High Volume Water Pumps / Electric fans.

[mike huddart]

Dear Tinka, I think its something like 10 degrees, but depends on rad design.I will see if I can find the book of words! Regards Mike

[Sidecarbod]

Originally Posted by purge98

Why would you want to stall the airflow?

Surely you want as much air passing through the radiator as possible.

Stalling the air or at least getting it to slow down allows more time for the air to pick up heat from the fins. In fact the fins usually have feathered edges to create extra turbulence. The problem with a lot of rads is that they have too high a fin count per inch, and not enough coolant tubes. Manufacturers do this because tubes cost more than fins! The problem with a high fin count is that once a certain speed is reached the rad just won't flow anymore air, it will create stand-off and spill round the sides, you can block off the sides which will help but you will still reach a point where the stand-off builds up so much that the air won't go into the rad opening in the bodywork, it will spill round the car instead. This can happen at quite low speeds, i.e. 40 mph. At this point you are relying on the fact that the rad should have some "reserve ability" to cool the engine at lower speeds which is used up at higher speeds.

I read most of this in a book; I'm not claiming to be a wiz on aerodynamics, thermodynamic, hydrodynamics, or any other "dynamics" that you care to think of.

In fact the book describes the rad as a funnel, it states that the rate of oil flow through a funnel is controlled by the small hole at the bottom not by the big hole at the top or not by how quickly you pour the oil in the top, if you do pour it in too quickly for the hole at the bottom to pass, it just spills over the top.

HTH,

Pete

[wilf]

Roger - I think the clue to your problem lies within your post.

If you don't normally have cooling problems, then can we assume that you were using extended high revs on your trips around the LeMans circuit?

The problem might not be water, but oil cooling - sbfs can make a lot of oil temp at high revs under some circumstances. Any high oil temps would eventually be reflected back into the water cooling system,and if that does not have enough "headroom" capacity, then you get overheating.
Do you have an oil cooler fitted?

The other point could well be too much coolant flow at high revs - try fitting a larger diameter pulley (sometimes called an underdriven pulley) to slow down your water pump.

Lastly, too little flow could also be an issue - is there anything apart from Mike's suggestion about hoses sucking flat ( a very likely cause btw) in the system that could restrict flow?

One thing at a time though.........

[ti]

The problem might not be water, but oil cooling - sbfs can make a lot of oil temp at high revs under some circumstances. Any high oil temps would eventually be reflected back into the water cooling system,and if that does not have enough "headroom" capacity, then you get overheating.
Do you have an oil cooler fitted?

Hi Wilf

About your above comment - Do you know what the oil temp should be ? As mine runs at about 110 degrees with an oil cooler fitted. 351 cleveland.

[queeniee]

Never had any overheating problem with my big block. I use an Edelbrock water pump N° 8805:
"These Edelbrock Victor series high-volume water pumps are designed for maximum flow and equal coolant distribution in street cars, racecars, tow vehicles, and motor homes. The aluminum pumps have CNC-machined housings with special one-way internal passages that flow more coolant at higher velocities, even at low engine speeds. The CNC-machined, cast iron impellers are larger than other impellers, and have curved vanes that produce greater flow with less cavitation. Other features include heavy-duty roller bearing assemblies built to withstand higher torsional loads, billet steel hubs, and leak-proof seals. Plus, most Victor series pumps are available in your choice of natural cast, polished finishes, or Endurashine."

the cost was $165

[wilf]

Ah but Queenie - you have a big block, and they need all the water flow they can get!

Terry - 10 degrees above coolant temp is the norm, so you should be OK, so long as it doesn't climb much higher when you give it some beans. I find mine is very rev-dependant - on a track it gets v hot indeed, on the roads it never gives any problems. (oil temp that is, never have an issue with water temps). Do you have an oil 'stat?

Also, remember that automotive gauges are notoriously inaccurate, especially electric ones, it could be worth checking what temp you really have with a thermocouple type electronic meter.

[dodger]

Thanks for the suggestions lads.

I'll have to go through each possibility one by one.

Yes, Wilf we were giving it a bit of stick at extended high revs on the track I suppose, however there is an oil cooler & stat fitted.

On the trip down there we were cruising at times at 90-100mph in the cool of the early morning. However, that was in 4th & 5th gears & not on full throttle.
No water loss whatsoever.

I'll try & blank off the gaps at the sides/top of radiator first & buy an infrared thermometerto see what the temp is at various areas of the cooling system.

Mike Huddart mentioned sucked flat hoses to the pump inlet from the bottom of the radiator & the worst culprits being silicon hoses. Has anyone else had experience of this ? ?

I know some hoses have a coiled wire inside them, is that the best option ?

Regards,

[David Large]

Dave N quote,

"(normal running temp around the 40deg mark on a warm day like today)"

Don't know a lot about all this but isn't a temperature so low a bad thing?
Isn't that why we have thermostats, to stop the temperature being too low?
On a really cold day, my RV8 might run down at 60 deg and I am not sure I really like that.

Cheers

[craggle]

I too have heard of bottom hoses being sucked flat. Silicone hoses are surprisingly soft and a good water pump can easily suck one flat to the point it will no longer flow. More likely to happen when the engine is cold as the cooling system will not be under any pressure like it is when hot.

I used stainless tube for as much of the pipe run as possible and then joined to the rad and engine with short silicone elbows.

If this was the problem you should be able to see it if you rev the engine from cold and watch the bottom hose.

Craig.

[Martyn-ak427]

Regarding Dave N's post;

There is an old, but recent post on hear which discusses the detrimental effects, (bore wear I think) of running an engine too cold, I think Wilf knows a bit about this subject..

I have applied the same logic as Craig in the fact I have limited the use of silicone hosing to elbows & short runs preffering the rigidity of stainless tube for much of the top & bottom radiator connections.

Incidentally (& excuse the sales pitch & post hijack) but I have a 1.5M length 38mm O/D, 36mm I/D 316 polished stainless steel tube which I used for my cooling system & is surplus to requirement for sale.

Regards,
Martyn