Hmmmmmm.

The things that spring to mind are:

A larger rad to start with

Bigger or twin fans, perhaps a manually operated extra fan

Alloy panels /ducts out of sight to channel air to where its needed

If the temperature rises like you describe, it would seem that the rad can't cope and it needs a bigger one?

Those would be some of the options I would consider, stood in your shoes.

Overheating at speed
 

I've had another think about this, and something does not seem quite right here.
Usually, the faster you go the more air passes through the rad and the water temperature should fall, not rise. But in your case it doesn't.

Therefore logically something is wrong. But what?

Back to basics:

Buggered water pump, thermostat not functioning correctly, restriction point somewhere in the system, perhaps it is a simple, easily cured fault Mr Towed.
Perhaps someone reading this can offer some advice?

Come on you guys!

Just reading the pass few post and I think you should look at the "air flow" first.
Formula 1 teams found at speed a scoop creates cavitation around the edges and slow down or at least restricts the air flow.
I think at 70MPH the air is not all passing through but getting trapped and being buffeted around the engine bay keeping the heat in and over a period of time building up and blocking or slowing down the flow of external cold air.

I have known of a simple mess grill causing similar cavitation problems.

Are you using inner wings? If you are not try fitting them, if you are try removing them or cutting some vents in them.

As Scottie22 said higher speed should mean greater air flow and cooler running.:plane:

Hope this makes sense :icon_confused:

Mr Towed,
I have run your situation past my friend who is very well versed in this sort of thing, and what he said was: take the thermostat out and go for a fast high speed run, if the temp does not fall, he thinks you may have a head gasket problem.
This test at least would rule out the thermostat as the fault.

Guys, this is a well known issue with the donor cars (Spitfire / GT6) The issue is not getting air into the radiator, but getting the hot air out of the engine bay. In most conditions, this is not a problem, but in high speed running it does cause problems. That's why the Le Mans Spitfires had extra bonnet vents behind the front wheels, and the GT6 has extra louvres on top of the bonnet.

Towed, with your large scoop pushing extra air into the engine bay behind the radiator, it is not surprising that you have reduced airflow through the matrix...

Extra radiators and pumps will not help in this case

Baz from Brusels

Electric thermostatic fan blowing air OUT of the engine bay?

[edit]
Just looked back at pictures of your engine bay and bonnet and there are no convenient vents. Perhaps you could vent it out of the wheel arches?

I seem to remember the original Minilites were designed to suck air across the brakes. I am guessing sucking warn air across the brakes is not ideal so perhaps some flexi ducts (http://www.i-sells.co.uk/ducting-flexible-hoses) positioned at the top of the arch out of sight?

The supplementary cooling system will have to wait for another day now as it's not an urgent upgrade, just one that I want to make before I undertake any more motorway journeys, which won't be for a while now.

Another non-essential change took priority today as I had a pair of 175/80/14 tyres fitted this morning to replace two of the 175/70/14's I've been running.

You can clearly see the difference in diameter, the new size is on the left -

http://i1301.photobucket.com/albums/...psfd84842c.jpg

The reason for only ordering two is that I wasn't sure they'd fit on the front without further modification to the bulkhead, but I was confident that they'd fit on the back, so I could always run with the lower profile tyres on the front if I couldn't make the bigger ones fit.

To my surprise, they fitted on the front with no more fouling of the bulkhead than the 175/70/14's exhibited before I raised the front suspension. They just skim the bulkhead on full lock, but it doesn't restrict the steering or cause any judder. I took it for a test run for a couple of miles and threw it round a couple of roundabouts with no problems.

Here they are fitted to the front -

http://i1301.photobucket.com/albums/...ps70944452.jpg

I then swapped them to the back as it looked a bit odd running with smaller tyres on the back than the front, and went for another test drive. Guess what, they fouled the rear arches during the roundabout test :(

You can see how little clearance they had here -

http://i1301.photobucket.com/albums/...pscac4c80d.jpg

So, it was out with the rear spring, again, so I could remove the final 18mm of lowering 'shims' and put two of the recently removed intermediate springs back in for a slightly firmer back end (ooh, Matron!).

Before -

http://i1301.photobucket.com/albums/...ps3a8f652c.jpg

After -

http://i1301.photobucket.com/albums/...psccc96521.jpg

And as Goldilocks would confirm the result is just right -

http://i1301.photobucket.com/albums/...psb4a16264.jpg

http://i1301.photobucket.com/albums/...psd41b5ecf.jpg

They don't foul any more and I've actually got some ground clearance. The taller side walls are more compliant and compensate for stiffening the rear spring while I'm pleased with the way they look, so I'll be ordering another pair for the front.

Mr T, I think the wheel/tyres and suspension is one of the greatest arts with these cars. :icon_confused:


Yours is looking good now and probably will sit at the same height as Phil's two. My Miglia will have no lowering at the back and 70mm off the springs at the front so should sit about where yours is now.

All part of the fun of ownership though! :icon_razz:

Cheers Tony, are you going with fifteen inch wires again or something different for your Miglia?

Yep 15" wires with 185/65 tyres.

They are a little chunkier than the standard wheel/tyres...


http://www.mymigliaspeedster.co.uk/images/wheels.jpg

Initial try with the body looks ok

http://www.mymigliaspeedster.co.uk/b...0arrives/1.jpg

I need to trim the wheel arches - in fact I have started but a holiday and new kitchen for a friend got in the way!

I haven't lowered the back at all and when it has all the seats and interior, fuel tank etc it will settle a bit anyway so should be okay.

Hope to get on and do a bit more over the next few months if the weather stays okay.:eusa_whistle:

Have to say i agree withe earlier post T, the scoop on the bonnet is allowing air in and equalising the pressure in the engine bay against the air coming in the front of the bonnet, the result is a stagnant area in the engine leading to lack of flow through the rad, had this issue on one of our race cars some years ago, some good size vent holes on the sides of the bonnets should help or possibly block off some of the front of the scoop? We solved the problem by fitting a flat floor, rear diffuser and sone fancy ducting, might not be appropriate for you though :-)
Nice upgrade on the tyres BTW, you must be getting expert at "whipping your spring out"!!!
Mac

Hi Mac, spring out in under thirty minutes, a new personal best!

Spring back in in three hours, what a pain in the ar$e!

I agree about the scoop equalising the pressure in the engine bay. I don't want to block off the scoop or cut vents in the sides. The plan (now) is to plumb in the rear mounted radiator with an electric pump, and, now I have some ground clearance, put a chin spoiler type arrangement under it to scoop air in at higher speeds. Might even give me some downforce on the back tyres, very Fomula One.

Nice wires Tony, new chromes by any chance? You might want to take a leaf or two out of the rear spring to get the ride height right. I'm becoming a bit of an expert on changing the small chassis Triumph suspension now. :peace:

Don't want to be negative, but if the issue is indeed the lack of airflow through the engine bay (ie air in AND air out), a chin spoiler will not work...
It would be just like trying to force more water into a bottle that is already full.

Baz from Brussels

PS: the new tyres look fantastic!

some venting like this?

[IMG]http://i1330.photobucket.com/albums/...psa8e73343.jpg[/IMG]

Won't that end up in the cockpit?

Don't worry Baz, any advice is always gratefully taken on board.

I did wonder if I'd explained myself properly with the 'chin' spoiler idea. It's not going on the front but under the rear radiator to ram air into it at speed. I might even engineer a motorised or mechanical flap that lowers into the airstream dependant on speed and/or temperature, a bit like the engine cover on a 90's 911.

That way I'm hoping that the second rad won't over cool the engine in day to day dawdle driving, but will kick in at motorway speeds and stop the temperature rising too high. And because it will be between the back wheels it won't ground going over speed bumps.

As for bonnet vents, if you remember I actually have louvres at the back of the bonnet, but they're blanked off dummies at the moment. I could always grind out the remaining fibreglass behind them I suppose...

http://i1186.photobucket.com/albums/...ion/002-73.jpg

Nice to see your car coming together Christine, it's looking very nice indeed. How long before you hope to be on the road?

Mister Towed, I think opening those louvres is the best idea yet and will
go a long way to solving your problems.
The D Types had them and had no probs at 170 mph at Le Mans!!

On top of the obvious cooling advantages, letting the air out of the bonnet void will reduce the tendency for the rear lip of the bonnet to 'pant' at speed.

Hope not, it would certainly start a draft :whistle:

Just kidding. I won't block up the space between the bulkhead sides and body sides. Theoretically you don't need vents if the air can flow thru to the rear wheels. I'm not sure if plywood builds would benefit from this (venting/drying the wood and prohibit condensation) or ruining it (because of mud, dirt, spash/spray).
I'm using stainless steel and coated aluminium which should handle a variarity of conditions.

Michiel

I have watched with interest when you fella’s fit oversize wheels and tyres, and the result Is always an improvement on the original. They fill the arches and look good.

But one thing puzzles me, what do you do, to compensate for the extra rolling diameter?

The speedo must be out, and, to some extent the gearing, and if the wheel is quite a lot larger, The acceleration must be ruined.

Do you re-calibrate the speedo, or use a satellite driven one?
Do you change the gearbox ratios or back axle?

The most extreme example I can think of recently was Patoune on his D Type, he fitted 185 x 100 x 13 tyres, which would result in a whopping 21 % + increase in rolling diameter.

The acceleration must have been snail-like in the extreme!
No pun intended!
I understand he races them, so I guess he must have swapped the gearbox or back axle, or both.

If you’re reading this Patoune, please, what mods did you make, I’m really interested?