Sheared wheel studs and cooling issues

[gmsclassics]

Racing last weekend at Taupo came to an abrupt end when two studs sheared off a rear wheel. Fortunately the others stayed on but both were very bent and stretched with the wheel flopping all over the place! Some years ago I replaced the standard ones with M12x1.5. Maybe overtightened, maybe heat stress, maybe hitting too many curbs, maybe 1cm wheelspacers, maybe very tight LSD setup?

Weather was extremely hot and car was running at indicated water temperature of up to 120C, even with a spray system from the washer bottle. Only lost a bit of water though but have now noticed the (4 row) radiator has given up.

What else will fit, yet has markedly more heat dissipating capacity than standard? Alloy and bigger! Need some help here as there seems no point in simply paying a lot of money to recore like with like. I've always been at a loss to understand why a Sprint has the third hose coming from the radiator. Can anyone explain why it is there and exactly what the water flow is around the rad / engine. What will be the impact of replacing it with a simple two hose radiator as this I suspect would increase my options of donor vehicles. Would you run a bigger alloy radiator without any fan? No fan (even electric type) would possibly allow a thicker radiator to be fitted.

Geoff

[jeroensprint]

Hello, the thirth hose connection on the thermostathousing has a very tiny hole in it so it is not for circulation. It is also located above the thermostat so it has nothing to do with warming up. I think its for a better cooling system fill. I run a dolomite with a two hose radiator and that's no problem at all. Some late tr7's also don't have a thirth hose and that's the same engine. Don't worry buying a two hose radiator.

About running with no electric fan is not a good idea. When you turn your engine off after racing it will get hotter for a period and than you have no cooling. When you have a healthy sprint with good waterholes in the engine and a good waterpump you do not need a very very big radiator. Does your head match the engineblock? Sometimes the waterholes do not line up and than there is no good flow.

Jeroen Rothman

[SPRINTPARTS]

Hi Geoff,

High ambient temps are always going to be struggle for a racing Dolomite. Thankfully our racing season starts in March and is usually ended by October/November, before the heat arrives, but we can still have 35C to deal with sometimes.

I run a 50mm thick alloy radiator, same core as V8 Supercars, but unfortunately a lot smaller in size, ie standard Dolly size. I also use an electric water pump and electric fan. The water pump is manually controlled via a speed controller, and the fan and W/P can be switched on using a timer system to run after the motor is shut down, which helps with quick cool down after a race.

I am also using a synthetic coolant, which has a boiling temp of 190c. This does not help keep the motor cooler, but it allows high engine temps with no concern of boiling the coolant out of the motor which is what will destroy a motor.

Thankfully we have not run in any high temps for a while, the last meeting I competed at (Nov '08) which was in the new car, had an ambient temp of around 28c and the motor ran around 90-95c while pushing hard. The difference in temp between 6500 rpm limit and 7000 rpm can be +10c. Philip still uses a mechanical W/P, 6 vane I think, and never seems to have any major issues with coolant temp.

I believe that the small top radiator hose can be deleted, I think that it was to help eliminate air pockets in radiator. I have not had it confirmed, but it has been suggested that a Porsche 944 radiator might be a suitable replacement.

Good Luck and let use know what you decide to do.

Mark

[gmsclassics]

Been to see a couple of radiator specialists.

First one, recommended as being the best repairer, said he can fix my original easily. Also said that this style of core can get blocked very easily and doesn't respond well to backflushing. He said he will put it through his ultrasonic cleaner which should work wonders (interestingly we use one of these in the hospital sterilising unit as the first step in decontaminating surgical instruments).

The other, who does a lot of work for racecars is giving me a quote for a re-core. His comment was that while dense fins on the core (16-18 per inch) are good for road cars, they can slow down airflow at speed. They recommend a more open core with fewer fins (12 per inch) so that the increased airflow at speed can pass through the radiator and remove more of the heat. Sometimes they even put baffles in the tanks on each side of the radiator effectively dividing the core into three sections, forcing the water to flow quickly back and forth making three passes through the radiator. Both of these ideas were new to me. I might go this way, but it could prove an expensive experiment as I expect it to be in the NZ$6-800 range.

Both said that there is no perceptable difference between copper and aluminium radiators and neither recommended changing to the latter.

Your comments, Mark, about the effect of increased revs rings very true. At Pukekohe my gearing works well for a 6500 rev limit, while at Taupo I found that going to 7000 was the only way around many of the corners without losing momentum. I did try using overdrive on second but I'm always scared that will blow the box! Taupo was where the temperature got out of control.

Geoff

[trackerjack]

Its a pity that the pump cannot be slowed down because it sounds as if the damn thing cavitates when the revs go right up, has any one tried grinding off a few blades on the impeller? Try 3
I think that that is why the six vane is better more vanes less efficient.

[DavePoth]

Its a pity that the pump cannot be slowed down because it sounds as if the damn thing cavitates when the revs go right up, has any one tried grinding off a few blades on the impeller? Try 3
I think that that is why the six vane is better more vanes less efficient.

I read somewhere that the works team used the 12 vane pump with 6 vanes cut off.

[SPRINTPARTS]

There are lots of theories on 12 vane vs 6 vane pumps, some of which appear to have merit and others which could best be described as urban myths (read bulls**t). Some facts and finding as I know them-
A few years ago the stag Owners Club conducted what I consider to be the most scientific test of the two pump designs in Stag in an environmental test chamber with a rolling road. The results showed that at normal engine and road speeds there was little difference in the two pumps cooling performance. However at idle the 12 vane was measureably better than the 6 vane. At higher engine speds there was some advantage displayed by the 6 vane but it was marginal. Their conclusion was that for real world use on the road the 12 vane was preferable because of the advantage at idle speeds.

The matter of the water cavitation at high engine speeds in my mind is debatable. I have 6 vane impellers that have been reduced in height, presumably to reduce coolant flow, but I have never used them in any of my race motors. I have always stuck with the standard 12 or 6 vane impellers. Both of which I have used and I struggle to identify one as being better that the other. It is worth noting that in Aus we race in ambient temps up to 40 deg C (thankfully not very often) and up to 70% humidity at that temp. Cooling of the driver becomes more of a challenge than the engine.!!!

Jeroen makes a very important point- the size of the water gallery in the block between the pump cavity and No1 cylinder water jacket needs to be big enough to allow two medium sized fingers to fit through it. The clearance between the top of the impeller vanes and the top cover is also very important. Too close is as bad or worse than too large a clearance.

Philip

[jeroensprint]

Hello, some more theories.

The hole between pump housing and cilinderblok must be around 4x3cm. Most early blocks have very small holes. I had a block once with a hole of appr. 1,5x1,5cm. That engine must have had cooling problems in the past.

Very importand check the head matching the block. I made an "mastergasket" usable for sprint and 1850. When doing an engine i put this gasket on the cilinderblock and match the waterholes with this gasket. After this i put the gasket on the head and also match the holes. Often they dont match. Do not match the holes who are blocked by the small holes of the gasket. These little holes are only against airlocks. When you enlarge these holes the internal flow will disturb and the engine will get hotter.

Not matching is also the stag cooling problem. Some v8 cannot keep headgaskets and some can run for years with no coolingproblems. These owners are very happy that the factory accidentally fitted heads that mach their engine.

Waterpumps is a different story. The six vane pumps very good and is oke for normal or fast road driving. On my holliday to italy with caravan and 35 degrees a six vane works well. Only for race engines a 6 vane at high revs pumps to much and builds up to much resistance. A 12 vane at high revs and a thick gasket is better for the jackshaft.
At idle i do not know wich is the best. The manual of shimming with gaskets is not neccesary. Always use the thick one.
There are two types of 6 vane and their covers. Do not mix them up. They look alike. There are 6 vane with full vanes and 6 vane with 3/4 vanes.

Jeroen Rothman

[Hans ten Broeke]

It is possible that the works teams did alter a 12 vane into a kind of 6 vane and because the vanes what than be left over have probable less capacity than the original 6 vane design.
But for sure the works F3 engines (what they called a stand up version), did use a stock 6 vane impeller with a special pump cover what have a bigger volume.
The complete F3 engine I own have such a pump, and we use 3 of them also in our racing engines.

If a pump created to much friction, because for example a to small clearance between the cover and the impeller, you can run in all kind of trouble.
I have seen razor sharp, or partly cheered of teeth, this also create extreme pressure on the jack shaft keeper plate, braking the oil film of this very blunt shaft location system.
Partly the same happen with a to high pressure oil pump.
Next to that it will create axial play in the jack shaft what on its own create ignition timing failures.

For the radiator we found a rather simple solution, using a Porche 944 aluminium rad what has the connections on the same place as the Dolomite rad. this rad is light, easy to obtain, and resemble priced.

Till now we have the best result with demineralized water in combination with so called Water Wetter from Redline.
No corrosion in the alu parts at all, what is important for the transmission of the heat, and water does cool better than cooling fluid.

The only negative point is that the racing truck where we keep the cars in does need a heating system in winter to keep the frost out.

Hans

[gmsclassics]

Thanks Hans, Porsche radiator fitted and suddenly I have no cooling issues. A weekend's racing in ambient temperatures up to 26 degrees and the water temp only ever got to just above 95 and oil to about 105. That with no overdrive and extended periods at the limit of 7000rpm. A lot of the time the electric fan wasn't even coming on.

Easy to fit and absolutely filling all the available space. Simply had to blank off the hose to the top offside and extend the main two hoses by cutting in two and inserting ali tube of the right diameter. Even has a built in thermoswitch to run the electric fan. Easy.

However I started the weekend with a noisy bearing in the gearbox, lost overdrive on third race, reverse disappeared on race 5 and on race 8 a huge bang changing from first to second off the line and that was that - a 0 speed gearbox!

Now I have to try to work out what else will fit as no more overdrive boxes left. In the meantime I have an old non overdrive box that will probably have to be fitted although I have no idea what condition it is in. Anyone know of a spare gearbox in NZ?

Also managed an excursion in to the tyre barrier at one point - driver error as my foot caught the throttle when braking hard - too fast, over the ripple strip and just couldn't avoid the tyres - no damage fortunately. The jinx of having an in car TV camera for that race. Worse still the TV producer said there was one in the car I had just overtaken so it should make good TV!

Geoff

Geoff

[Hans ten Broeke]

Go for a stag GB a wide ratio gear set and a Volvo J type overdrive, pretty strong together.

Hans