hi,
my comment is not about disapproval but about clarification.

In the XJ forum we call them Lumps when a V8 engine replaces the original 4.2 inline 6.

I know a company who installs 12 cylinder engines in MK2 and S type. I asked them how they do it and they said "very carefully".

 

Thanks Jose. A V12 must be one hell of a tight fit in a MK2 - and I thought I had problems with getting rid of heat - lol !! I'm hoping to post better news regarding my car tomorrow, after fitting the new shroud as
suggested by Jon (fingers crossed).

 

absolutely, a shroud is a no-brainer.

otherwise, heat can be solved Search the forum for member Primaz and his lumped V8 S type. He solved the heat soak problem.

 

Good luck! I have recently fit one of those shrouds. Hopefully it never needs to be removed again.

 

in the S type the shroud is fastened with 4 bolts, one in each corner of the radiator. Not the easiest to fit, but not a monumental job. It just takes patience. The shroud is made of fiberglass, very delicate, but if it cracks, you fix it with fiberglass strips and resin.

 

Thank you both for your comments about the shroud - it took me 6 hours in the end to fit it !! Main problem was that the brake servo (aftermarket one) protruded further into the engine bay than the origional, which necessitated using a Dremel to file an indent in the right-hand side. Also the lower edge required cutting back where it met the bottom pulley (in addition to elongating the mounting holes). Most of the time was taken up fitting, marking for cutting, removing & cutting & then trial fitting again. There's not a lot of room between the radiator and the water pump/fan, so I removed the fan firstly. It helped in removal/replacement to cut the shroud at the bottom centre. When all done I the used a piece of plastic to join both side (small BA nuts/bolts). PLease see attached photos. I ran out of time in the end so can't yet report as to whether this exercise has cured my overheating problem - should be done tomorrow (fingers crossed).

 

I couldn't get mine to line up at all after a lot of struggling, largely due to the stock brake servo! let alone an aftermarket one. I gave up in the end and started trying to remove it deciding to go with no shroud. Then I couldn't get the thing to come out! During that struggle somehow though it finally slotted into place so I hurriedly attached it!!!!

 

Hi Wearlej,

I know exactly what you mean regarding removal. Mine is now in place (following about 10-12 removal & refittings). I started the car up today, checked the ignition timing (as I removed the dizzy and thermostat housing as well). That went OK but when I tried to adjust the carb mixtures the rearmost one (HD8s) started to leak fuel and the adjusting screw went sloppy. I think the jet diaphragm may have split as, when I removed the dashpot, fuel poured from the jet - so that's my weekend sorted !! Carbs off in the morning and off to David Manners before 1pm with a a new shopping list. Oh, the joys of classic cars - lol !!!!

 

So now when I tell you good folks that fitting a shroud on a MK2 with AC is a Bear! Your comments about fitting one without are appreciated and understood if only at 60% or the task of an AC equipped car!

 

Just been for a test run, after which I left engine running on drive for about fifteen minutes. Stayed within the centre of gauge during latter and just below 'NORMAL' during drive, so the shroud has certainly made a
difference. I did get some overflow after standing but, when coooled down, I checked coolant level and it was just visible above the core - so I guess what came out was expansion. I haven't altered my antifreeze mix yet (it's
still around 50:50) so I'm going to dilute that to 70:30 which may help and I'm also going to fit an overflow tank and an electric 'pusher' fan in front of radiator. Trouble with antifreeze it tends to stain the tarmac drive, so I'd
like to avoid any overflow if possible (plus I don't want passers-by telling me I've got a water leak all the time !). Thank you everyone for your input, suggestions and observations - it's appreciated. Incidently, the carb problem I
reported yesterday turned out to be a sticking needle jet - that's now been sorted (thankfully, without removing the carbs).

 

Latest update: Having changed the antifreeze for a 70:30 mix (Water:A/freeze) and changing the thermostat for the 74 degree one the problem appears solved - took it for a good run and the needle stayed at the bottom portion of 'Normal'. Left it standing on drive for fifteen minutes and, although it rose to the top portion of 'Normal' there was no overflow of coolant - Success at last !! Just to be on the safe side I have ordered a 16" electric fan to fit in front of the radiator - Just in case. As an aside, I must admit to being a little disappointed with the acceleration of the car, seing as it's a 4.2 litre (my other car is a V8 XJR mind you so I just put it down to me expecting too
much). Anyway, originally I fitted UM needles in the HD8 carbs, as these were the ones fitted to the 420 and Series 1 XJ cars. By chance I came across someone on another forum who had also fitted a 4.2 engine into his
3.8 E Type together with HD8's and pancake filters (as I have). He was also disappointed with the acceleration and was advised that the pancake filters would necessitate richer needles. I had a pair of UO needles in my box
of bits and so tried those - WHAT A DIFFERENCE - the car literally flies ! Another job done today was the fitting of a small electronic piezo buzzer wired into the indicator circuit, as I found the flasher unit far too quiet and was tending to leave the indicators on. It was a bit too loud however, so I encapsulated it in foam and fitted it behind the drivers instrument panel. It's little jobs like this that, while not original, make driving in modern traffic more
enjoyable. Thanks everyone.

 

I have used 60/40 and 70/30 coolant mix in all my cars since the 1980s. Never a problem. I mean, what is COOLANT for? 50/50 is too much water. Water means rust. The less water the better.

as to the 4.2 acceleration, I have found my 3.8 S type to be more agressive during acceleration than my 4.2 XJ6.

 

CaptainQ has gone higher water less antifreeze. The cooling capacity of antifreeze is significantly less than water, 70% water / 30% antifreeze will run cooler than 50/50 mix. Good quality antifreeze at 30% will stop corrosion as long as it is changed at correct intervals, roughly speaking 2 years for blue and 5 years for pink, the anti corrosion elements in antifreeze deplete over time, proper changes of antifreeze are often overlooked by many. Colour is not always decisive, always check the manufacturers specs as some antifreezes are better than others.

I posted some info on this thread regarding the cooling capacity of water/antifreeze mixes if you fancy some bedtime reading.

 

CaptainQ, the radiator should only be filled to the top of the tubes, the rest of the space should be left for expansion, filling the rad to the brim will usually lead to coolant dump with a 4 or 7 lb cap, if you do the physics/maths, you will soon see that if the volume cannot change (no air in rad) with normal operating temps, the pressure would rise close to dumping pressure.

I started trying to explain the maths behind this but actually bored myself, so deleted it !!!

 

TilleyJon I just love the bluegreen color of antifreeze, can't get enough of it!

I will send you the info you need next few days, many thanks.

 

Actually ethylene glycol anti-freeze is DENSER than water and cools more efficiently. They tried 100% glycol in Rolls-Royce Merlins for the Spitfires in the hope that they could reduce radiator size and drag. Unfortunately 100% glycol leaks like crazy and is flammable!.
You should never use methanol based anti-freeze as it cools LESS efficiently and can cause corrosion.

 

From an oilco man. Mono ethylene glycol is not as good a heat transfer medium as H20 ~ at least 7 to 10% less efficient in thermal conductivity.

 

Ah Yes you are right Glyn. I had misunderstood why early Merlin engines ran 100% glycol. Glycol has a specific heat of less than 1

 

``` Duplicated somehow.

 

As I recall, the only advantage of pure glycol as a coolant is its boiling point, something like 190C at atmospheric pressure. In a high performance piston aero-engine, this allows a low pressure, high temperature cooling system with small radiators and no localised boiling. Curtiss-Wright used pure glycol several years before R-R. I think that R-R eventually settled for what was probably the better compromise of pressurising a water-glycol mix. My feeling is that also applies for our old cars today.