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MG Engine Swaps Forum

v8 cooling 3.9 rover

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Jim Blackwood Avatar
Jim Blackwood * BlownMGB-V8
Gunpowder Rd, Florence, KY, USA   USA
You might consider using a surge tank instead of a recovery bottle. Reason being, a surge tank actively removes air from the system and keeps it full.

Jim

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Ricey30 Avatar
Ricey30 Phil R
Chessington, Surrey, UK   GBR
Taking all these points on board and having got the cat back after the clutch fiasco. I’m going to reinstate my catch tank seeing as Denis runs in Oz with it. Make sure the tank isn’t over full, then fill via the top hose where the otter switch is, which in theory will allow the air to bleed up and out as it’s the highest point?

I bet I get another pint in that way.

I presume with the cap on the expansion tank, water can’t feed into the tank as I’m filingut up from the otter switch ?

Phil

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Ricey30 Avatar
Ricey30 Phil R
Chessington, Surrey, UK   GBR
Ok progress

I refitted the original Ali exp tank and applied the physics of expansion and this time filled the expansion tank up to leave the same amount of air at the top, as the equivalent original expansion tank had. This would replicate the original cars available space for expansion and subsequent pressure build up would raise the boiling point of the coolant.

Ran it today did over 50 miles and highest it got was 95 sat still for 15min, and I didn’t need the second fan at all. When driving it dropped to 80 and stayed there.

I still haven’t drilled the bypass holes in the edelbrock manifold to eliviate the hot spot round the temp sender.

Could it be that where I had prob 1.5lit of air for expansion in a 2lit expansion tank, now I have 1.5 lit water in the exp tank and 0.5 lit of air, it appears to behave itself.

Love your educated opinions ......

Phil

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Denis Avatar
Denis Denis Hill
Bearii, Nth Victoria, Australia   AUS
Phil the expansion tank should fill from the rad top tank. I may have got it wrong?



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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Cornfgl Avatar
Cornfgl Graham Cornford
Bellville, TX, USA   USA
1974 MG MGB GT V8 "Goose Poop"
Phil,

When filling my factory V8 with coolant, I have always lifted the front of the car as high as possible, to get the radiator filler higher than the top hose. I feel that this technique eliminates the need for burping. With the 15 lb cap on the expansion tank, I fill through the radiator filler until it is full to the brim. Once sealed, I lower the car, and I go through a heating cycle, then let her cool down, then lift and fill up the radiator again, then check the expansion tank is no more than half full.

I assume that the 3.9 is similar with an expansion tank in that when cold, it should not be more than half full, otherwise it has a tendancy to syphon coolant out. I made a small marked stick for that which I keep in my tool box.

Throughout this process, I also enlist the aid of a small coke bottle, which I hang from the top hose with string with the expansion tank overflow pipe into it, which allows me to check if in fact I am loosing coolant, or retaining it all. Without the bottle in place for a few test runs, I am uncertain as to if I am retaining the coolant, or spreading it all along the highways and byways. This is my way of getting a difinative answer.

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Ricey30 Avatar
Ricey30 Phil R
Chessington, Surrey, UK   GBR
Graham you prob could have described thevgilling sequence I have, as my drive is on a slope and the front of the car is way higher than the back. So by default I reckon it has by sheer luck burped itself. My filling cycle has taken several days due to weather kids life etc and fir the first time this weekend but didn’t really need topping up. I reckon it’s had a good 1.5 liters into it, therefore prob been under filled.

Denis the take off for the exp tank is next to the top hose at the top side of the rad, then goes to the bottom of the exp tank.

I haven’t checked levels since driving it so I might do that as Graham suggests with a stick.

But its looking like it could be a combination of enough fluid in the exp tank and a full system. As it seems a huge difference has occurred when nothing else has been played with.

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Cornfgl Avatar
Cornfgl Graham Cornford
Bellville, TX, USA   USA
1974 MG MGB GT V8 "Goose Poop"
Phil,

Don't forget your coke bottle, it will tell you of the car is vomiting!

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Denis Avatar
Denis Denis Hill
Bearii, Nth Victoria, Australia   AUS
Phil thats the same as mine. Pressure cap on the aloy tank. I have not topped mine up in 12 months, although I do check it cold now and then. 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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