vehicles, and don't drive in Death Valley. Many of us have also gone to a 3- or 4-row radiator. Sure, our engines are modified to produce high-performance, high-power output, but very rarely is this power potential tapped- power output 99% of the time is within original design limits (whenever we aren't near full throttle). If these cooling systems were so marginal when new, wouldn't warranty costs have driven GM into the ground in the 70's?

I am just suggesting that the OEM water pump is less marginal (at least by design, not necessarily in the best condition after all these years) than many people give it credit for. GM puts the same pump in base models that it puts on the most demanding engines (at least when they share the same block design), such as Police, commercial, truck/towing, etc. applications.

After all is said and done, a high flow water pump will move water from the radiator to the engine faster, at least while the thermostat is open. If everything is working correctly, this means that the thermostat will be open for a shorter period of time since the coolant is swapped more quickly. However, since coolant flow in a thermostat equipped vehicle is intermittant rather than constant, does this provide more cooling capacity, or simply more power drain as well as higher financial cost?

For what its worth, I used to have to drive around town staring at the temp. When I finally broke down and bought a Stewart water pump, I have never had another problem with my water temp. Im not sure if 30% more flow actually means 30% faster???? Perhaps it means 30% more complete? Im just saying for a few more dollars, you can make it right once and for all and never have to worry about it again.

MaTt

Trust me Doug, an aftermarket water pump is far superior to a standard production pump and you can't even compare it to a stock rebuild. You can have a 70/30 split on stock pumps bank to bank is the general thoughts.

It is a great performance upgrade.

I appreciate all the discussion here. As always seems to be the case, budget came into play here, and I went for a new stock pump. I will definitly upgrade to a better one as the engine mods require. I hated to do it, but then again it was less than $25 so no great loss even if I upgrade in a year.

That does make a lot of sense if flow distribution is the problem. The stock pump has always been well capable of flowing enough coolant that the thermostat always closes (after which the pump dead-heads and cavitates, so there's no more flow) but evenly distributing the flow may be another matter entirely since it's completely unregulated, and may be subject to many casting variations and inconsistencies. I've not found any problems with flow capacity on stock engines (even those most difficult SBC applications- motor homes with a van chassis, full-tilt AC and smog when towing) but the back-and-forth flow tendencies of the SBC are well known.

Thanks for all the discussion here ya'll. Natually budget came into play here, and I wound up buying a new stock replacement. I'ts on an the front of the engine is detailed, (you know us car guys can't just slap a new part on without sprucing up some!). I hope to get all the other stuff back on tomorrow nite. I only spent $25 on the pump, so no big deal, but I will definitely upgrade when modifications dictate the need.

This has been a great string. Perhaps the only item not mentioned and worth throwing into the soup is the pump material. If the "30%" higher flow pumps don't violate Douglas' well thought out principles they can be bought in aluminum and for drags every couple of lbs you can shed from the nose can help. I think theres enough field experiance that A: Its pretty well recognized that the aftermarket pumps balance of flow is superior. B: Certainly on street class hot rods there seem to be no downsides to the "higher flow" aftermarket pumps either. Lots of folks use them.

For me the flow balance and 6-7lbs of weight saved out front and I'll spring for a good aluminum pump.