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MG MGB GT V8 Factory Originals Technical - Thermostat and 'in tank' swirl pots question

It's alive! ah ha ha ha !! (Dr. Frankenstein type mad laughter)

Yesterday I got my 3.9 EFI V8 conversion started for the first time, how ever there were a couple of glitches (as there always is I expect).

I have used the Rover temperature sensor, simply attached the MGB temperature sensor wire to it.
This then showed that the thermostat on the V8 is opening at three quarters of the way up the temperature gauge, which I suspect can't be right as the thermostats on the Rover and MGB (1975) should both open around 80 degrees C. I had assummed that the MG and Rover temperature sensors sent the same signal. I suspect that this isn't so and I need to substitute the MG temperature sensor for the Rover. Can anyone confirm this?. Or maybe I can adjust the temperature gauge? (resister?)
Further to this, I am using a very large electric Fan which (via a relay) I am controlling with the Air conditioning temperature switch. The 3.9 motor I have is a RangeRover motor and it has the Air conditioning fan temperature switch in the mechanical main thermostat housing..This switch doesn't cut in until the MG temperature gauge is in the "H" for Hot section however since this thermostat has 94 deg C stamped on it I'm inclined to believe that this is further evidence that the temperature Sensor/gauge combination isn't right. However 94 deg. seem a bit high anyway so can you get a switch for around 85-90 deg C? , What did they use on the RV8 which has the same thermostat housing? I know you can get adjustable temperature switches (which locate in the radiator), however it seems a pity not to use the existing location.

The other question concerns fuel supply. I am going to buy a new petrol tank and have a swirl pot (antisurge baffle) welded in. I've never seen a swirl pot , but I suspect that it is simply a small cylinder welded to the bottom of the tank that has very small holes at the base.
Can anyone give me a description of what these things look like.
What are typical dimensions, are there one way valves involved, do I need to source one from a wrecker . or is fuel flow simply controlled via small holes and if so what is the orientation and location of these holes?

Have a look here:

If you look in some of the speed shops in Melbourne or places like CAPA and COME racing on the web there should be leads to buy new.

For the safety aspect I would have the new stuff and avoid the wreckers on this one.

Try Brown Davis Austomotive in Melbourne for a new tank. They do a lot of LPG conversions and may be able to help with what you are looking for.

BBBWWWAAAHAHAHAHAHA...Quickly Igor...the switch throw the switch...tre storm nears it's peak!!

Sorry - couldn't help myself there.
Cheers, Pete.

Peter Thomas

Contact details for Brown Davis Austomotive:
Brown Davis Automotive
47 Holloway Drive
Bayswater Vic. 3153
Tel: 03 9762 8722
Fax: 03 9762 9829


Cheers, Pete
Peter Thomas


I have emailed you a photo of an in-tank swirl pot removed from what I think was a Ford Sierra. Its about the size of a small saucepan with a 1/2 inch fuel pick up going into the middle and a narrower fuel return squirting into a small curved pipe that enters the bottom of the swirl pot. Its a lot clearer looking at the photo, but the theory is that when the fuel is below the top of the swirl pot it keeps a resovoir of fuel for two reasons:
(1) it can seep in through the short curved pipe because it has a larger bore than than the small return pipe (especially important if the fuel pump is not running, e.g. parked with one third full petrol tank )
(2) the flow of returning fuel both fills the swirl pot and makes it hard for the fuel to simply pour back out through that curved pipe when cornering.

As for thermostatic switches, I'm not sure of the thread of the boss on the Range Rover thermostat housing. If its a standard M22 you can use the thermostatic switch from a year 2000 VW Passat 2 litre. This interestingly has two thermostatic switches built into one giving you a choice of switching temperatures, or you could wire one as a backup to the other. Can't tell you at the moment at what temperatures it switches as I don't have mine to hand but I'm fairly sure that one of the ranges is right for a V8.

Geoff Richmond

Many thanks Pete & Geoff
I will contact these guys, I'll send Igor to 'aquire' the appropriate organ then make the transplant.
I got your email,
Does anyone know if we have anything like a ford sierra here in OZ? it doesn't sound familiar.
Ironically enough the temperature switch on the '86 Rover inlet manifold has the same thread and diameter as the '75 MGB, however the Hot wire '95 thermister appears much smaller. Ironic because I had to discarded one of these earlier manifolds as too corroded to use. If I had known of the problem I would have drilled and tapped a new thread how ever now am reluctant to remove the inlet manifold for the third time. Future V8 converters take note.
Does anyone know how exactly a temperature sender works? I would guess that it is essentially a temperature dependant resistor, and if it is and since it's sending/allowing too strong a signal (ie the resistance is too low) then if I wire in a variable resistor I can adjust the guage to whatever I like.

This thread was discussed between 13/01/2003 and 14/01/2003

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