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Cooling Upgrade

Hey Everyone,
I think its due to upgrade my cooling system for the hot 202. Ive got a new 3 core v8 radiator but want to get rid of the belt driven fan which does restrict some power and revs. So that calls for a thermo fan but im not sure what size to get? or to get one at all? I was looking at maybe a 14 inch davies craig thermo fan but on the weekend i saw a sweet 202 only running a v8 radiator (no fan at all). So i was wondering what you guys would recommend? and if there will be any issues with installing a thermo fan?
Thanks in Advance

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Cooling recommendations

I recommend a 16" fan if it will fit or 2x12" fans if it will not, I also recommend using them inside and outside if possible and finally as ever I recommend using an ewp, I'm sure I sound like a broken record about ewps by now, there is plenty of info on cooling in the Holdenpedia, link is up the top right.

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202 cooling

If you have a large chev style V8 radiator attached to a 6cyl, like i have, you wont need much extra coling.

driving along my thermo's never come on unless im fully stationary for 10 mins or more.

a single 16" thermo should be more than adequate for any hot 202.
i run twin 12" thermo's.

Nissan Skyline - Car for the Playstation Generation.

Electric fan / clutch fan.

I have a clutch-fan on mine. The kind that has a sort of viscous coupling so the fan runs full speed at idle when the car is stationary, but slips a whole lot when the car is above 40 k's or so. The fan then slows down to about 1000 rpm. I thought about an electric one for along time but I decided a clutch type one was more reliable. It is a whopping big 7(?) blade windmill. If you get one, get the shroud that goes around it too.

There are two types of these fans - one has a small spiral spring about the size of a 20c piece in the front centre, the other doesn't. The spring when it gets hot unwinds a bit and progressively locks up the coupling so the fan runs full blast if necessary on a very hot day. You sure can hear and feel it!

The no-spring type is what I have and is still pretty good but if you do towing etc I'd recommend the spring type. I have had electric fans in the past on other cars.

clutch fan

I agree with circlotron, I always prefer to have the viscous coupling fan on my engines. Definately get a fan shroud, I believe your holden dealer still sells them new, a mate who works at one bought a brand new one late last year, with out the shroud the fan doesn't do much.

Cheers, Lyndon.

Technology: The more people don't understand it, the more they crave it.
The Shed of SSwampy
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chop chop

this reminds me when l put a v8 into my first car , and used this big fan off somthing...anyway my dads mate came to look at the holley for me and he leant over the fan while motor was running.well his shirt got ripped off and scarred the [Naughty Pottyword] out off dad cracked em....looking back..what a pisser

Thermo Fans

The above is good advice, but there is a better option.

Either EL or AU Falcoon twin thermo fans which come in their own, easily modified, shroud. If they can keep a 300-odd HP Falcoon cool, they'll be fine on your 202. Just get a radiator mob to put a switch housing in your top radiator tank and wire them up through a relay.

VT - VZ Gen3 fans are similar and just as good, but a bit thicker, I think. Use them if you don't have clearance problems between radiator and motor.

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Best fitted to bottom hose

Best fitted to bottom hose (despite Davis Craig doco). You want the fans to kick in when the radiator is not doing its job (slow running/stopped/hot day etc).

The water temp leaving the engine is more or less constant, within say 10-20 degrees. The temp leaving the rad (entering motor, front cylinders) varies from engine temp (no colling to speak of) down to really low temps when cruising on a cold day, like 30-40 degrees! Set thermo to kick in around 50-60 c.

This is from lots of testing and experience!

Bypass radiator when cold

I read something about this particular thermostat setup a while back and the idea was that a thermostat instead of simply letting more or less water flow through the radiator depending on the temperature like usual, was a water diverting device so that when the engine is cold all the water exiting the head goes full bore back into the pump inlet. As the motor warms up a greater proportion of the water is allowed to go through the radiator and when cooled gets mixed with hot water from the head *before* going back to the pump inlet and then block.

Knobnose is dead right about stone cold water hitting the front cyls when the air temp is cold and the motor is not working hard. It would wear more and/or the hotter rear cyls would be more likely to ping first.

Some engines like that 32 valve Lotus V8 optionally fitted to some Corvettes has the water going backwards. A cooler head allows higher compression ratios on dud fuel before pinging starts and also pre-warms the water befor it gets to the cylinders.

Holden -> good. Ford -> bad.

Well, the other prob with

Well, the other prob with uneven cylinder temps is the variation of ignition timing between cylinders!

The system I use is called Ecotherm, produced by David Bennett of Ecotrans, Airport West Melbourne. Did you know that a few Jap engines run this bypass type system ex factory?

It's all about regulating engine temps, not exit flow rate based on exit temps. Works a treat, engine warms quickly and never boils. Of course the other secret is a perfectly operating overflow system that maintains adequate operating pressure within the system, thus elevating the boiling point of water.

Been running an Ecotherm for 10 years now with one of John's modified pumps. He replaces the impellor to close up clearances, increase flow rate and minimise cavitation. As I have said many times before, its the lots a small things adding up that make the difference.

I would not put one of the electric pumps on in a fit! Especially the way the manufacturer recommends setting them up witht he sender unit in the top hose! Pointless!

Look at any closed loop temperature control system, the reference point is critical.


i have a heavily worked 202 in my eh and removed the belt driven fan to fit a romac balancer, im running a 16inch thermo from aussie desert coolers and it does a great job and wasnt real expensive either. give em a call and have a chat with norm

Hey Thanks to everyone who

Thanks to everyone who has given me some advice on this topic very helpfull indeed. But what prices am i looking at for say a 16 inch thermo. I know the 12 inchs are about $180 but i dont want to spend too much over $250 - $300
cheers all

thermo prices

12" fans shouldn't cost you any more than around $100-$110, there is usually not much difference in the price of a 12" and 10" fan, I can't remember what my 16" thermo cost sorry but it was under $200 (it was cheaper than 2x12" fans) the extra cost will be in getting a thermo switch, but remember one switch will run two fans (I wired mine to power all 3).

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Thanks all especially

Thanks all especially reaperhr. I looked at your work guide for your thermo installation which has given me some pointers for the upgrade even though its a totally different car. Makes me want to get my own shed up and running to help others ond show off my beast lol :) cheers all


No worries sleakvh I'm glad it was of some assistance.

Even with modifying the 16" fan, the fans/ewp/turbo timer have really helped my car heaps, temperature is always in a tight range and that seems to be giving me excellent economy (my last highway run netted me 26.5 mpg at mostly 120km/h with a powerglide auto, a car fully loaded since we were coming back from holidays and a 3.36 diff ratio). If you aren't scared of electronics like some people are with the old cars then there is plenty of equipment available to help cool her and make her run more efficiently.

I know some people tend to rubbish the Davies, Craig equipment but I have not had a single problem with anything I have bought from them, and their service was second to none (and was infact far beyond most companies I have dealt with when doing the work guides). As well as that where the EWPs are concerned they are now in the third generation whereas mine is a second generation item and from what I've read of negative comments about them recently many people are referring to first generation items. Mine has been absolutely perfect and if I had the money I wouldn't hesitate to put one on the wifes car tomorrow along with new thermatic fans.

Good luck with whatever you decide to do but my recommendation is to not do it by halves unless that is all you can afford to do. A thermatic fan is a good first step upgrade, 2 will cool it faster but an ewp will make the whole setup 100% more effective. No matter what people say I've run mine for quite a while now and it still brings a smile to my face when I see how effectively my setup is keeping my engine temperatures controlled.

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Take a look at the flow rate

Take a look at the flow rate of Davis Craig fans. The 16" outflows 2 x 12" by a mile.

I have running a 16" on the inside of my rad for 10 years, never boils even on 42c days in traffic jams. I am surprised the motor has not died yet, 10 years is a long service at those temps. I estimate approx 200,000km of service and still going strong. Famous last words lol!

Cooling upgrade don't forget

Cooling upgrade don't forget to fit a relay between the senser and the fans the fans draw a lot of power when kicking in and can burn out a switch really quickly or weld the points together making the fans run continuosly and flatten the battery.


Radiator blind

All this talk about water inlet and outlet temps has got me thinking. Especially the part about the wide variabilty of the water temp from the radiator back to the block. Anyway, with my car it always runs a bit smoother on a hot day than a cold one and I could never figure out why because the water temp according to the gauge is only a couple of degrees different so not enough to affect anything. Then I got to thinking about the cooled water returning to the cylinder block. If the outside air temp changes by say 30 degrees from one day to the next then this water temp will probably change by nearly the same amount! That would definitely give the motor something to think about... Edit:- on a cold day the thermostat would be open less so the water takes a slower trip through the radiator & gets cooled even more. Possibly radiator water exit temp would vary *more* than air temp? Finish edit.

Something I have been thinking about for years but been too lazy to do is to ditch the thermostat entirely and regulate water temp by using a movable blind in front of the radiator that controls the amount of air flowing through it. Electronics is no problem but the mechanical details are too scary for me :-( Anyway, one benefit would be at normal operating temp, particularly on a cold day there would be unrestricted gobs of cooled but still hottish water swirling into the block instead of a trickle of stone cold water like in a conventional setup. That would have to be better for all sorts of things including more uniform cylinder temps. I'll really have to get around to doing something. High fuel prices might finally get me moving.

Holden -> good. Ford -> bad.

Now your thinking. As well

Now your thinking.

As well as the Ecotherm, I currently have half my radiator covered, the half not forced by the 16" Davis Craig fan. I have to do this with 5c night air this time of year!

I have one of those laser guided Infra Red thermometers, its a must to diagnose and tune cooling systems. For example, I was running a 82c (180f) thermostat in the bottom hose, reading 85c water into the pump/block, leaving the motor at around 108c! Thats 26c rise throught the motor.

Tried a 77c (170f) thermostat and engine exit temp is now around 96c! A 19c differential! Much better! Not only that, I have the headroom needed for summer. Anything over 100c will fail as soon as the smallest leak occurs and pressure is not maintained long term due to boiling in the heads. Amazing how a small tweak like that thermostat change altered things.

For the record, I tried a 160f thermostat also (72c) and the change was noticable, didn't idle or cruise as well, the heater was not quite hot enough for these chilly winters nights either. 170f is deffinately the go for this motor using Ecotherm system.

Oh BTW, even with half the radiator covered, I just measured radiator exit tank temp after comming home at midnight on a really cold night (10c?) and the tank reads 42c - if that was hitting my front cyliders I can tell you wear would be greatly increased! I have a theory that this system is also the reason I have not warped a 308 head ever in 10 years! They can be bad for that, especially rear of even bank. Apparently 308'x are not great in distributing water throught the block, more flow to the odd bank (due to the way the pump works). My modded pump has a small "dam" welded in to balance flow to the block. Another small tweak that helps to acheive even cylinder temps aiding fine tune and excellent performance/econemy.

dnar out.

Oh BTW, with a conventional

Oh BTW, with a conventional system on a cold day you have really cold water entering the block, cooler water leaving the heads so the thermostat should close down to compensate yet yes the water leaving the cool radiator does enter the block and that is not good! Will run more like a cold engine because it is!!!

I have heard the RB30 motors use a similar bypass system but I have not taken a close look to confirm this. Maybe Qute can confirm (or is his a RB20?).

Cool RB

Dunno DNAR...I have 3 RB30's sitting at home but I'm back in Melbourne. I can have a look when I get home in 3 week's time...

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Ya gotta be hot to be real cool

Hi dnar! Been hoping you would show up :0) Read some of your other posts and about your bowl of spaghetti inlet manifold and though 'this guy's on the ball'. For a temp sensor I have this home made thingo using a big copper cable lug under one of the thermostat housing bolts and the hollow part of the lug where the cable would normally go has an LM35 inside and is filled with araldite. 80 deg C reads 800mV. On a 40 deg day at 100kph it sits on 93 deg. with 15 deg air temp at 100kph reads 72-73 deg. I should somehow put one on the return water supply and also ambient air to get some hard figures for various situations.

How did you put a thermostat in the bottom hose? I once had a Peugeot 404 and the thermostat was halfway along the top hose. Looked like a snake that had swallowed something big.

Wow, no issues with the LM75

Wow, no issues with the LM75 sensor? Did you epoxy the 3 legs as well? Photos would be cool if you have them.

My thermostat is in the bottom hose by using the Ecotherm system (as per my posts above under a different name).

If your interested, I can send you photos, literature etc. Ecotherms are hard to get out of John Bennett these days, a mate here in perth bought the CNC design from him and now manufactures them locally in perth. Around $300 for the kit: bottom hose housing, top hose flow director, hose clamps, hoses etc.

John from CHoice radiators in perth also made his own copy, although having seen one I spotted a few design ommissions that I know John Bennett would shake his head at.



Gday Dnar,

I would be very interested in looking at soime literature and photos on these mysterious Ecotherm gizmos. They sound very interesting.

All this talk of covering parts of the radiator makes me think back to when I was riding my RD250LC... no thermostat in them, so I used the side out of an oil bottle taped over (most of) the radiator, with a couple of small holes to allow some airflow. This allowed the poor little 2-stroke to warm up on those cold Tassie mornings. Without at least half the radiator covered the thing would not warm up at all.

Ahh the joys of riding a bike when it is -5c outside... brrrrr...


There is a very fine line between "hobby" and "mental illness".

ecotherm system

G'day I know that the original post was awhile ago.Does your mate still on the off chance still make the ecotherm systems?
My e-mail is

Water temp control

Been giving this a whole lot more thought. Now I am thinking for an adjustable radiator blind, the second best way to control it would be to regulate it's position based on outside air temp; the hotter the air the more you want to let through. The best way perhaps would be to regulate it's position based on the radiator outlet temp which is a function of air temp, air speed and water flow. Leave the thermostat in situ to control the other end of the system.

No doubt I'll change my mind once again...

Yeah, me too. You remember

Yeah, me too. You remember the "venitian" type headlights from 70's Landau's? Perfect me thinks...


Louvre doover

I can only remember the ones on 73 LTDs. I thought they were one piece, but I haven't seen one for yonks.

I also imagined using a louvre window type setup with slats of something replacing the glass. The air pressure would be balanced either side of the pivot points so it would not try to go full open or closed all the time. A holland blind would be pushed against the radiator so it would not slide very well. Maybe a pair of masonite sliders that open like stage curtains. Leave maybe a 150mm gap in the centre.

Run thermo fan backwards

Now this one is just too easy! Have your thermo fan go in the reverse direction just fast enough to oppose the flow of air into the front of the radiator. The area covered by the fan at least could have it's cooling contribution nulled. Fan speed would have to vary with road speed of course.

Sounds too hard. My 16" fan

Sounds too hard. My 16" fan blows [Naughty Pottyword] loads BTW! Would also not work when stationary.

I am thinking how to do a sliding door with roller runners. I have tons of room in front of my rad to do this easily.

At least with the Ecotherm, a really cold radiator is not much of a problem as the thermostat will just stay mostly closed.

One observation I have made is that the water temp leaving the Ecotherm regulating block is around 3c higher than the installed thermostat rating. I am guessing this is because thermostats are rated for cracking/opening temperature, I have confirmed this with a bunch of thermostats, a temp probe and a saucepan of water on the gas hotplate.

Covering the radiator

Today I tried a bit of an experiment. I went and got a piece of shade cloth and covered the radiator with it because it slows down wind quite a bit. Suprisingly it didn't have any noticeable effect. Then I remembered at work I had done some measurements of various airspeeds blowing along the fins of an aluminium heatsink. Going from pure convection to just a tiny whisper of air makes a *huge* difference. Dissipation vs temperature rise improves by about a factor of 4. Going from that tiny whisper to a real gale only improves it to a factor of 6. No wonder my shade cloth had not much effect.

Ok, so lets block off part of the area with a sheet of cardboard. This is not as clear cut as would first appear. If we block off say the top half or the bottom half we won't achieve terribly much because the majority of the cooling happens where the water first meets the air e.g. the water in the very top of the radiator is hot so it looses heat to the air very quickly but the further it goes down the vertical cooling tubes the less the *difference* in temp between the water and the air so the less effective that part of the radiator becomes. You cover up either the top half or the bottom half and the exposed half has hot water waiting to be cooled and that's what happens. The part you covered up wouldn't have contributed very much anyway.

If though we cover up a *full height* section, different story. The heat dumping effectiveness from top to bottom of the radiator is the same as normal but we are only using a percentage of that radiator. That's exactly what we want :-)

I blocked off about 40% of the radiator this way and went for a toddle down South Gippsland Hwy and back at 100kph for about 120km. The air temp was about 21 deg. Normally the thermostat outlet temp would have been 73-74 deg but this time it varied between 85-87 deg. Return water temp going back to the block under these conditions was about 70 deg. I'd pull up quick, bail out and put my finger on the bottom tank. For a 1-second skin contact, 50 deg is warmish, 60 deg is starting to sting, 70 deg is oooh!, 80 deg is yow! It was oooh! The oil filter felt way warmer than usual too and the tappets were slightly noisier. One big difference was the tranny was way hotter courtesy of the fluid cooler going through the bottom of the radiator. Tranny is so-so at the best of times but I would go to move off and would almost have no forward gear in drive. Click it to 2 or 1 and it would move off fine.

Upshot of all this was that Brown beauty ran as smooth as a baby's bum. That was good. Another contributing factor though was that I reduced the cross sectional area of the gas mixer that sits on top of the carb from a 46 mm dia circle to a 14 x 28mm rectangle so for a given air consumption the airspeed through it increases by a factor of 4:1 and also gas/air turbulence beneath this hole increases massively. Lousy for performance but gread for economy & smoothness & emissions. Will detail it when I get my shed going.

Good to see I have a

Good to see I have a beleiver!

Most people spend all their efforts on maximising the cooling of their rad, getting the coldest air into the carb and maximising flow through the manifold and heads.

All well and good for drag racing!

My rad is crossflow, I currently have 50% (drivers side) covered with 3-ply. Ample cooling.

I too have my trans cooler in the outlet tank (factory) so I wet the thermo fan to run and maintain a maximum radiator temp of 55-60c, even this may be too high for the trans but it has not given any problems in years. Fan/rad temp is maintained under 55-60c proviging cool enough water to mix with engine outlet to obtain the desired engine inlet temp of 77-80c.

As for your carb mod for turbulence, excellent. I run one of those Hyclone's just after my LPG carb, makes a small improvement to economy.

Your right, if you can just hold your hand on metal without pain, thats around 50c.

Put your efforts into regulating all aspects of your engine: individual cylinder mixtures, spark, block and head temps etc and you stand to pickup a few percent with each mod, adding up to a marked improvement. Don't settle for any spark scatter! Do you have access to a spark analyser?

Crossflow radiator

With a crossflow radiator I think you would want to have the full width and part of the height blocked, the opposite of a "normal" radiator. The whole thing is basically laying on it's side.

Might have to go for an external trans cooler on the return line to the box.

The carb mods are just the begining! When you put your foot more than halfway down it makes a sound like a water tap being wound through it's swishy range near turnoff. Must be quite plain to hear outside the car. Performance is leisurely - overtaking is not an option. 100 -> 120 kph (on a racetrack of course) takes about 10 seconds and is still going afer that but not much. Under such conditions and assuming 50% volumetric efficiency the airspeed through the mixing orifice is now about 100 metres/sec or 360kph. Yum!

I don't have a spark analyser as such but I do have a conventional lab scope so I use that. I have made several different 2D and 3D spark timing boxes over the years but at the moment I am just using the conventional HEI dissy. One day I will get myself organised enough to put one on again along with a crank trigger.

At the moment I am using 100 thou / 2.5mm plug gaps and that is worth it's weight in gold, but I have to use a 16 volt supply to the ignition module otherwise the car just won't start because the battery voltage drops too low when cranking.

Anyway, the gas mixing and water temp thing is enough for now. Just gotta get those LM35 temp sensors on bottom tank and ambient air. Yes, araldite is not a problem with those things.

100 thou gaps!!! What plugs

100 thou gaps!!! What plugs are you using? You don't have a problem with inductive leakage or crossfiring?

Gaps for chaps

The plugs are just some 6 year old Bosch thingo's with 123,000 km on them. The centre electrode is filed almost flush with the insulator and the side electrode is seriously bent upward. I have managed to keep the surfaces of the spark gap parallel though. Anything beyond that gap and the spark instead jumps sideways from the centre electrode across the surface of the insulator to a point part way up the side electrode.

I really gotta get new plugs and I saw some today that had the centre electrode poking a good 5mm out of the insulator. That would enable me to file it back to the gap I want without bending the side electrode silly. They were resistor plugs and I didn't see any non-resistor ones in that style for a 202. Do you know of any?

just lettin yas know it cost

just lettin yas know it cost me $350 for a 16" davies craig and thermal switch thing not cheap

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