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v8 cooling 3.9 rover

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Ricey30 Avatar
Ricey30 Phil R
Chessington, Surrey, UK   GBR
It works !!

1. Still need to fit stat
2. Still need to swap inlet and outlet on heater (thanks mike)

But with new 12” it holds at 90 with Bonnet on. If I engage the secondary fan drops to 85

Very happy

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ex-tyke Avatar
ex-tyke Graham Creswick
Chatham, ON, Canada   CAN
1976 MG MGB
Quote: Back of the manifold should go to bottom of heater as the feed. Return from top of heater to the water pump
Correct - heater supply should always feed the bottom of the matrix to promote de-aeration.

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Ricey30 Avatar
Ricey30 Phil R
Chessington, Surrey, UK   GBR
I meant to surmise but deleted my ramblings before posting!

For those following on with the same issue, these were my faults as I now see it

1. dodgy thermostat
2. vacuum advance pipe connected to wrong nipple on dizzy causing timing to be sooo far out the headers started melting the shock absorber covers!
3. cheap 12" fan from ebay
4. top heater hose plumbing wrong.

I now have the car moving under its own power pending getting off the drive and to the MOT station over the next couple of days. Being pessimistic I expect a few gremlins and a fail on something.

But hats off to all of you on this site who have built cars the same or more complicated, it is not as easy as the book written 20 years ago suggests, and I have learnt the hard way that doing a conversion like this, on a driveway, with no garage and only mechanical knowledge experienced on Minis 30 years ago is not easy.

I am happy to admit that I probably bit off more than I could chew. Without the knowledge of you guys on this forum, this project would never have got finished.

I wish I had joined earlier and asked more questions about many elements rather than struggling on in the dark.

Well, I've yet to drive it properly god only knows what issues it will give. But for now its off axle stands and not over heating and moving!

Thanks to all of you, and Ill keep you posted


Phil

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Denis Avatar
Denis Denis Hill
Bearii, Nth Victoria, Australia   AUS
Great, Denis



68 B roadster, Daffodil yellow, supercharger, Burgess SC head, SC cam, Mikuni HSR 48 carburetor and engine built for supercharging.

73 BGT V8 conversion starting with a bare shell. Built the engine "3.9L Rover" early in 2016 with high comp pistons and a few other nice bits, plus a T5 ford trans. Started on the body late 2016 and complete late 2017, Did all the work myself, mechanical, body. paint etc.
Finished and going well, great to drive and quick. Now has a nice 3.23 LSD.

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Ricey30 Avatar
Ricey30 Phil R
Chessington, Surrey, UK   GBR
Gentleman I have MOT!!

Now the fun starts along with sorting all the bits that will now present themselves


Thanks again

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Ricey30 Avatar
Ricey30 Phil R
Chessington, Surrey, UK   GBR
Gentleman I have MOT!!

Now the fun starts along with sorting all the bits that will now present themselves


Thanks again

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rficalora Avatar
rficalora ROB FICALORA
Willis, TX, USA   USA
1976 MG MGB V8 Conversion "MG MUTT"
Congrats Phil! Big step. Have fun sorting it. Don't get frustrated; stuff will come up. Just knock them down as they do & before long you'll be comfortable driving it anywhere!

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Ricey30 Avatar
Ricey30 Phil R
Chessington, Surrey, UK   GBR
Final update

All good I’m running 82 degree thermostat, 88 degree fan switch in top hose (prob wrong place) 12 inch fan activated by switch rated at 790cfm.

Secondary 7inch fan off a switch manually operated by me.

It sits at 90 degrees in traffic going up to 100. I then hit the secondary fan and that works a treat.

When running it sits at 85

Still got to put antifreeze in and drill a bypass hole in thermostat but otherwise I’m very pleased.

Thanks to you all

Phil

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Ricey30 Avatar
Ricey30 Phil R
Chessington, Surrey, UK   GBR
Hi Guys

Back again same issues on cooling.

I ahve re read all of your posts re this annoying prob. Having been driving it a bit and managing to break the prop shaft in the process, I have now sorted all the bits left and want ot get to a rolling road.

Only prob is the overheating, just isn't reliable. When running hard and moving gauge sits happy 85-90C. when in traffic the 14" fan kicks in at 82C and it can control it for 5 mins but it starts to creep up. Then I turn on the 10" manual fan and it can help it. But by now its up to 100-105C.

Testing today just sat idling on the drive in 10C English morning, with the bonnet shut it was up to 105 in about 15min from cold.

I'm convinced its bled properly as on warm up top hose stays cold then gets hot on stat opening, there is water in the top hose when I undo the fan switch and the expansion tank is half full.

Once it has got up to 105C the top hose is very hard.


All you guys run with no issues like Glenn and Denis in extreme heat unlike us Brits!


Can it be the Ebay rad is basically shiny and useless as no where near enough capacity even though says for V8 MGB?

Can it be the timing is out and it is running either lean or rich, can this cause such extremes?


It runs and pulls brilliantly, as for hearing pinking I've no chance over the roar of it!!


Opinions please and I appreciate all critique

Cheers Phil


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allanreeling ALLAN R
RANDLAY, TELFORD, Shropshire, UK   GBR
Phil ,
1. With the stat out and no restrictor, it won't cool as well, as the coolant goes through the rad too quickly.
2. You're putting a lot of faith in the accuracy of the temp gauge. They're not that accurate. Get an infra-red thermometer and check.
3. Is it boiling? If not it might not be that bad.
4. Check that numbers 5 and 7 ignition leads are well separated. Cross firing will cause over-heating.
5. Running weak will also cause over-heating. Running a touch rich is no bad thing. Check that the vacuum advance is working and that there are no leaks on the servo vacuum line and those connections and one way valves..
6. Mine wouldn't idle with the breather connected to the front of the Edelbrock, I guessed it was running far too weak, as using the mixture screws couldn't get idle down to 800rpm, or anywhere near it. Maybe a restrictor would have helped, but these engines are heavy breathers and I got obsessed with over-providing crankcase breathing. I have two filters on the crankcase and both rockers connected to the filter can, inboard of the filter element.
7. My 3.9 runs at a reasonable temp and is well controlled by 2 x 10" pushers.



soonerv8

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260mgb Jim Nichols
Sequim,WA, USA   USA
Phil, you may have air pockets in the system. Try filling with the heater valve open and the front end up on jackstands. Also the Edelbrock Performer intake manifold lacks the two small holes that the Buick and Rover and Offy intake manifold have in the thermostat opening.

http://forum.britishv8.org/read.php?6,57097



Edited 1 time(s). Last edit at 2019-02-23 12:09 PM by 260mgb.

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Ricey30 Avatar
Ricey30 Phil R
Chessington, Surrey, UK   GBR
Gents

Think we’ve solved it!!


following Allan’s advice I got a lazer temp sender great bit if kit. This confirmed liads if things including that the smiths gauge is reasonably accurate.

I would get 90c at the inlet manifold where the sender sits and that matches the gauge. Also that the temp at the top hose changes at the right degrees for the thermostat, as does the otter switch operating at 82c.

So far so good, then to my surprise the main fan is not kicking in, nor the manual fan. So trace that back to a blown fuse. Now that works ok it controls the engine better but still creeps up past 95 and on to 100c +.

The one big problem I think i have is that the “expansion tank” I use has the pipe from the top of the rad entering at the bottom of the tank. Completely different to the MGB original expansion tank.

Plus I learnt from the supplier that the only difference between the standard 1.8 rad and the V8 rad is the outlet pipe positions.

So I’ve borrowed a standard Mgb expansion tank and fitted it at the back of the engine bay ABOVE the engine, so the inlet to the tank is above the outlet at the top of the rad.

Now when I fill up the rad it fills to the brim and then pushes the air up and out via the expansion tank.

Could it be that my shiney expansion tank wasn’t allowing expansion properly and was just creating airlocks ?

As it stands it’s behaving at 100c and I will try leaving it again tomorrow and see if it holds up.

Do you guys think that the expansion vessel may be the solution ?

Cheers

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Denis Avatar
Denis Denis Hill
Bearii, Nth Victoria, Australia   AUS
Phil, do you top up the radiator filler when cold. I have, I think the same header tank as you and its slightly below the rad and no problem with the pipe going to the bottom of the tank. It has to to recycle.
Hope I havn't jinxed myself as I have a long drive today in 40*c. I live in the sticks so the car rarely sees traffic but when it does the two 9" pusher fans have no trouble. Normally they hardly ever run. I did have a problem when I first fitted the fan electronic sensor, fitting it at the engine end of the top hose with the plug wires passing over it. Stuffed around and could not work it out. Contacted the maker and they tell me its sensitive to HT in close contact. Fitted it to the rad end of the top hose and no problems since ( 15 months) That was something I had forgotten and worth keeping in mind.
Denis



68 B roadster, Daffodil yellow, supercharger, Burgess SC head, SC cam, Mikuni HSR 48 carburetor and engine built for supercharging.

73 BGT V8 conversion starting with a bare shell. Built the engine "3.9L Rover" early in 2016 with high comp pistons and a few other nice bits, plus a T5 ford trans. Started on the body late 2016 and complete late 2017, Did all the work myself, mechanical, body. paint etc.
Finished and going well, great to drive and quick. Now has a nice 3.23 LSD.

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Ricey30 Avatar
Ricey30 Phil R
Chessington, Surrey, UK   GBR
Hi Denis

My sensor is nearer the rad in top hose so away from the leads.

Something else I’ve pickedup on having statrted on my mates mg 1950cc, is my shiney sits way higher than his due to the mounting flanges on the rad hitting the bottom chassis rails. My bonnet only closes because I hand the mgc bonnet on it.

So another tweak to replicate the original install is to trim the rad flanges down so the rad sits lower ? But that would mean my big fan won’t fit .....,


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JIMBV8 Avatar
JIMBV8 Jim Gibson
Northampton, Northamptonshire, UK   GBR
Pipe entering the expansion tank at the bottom is correct. The MGB one enters near the top but continues downwards inside the tank. The pipe needs to be submerged, so that expansion pushes out any air if there is any, but sucks back coolant.

Original mounting of the expansion tank for GT V8 is below the top of the radiator, not a problem.

Variations in the tanks - physical shapes, pipe connection point, position and angle of pressure cap - were simply to suit fitting in different cars,
( There were some plastic ones with integral mounting lugs; and translucent -you could see the coolant level. )

Philips comment " ... your top hose looks like it rises from the inlet manifold and then drops to the radiator ..." has been the case with some conversions, the thermostat housing might be from a donor engine and so different from the original GT V8 thermostat housing with a different angle of the hose connection.

Glenn's technique of squeezing the top hose ( aka " burping the tank" ) is pretty standard, I sometimes do it in my GT V8; but Idid use to see comments that doing it too often and too enthusiastically caused internal damage to the hose.

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