Cooling for V8 Hunter3.9i

[greyV8pete]

I am still pursuing my hot running saga (see next Pitstop / rich running sequel). I fitted a Kenlowe 13" series 2000 fan some time ago and apart from blowing fuses (now sorted by higher rating slow-blow type) seemed just about enough to cope. Since fitting the Optimax chip and Lambda sensors driveability is dramatically improved and fuel consumption has decreased dramatically, thank goodness! However the trade off is that the weaker mixture causes higher running temperature. It will just hold 85degC on a really cold day if the heater is on first switch click. Any warmer ambient and I need the heater on second switch click. Following slow traffic full heater and Kenlowe on will only just about cope. I fitted a new thermostat as a precaution with no improvement. Rover only list one t-stat / temperature for the 3.9i L/R Disco! No winter / summer / export variants listed!

Have now removed the MOC badge, badge bar and relocated the spot lamps from “standard” location to hang them under the headlights, all in pursuit of getting “clean” air straight into the radiator. Rad is Marlin 3row X-flow type. Currently modifying standard Hunter grille to be "front removable" for instant access, so I can pull the fan forward to stop the motor blocking the core. Addition of rim seal around fan outer diameter to fill the resultant gap and a construction of a Ram Air box to force all the air through the rad core, rather than around the rad, will hopefully stop the fan cutting in during normal driving.

What fan size, make etc do other V8 owners use? Is cooling adequate or marginal? Does anyone else have fuel injection? I have seen a Cabrio and a Berlinetta in the past with an additional radiator underneath the front. Is this in the main coolant circuit or in the heater return circuit? If in the main coolant circuit does the standard water pump / pulley size give adequate circulation? Some advocate replacing standard rad with an Aluminium one. Very pricey! I still favour the extra rad as it would further add to the coolant capacity and slow down the temp gauge needle! All ideas / comments welcome. Peter.

[dogoncrazy]

Re: Cooling for V8 Hunter3.9i

Peter
Rimmer bros. list three different thermostats for V8 engine , 74/82/88 degree if that helps.Take a look under their V8 engine on line catalogue

[h_m_cumming]

Re: Cooling for V8 Hunter3.9i

Peter, have you actually checked your t/stat is opening fully at the marked temp.? I've also found that putting the fan behind the rad seems to give a better effect than in front although not every installation will allow this. As you say, making sure all the air goes through the rad and not round it is the main thing.

[h_m_cumming]

Re: Cooling for V8 Hunter3.9i

Just a further thought, if you take the stat. out does it still eventually run hot?

[greyV8pete]

Re: Cooling for V8 Hunter3.9i

Thanks Alan. Can’t remember what temp mine is. Will check the box if I can find it. It’s got the old stat in it so I can check that one too. I am sure that they were the same temp anyway.

Thanks Hugh. I haven’t taken the stat out completely but both the original and the replacement stats gave the same symptoms so assume they are both working ok.

On anything but very cold ambient, without the heater fan blowing hot air up the windscreen the temp will just keep creping up until the Kenlowe cuts in. Even that is hard pushed to cope without the heater in traffic. It all points to lack of “effective” cooling area / coolant volume to me. The Marlin rad is only 40% of the area of a RR rad and the Kenlowe motor blocks a load more of the effective core. Hence the current mods ;-).

I would love to put the fan behind the rad but my engine has the serpentine drive belt so space is pretty limited, even for a Marlin! Also would mean cost of buying a new fan as the series 2000 Kenlowe has curved / unidirectional blades. The Hunter grille is made from ½” wide strips of dural welded to same size X braces so it uses up 1” total space front-to-back. May consider gaining this space by fitting a Cabrio type wire mesh grille, as fixing an overheating engine is more important to me than aesthetics.

Further thought. I know that incorrectly advancing / retarding the ignition timing can have a considerable effect on running temperatures but can’t remember which is worse? The instructions with the Optimax chip recommend a basic static ignition timing of 8deg BTDC so mine is set to that (the book setting is 6deg BTDC). RPI engineering say to drive it in top gear up a gentle hill and floor the throttle. Keep advancing the dizzy until it just starts pinking then back it off to the previous position. I haven’t tried this yet. Some books say that in a light car some of these V8 engines need to run at 15deg BTDC static! Peter.

[h_m_cumming]

Re: Cooling for V8 Hunter3.9i

The advice about full throttle on load is correct at low revs. but not so reliable as the revs climb. What is the CR Peter?

[greyV8pete]

Re: Cooling for V8 Hunter3.9i

All noted Hugh. CR is 9.35.1 which is standard for the HC version acccording to the Haynes workshop manual for the L/R Disco. Engine originally fitted new by Marlin Cars at POB. Has done about 25k miles only. Peter.

[h_m_cumming]

Re: Cooling for V8 Hunter3.9i

Another thought, I'm having a few tonight, is the system pressurising? If it's not that will lead to overheating.

[h_m_cumming]

Re: Cooling for V8 Hunter3.9i

Here's another. You don't have a head gasket going and blowing into the coolant?
I'll go now before you have a heart attack. Best of luck.

[danny_nelson]

Re: Cooling for V8 Hunter3.9i


Hi Peter , the rads you have seen under the front apron are
probably oil coolers. I have had several V8 engine Marlins over the years and I have found that an oil cooler is a must
also as large a header tank as you can make room to fit, to help increase the coolant capacity. I also run a greater percentage of antifreeze, and I know a member who has added
wetter than wet and had some success. My present header tank adds over 2ltr to my system.
Regards
Danny.

[h_m_cumming]

Re: Cooling for V8 Hunter3.9i

To add to Dannys reply, here's a pic of my oil cooler which sits under my rad.

[greyV8pete]

Re: Cooling for V8 Hunter3.9i

Hugh / Danny. Many thanks for the feedback. My system is pressurising as I fitted a replacement filler cap and pressure cap since I had the car. Danny is your header tank on top of the rad or remote? As I have the X-flow rad the tanks are at each side. There is a T off the main hose filler with a single 6mm pipe to an expansion bottle on the bulkhead but that won’t really contribute to cooling as it’s not in the coolant flow circuit. Also I have a bulk tank in the heater line, fitted by Marlin at POB, apparently to increase capacity / heat soak.

I have added water wetter but saw no improvement. One rad that I saw under the front was definitely coolant as the pipes were water not oil. It was at Colerne track day maybe 3 years ago but I can’t remember the owner’s name? He was from Lancashire I believe?

Hugh. Thanks for the photo of the oil cooler. Mine has about half the height / no of rows of yours! It is also half hidden behind the steering rack which won’t help much!

Interesting that you mention the head gasket. I have been hoping that train of thought would go away ever since I read about it on the RPI website regarding standard RR chipping for a 2 ton vehicle being totally unsuitable for a 15cwt kit car. See link below.

http://www.v8engines.com/carbs-Morganhotwire.htm

Re my alloy rad idea. Radtec do a replacement for a Caterham V8. See link
http://www.radtec.co.uk/index.php?p0=detail&id=228&cpid=26&cid =56&partNo=RC7%20E

Not sure what size it is? The nose of a Caterham is pretty small so maybe it would fit in a Cabrio. Please keep the ideas coming. Target completion date is before the Winter Shindig! Peter.

[copperleaves11]

Re: Cooling for V8 Hunter3.9i

Hi Peter. When I first built my Sportster, overheating was foremost in my mind especially as I have used Marlins three row rad and I thought it would not adequate. My engine by the way is only 3.5L(piper 270 cam, weber carb, stainless exhaust manifolds). The cooling fan, so I was informed was new but originally intended for an air-con unit came fitted with a four blade pusher fan, which I subsequently changed for a five blade puller of the same diameter(12inch).The thermostat is an 88deg, the sender for the fan is fitted in the top hose and the airflow is ducted up through the rad and the manifolds are lagged. The end result: the fan does not cut in unless stationary, or below 15/20mph on a hot day and even then only needs a couple of minutes running to bring the guage temp. down to the normal 89/90 deg. I have only got an ex mini heater(single speed fan) through which the coolant flows continually and have never needed to use it to control the coolant temp. The only other point which may be relevant is that when building the car, I opted for a lot of louvres on the upper bonnet halves(which I curse every time I clean the car) to help reduce engine bay temp. The photos may help illustrate my babbling. I hope this is of some help. Regards.

[copperleaves11]

Re: Cooling for V8 Hunter3.9i

Sorry photos were too large.

[danny_nelson]

Re: Cooling for V8 Hunter3.9i

Peter my header is remote, and the car that you refer to was either John Mulvaneys or Dave Kitsons as they were both there with V8 powered cars.
Regards
Danny.