[49dream]

I want to put a chrome water pump on my 350 SBC more for the looks.
A salesman at yearwood said the chrome ones don't last because the heat won't disapate through the chrome. Is there any truth
to this. I found a Polish alluminum pump for $ 75.00 through a speed shop on the Net. But no guaratee. At least the chrome one has a Year guarantee. All the other places want's about $140
for polish alluminum

Any help will be appreciated

Marcus

[willys36@aol.com]

Don't worry about a chromed one failing early. That is an urban legend - heat transfer from polished chrome is of the same order of magnitude as any other finish. Also, the temperature of the pump (and the critical seal) is @ water temperature, regardless of what material it is made from. Buy whatever one you want and run it with pride!!

[camaroman7d]

I would personally go with a polished aluminum pump. If you want chrome to last you must keep it clean and dry. If you don't it will start to look bad in a short period of time.

The part about heat disapation, I am not so sure I really buy that. It could be true since chrome is a series of coatings. I think the problem would be more from the lack of texture than from the fact that it's chrome.

Royce

[RCastle]

Same thoughts here. If it has a year warranty on it go for it.Some do not even carry that.Get what you want,if it goes bad,they are easy swaps,plus it is warranted.

[VWFan]

Willys - Are you sure about the heat???

The reason I ask is because coming from the air cooled world I have always heard that the chrome parts will not dissipate the heat as well as say black parts. I am not sure if this is true, but I have always heard that. VW owners are pretty attentive to heat problems and I would think that they have tried almost everything to keep the old VW cooler, to include running tests between chrome vs. non-chrome. I'm not trying to argue, I just want to double check the info....

[camarochas]

I had three chrome pumps on my 350 Z28 and when the engine was revved high two of them blew out the front and one out the rear. After inspecting them I noticed that when they are chromed it appears that the plating is done first and the bearing bores are not machined after the plating. I believe the bearing takes a better press if the surface is not chromed. Anyway, that's my experience with chrome pumps. I now have an Edelbrock aluminum waater pump on a BB Z28.

[RCastle]

VW Fan-On the water cooled engines the water pump just circulates the coolant,sure chrome may retain heat but the radiator coils actually cool the flow.The water pump will not affect the heat that much.

[VWFan]

RCastle - I understand how the cooling system on a water cooled engine works, but I guess my question should have been does chrome really hinder heat dissipation? In this case the water pump would still be subjected to heat from the block etc. If the chrome pump retains heat wouldn't that cause undue heat stress on the pump, possibly causing early failure? I'm sure that a chrome pump works the same way as any other, but could the heat cause an issue IF the chrome does in-fact reduce heat dissipation?

Does that make more sense?

[RCastle]

Dang computers,I was not calling you uninformed or dumb bud.The water pump really won't retain heat to much as the flow is continuos.I do not see the water pump wearing out from heat damage too badly.Heck if a Harley can have an all chrome engine,be air cooled and not self destruct within 25 miles,the water pump surely won't.I can see that the bearing failure from the plating process being a possibility though.

[VWFan]

No offense taken! I was just trying to clear up MY confusion. So, since the pump will have constant flow of fluid there is little chance that the heat would be able to build up enough to make a difference.

....But....I still would like to know, for my own information, as to whether or not chrome really does retain more heat.

Willys - What do you mean when you say "order of magnitude"?

[willys36@aol.com]

Originally posted by VWFan
Willys - Are you sure about the heat???

The reason I ask is because coming from the air cooled world I have always heard that the chrome parts will not dissipate the heat as well as say black parts. I am not sure if this is true, but I have always heard that. VW owners are pretty attentive to heat problems and I would think that they have tried almost everything to keep the old VW cooler, to include running tests between chrome vs. non-chrome. I'm not trying to argue, I just want to double check the info....

Technically you are right. A perfectly shiny surface would emit zero radiant heat while a perfect black body would emit gobs of radiant heat. Chrome is a very good imitation of a perfect shiny surface and the radiant emissivity is very low. However, the amount of heat radiated is also a function of the distance from the hot body to the 'cold' body to the 2nd power and of the temperature difference between the hot body and the cold body to the 4th power. None of those values is very significant in this case. That is the only heat transfer mechanism that would be affected by the chrome and anyway, a polished aluminum surface would have a similar radiant heat transfer rate so there is no benefit to either.

There are two other heat transfer mechanisms acting on a water pump - one being convective transfer of heat from the hot metal surface to the air blowing past it. That is a function primarily of the difference in surface temperature of the metal and the temperature of the air blowing past. True a smooth surface like chrome or polished aluminum transfer less heat than a rough cast surface but again, not much difference to even worry about it in any pump you might buy. The last mechanism is conductive heat transfer from a hot body to another in contact with it. Aluminum is a better conductor than iron or nickle but again, the heat transfer rate is strongly driven by difference in temperature between the hot and cold body. Since the water pump is virtually the same temperature as the engine block which is the only thing it is in contact with, nothing to worry about here either.

A nice glossy thick paint job is much more detrimental to heat transfer than a metallic chrome surface.

In summary, yes there are obviously differences in potential heat transfer rate for different water pump materials but I would bet a dollar to a donut that the difference in pump temperature at the seal, which is the only part I can imagine that would care about what the temperature is, would be quite insignificant. Heat transfer in a water pump is not a concern to automotive engineers and is insignificant in the grand scheme of things. You could perfectly insulate a water pump from it's surroundings (actually, with some of the big, close fitting water pump pulleys they put on some cars, that is in effect what is happening to some pumps) and it would last as long as one that was cooled as well as possible.

[VWFan]

Cool! Thanks Willys, you answered both of my questions!!! Now that I understand what you are saying it clears it all up!!!

[49dream]

I have been going for two hours and was not expecting
this kind of response. Thanks for all your help. I am going with the polished alluminum. Why: The post on replacing 3 chromed ones and The post on keeping it clean convinced me.

Thanks

The hot Rodders Rock again.