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« on: July 27, 2010, 21:20:21 »
Damien, it's looking very impressive in the photos - congratulations. Is the paint Guardsman Blue? Do remember not to have your head under the bootlid on a windy day - an AC design error in my view to put the lower pivot of the gas strut too near to the line of the hinge pins. On CF6 I moved the pivot pin down and further back and a longer strut holds the lid against a wind and assists the opening of the lid. What are the 'small black handles' on the dash you were looking for?
Re your cooling/air in the water concerns - I assume your header tank is the original or repro Serck rectangular tank mounted so it slopes down to the front and the front pipe stub is in line with the rad stub. You are right that air bubbles circulating in the water are a BAD THING. Air in the water reduces heat transfer in the radiator, may cause local boiling in the very hot parts near the exhaust valves and at high rpm may encourage cavitation in the pump inlet. I reckon the capacity of the header tank is about 4 pints(Imperial) and the expansion of the CF6 system from cold to hot is normally about 2 pints but has been to 2 1/4 ; let's work on 2 1/4 pints. If your header tank were full when hot with no air in the system then when cold it would have drawn in 2 1/4 pints of air. The inlet and outlet pipes will be uncovered and air will go into the circulating system at the next start. So I think your problem is lack of an expansion tank rather than height of tank or hoses. A single header/expansion tank can work but it needs to be bigger and higher than the rectangular Serck and preferably not part of the circulating system.
Apart from CF1 I think all 428's probably have an expansion tank in addition to the Serck header tank. With this setup the header tank has a plain cap sealing on the top lip of the neck, the pipe from the neck to the expansion tank is pressurised and has hose clips and the expansion tank has the 13psi pressure cap. All 428's I have seen have a black painted expansion tank with a distinctive kidney shape taken from BMC 1300 and 1800's of the 60's. I think this was a design error because the tank has a volume of only 2 pints and the feed pipe which goes in from the side stops 1/4 pint from the bottom so it can only cope with up to 1 3/4 pints of expansion without dumping water on the road and/or drawing air back to the header tank on cooling down. I think it can just about work without topping up but the cold levels would be 1/4 pint of water in the bottom of the expansion tank and 1/2 pint of air in the header tank some of which might get circulated. I found this impossible to judge and could never resist the temptation to top up both tanks. In the discussions about 'overheating' I haven't seen any reference to topping up and wonder how much of this other owners do.
I replaced the original expansion tank with a BMW tank which is translucent plastic, designed for 13psi, has a neck which takes the original AC-Delco cap, is a suitable shape and can just cope with 2 1/4 pints of expansion. I mounted it on the RH inner wing panel above the alternator/front end of the rocker cover and have a cold level line on it so I can check this without removing the cap. The header tank is completely full hot and cold. Since 2004, doing 2 or 3 thousand miles a year I have topped up only at the end of the season when it will need about 1/4 pint to restore cold level which I think reflects coolant loss from pushing damp air out and drawing dry air back in.
On the road indicated temperature, depending on ambient air temerature, is 80 to 90C (88 to 93 true).The electric fan switches on/off at 115/102 indicated (103/99 true at the sensor) in slow traffic and idling. The Otter thermoswitch in the header tank for the fan makes at 90 and I have a manual switch in parallel and a 'fan on' warning light so I can switch the fan on before I reach a traffic jam.This all seems to work OK and I think you should not worry about the number the needle points at if no topping up is needed because, by definition, it has not overheated or lost water.
For those still reading this I add a few general points. Discussion of 'overheating' has focussed on water, engine bay and car interior temperatures. On the water temperature issue I think the larger expansion tank is a good start plus: 1. Cure all water leaks - even a small one will lose significant water with hot 13psi water behind it over time.2. Pressure cap valve lift at 13psi is vital to maintain system pressure and is worth checking regularly. At 13psi water boils at about 117C and this is important to maintain a safety margin over water temperature. 3. Fit a big fan. I have a 16" Kenlowe; it pulls 21 amps but shifts 2320 CFM in free air and about 1900 CFM installed - still only about the same as 15mph. The matrix of my radiator is 19.5" wide x 17.25" high x 2.75" deep. Is this a typical size? 4. I think you must have a thermostat to get a fast warmup and reduce engine wear which is dramatically higher at low temperature. I reckon opening at 74C and fully open at 86C is about right in the UK. 5. For most of us who see highest temperatures at idle/low speed an aluminium Edelbrock water pump is worth considering. They claim higher, but unquantified, flow rate at low rpm and I was prepared to believe this having seen the crude 'paddle wheel' impeller in the original Ford pump which also weighs a ton. 6. With a header tank always full there is a case to eliminate it.I think the Cobra Mk1V has a header/expansion tank with a system filler in the pipework at the highest point. I kept my header as it's a convenient place for the Otter fan switch and I thought the internal baffle directing the water flow under the filler neck would capture any air bubbles (inevitable when you have drained the system).
So far as engine bay temperature is concerned I didn't like the fierce heat which hits you when you open the bonnet after a fast run and in years of motoring the 428 is the only car in which I have experienced fuel vapourisation. I think you should have a minimum of fuel pipework in the engine bay and insulate it where you can. I fitted 2 extraction fans to draw air out and through the side vents which seem otherwise to be more decorative than functional.These shift 1200 CFM of air total and lowered the engine bay temperature by about 6C on test with no noticeable effect on water temperature. However this modest reduction takes some of the sting out of the heat and I think has avoided fuel vapourisation which has only happened at idle/low speed. Incidentally I don't understand the aerodynamic theories we have heard and the talk of bonnet louvres. Whilst I would expect louvres to lower engine bay temperature I doubt they would have significant effect on water temperature except perhaps at very high speeds. I wouldn't want to change the lovely lines of the car but if you were to add bonnet louvres I would have thought 1/3 to 1/2 way back from the front end would be a low pressure area to put them whereas the rear end of the bonnet just ahead of the screen is a high pressure area - isn't that why modern cars have their interior heating/ventilating air intakes there? And is there evidence that an Aceca with louvres runs cooler than an Ace without but otherwise the same ahead of the screen?
So far as excessive heat in the interior is concerned I think the solution is don't drive a fastback, do drive a convertible with the soft top down, don't drive in California, don't have an auto, do have good footwell fresh air from the fans at the front end with the ducting going above the front wheels outside the engine bay and, if all else fails, follow Emmanuel's advice on heat insulation to isolate you from that 7 litre space heater!
I hope Damien that you (and others) may find some of this helpful and that it may elicit other/differing views and experiences. The 428 is a super car and I hope you get as much enjoyment and fun out yours as I have from mine.
Michael
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