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Header/Expansion Tanks


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Just finishing up a few bits on my V8 conversion.

The header tank thats on my Landy is the original one from the 2.25 petrol and has 2 pipes connected. One thin one from the top of the rad and a larger one in the bottom of the tank that feeds back into the old water pump I think. Ive blanked the bigger one on the bottom off.

Now, ive done the V8 conversion there is knowhere for the bottom one to feed back to. Ive connected the top one to the rad again and T pieced in the pipe from the front of the thermostat housing (See my other post in wanted for the small rad fitting needed).

Now my question. If the new system gets hots and expands water into the tank, how does it ever take it back into the engine/rad when the pipe is right on the top of the expansion tank?

Are there 2 kinds of tanks? Expansion and header? (2.25 running a header and V8 running expansion)

Are the tanks different inside? Like the V8 expansion tank has a pipe inside reaching to the bottom of the tank to enable expanded water to return back to the system?

I just dont see how it could ever get back on my tank?

Do I need to get a proper expansion tank for the V8 system?

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Just been to look at the bits from my (ex) carb V8 install.

1) The header tank has one pipe out of the top, this connects to one of the small tubes top right (from driver seat) of the rad.

2) The second small tube (adjacent top right of rad) connects to the inlet manifold (a tube in the lump of square metal between the 2 SU's). i.e high up on manifold.

3) The rad has a plug in the top of it for bleeding/filling.

I could never fill the system using just the expansion tank. Always had to use the plug on the top of the rad. I guess therefore that there is some land rover technology in the header tank just to handle expansion and contraction of the water level.

FYI - The 3.9 I am putting in had a different tank with a feed off the bottom that T'd into the main bottom Rad pipe.

These are clearly 2 different systems. I am guessing here, but because the carbed version tank has to fill from a top feed, there must be something in the tank, whereas the later RR version relies on gravity to the bottom tube.

While I am pondering my other issues today, I will experiment with the header tank to see if there is an internal tube to the bottom.

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Highly scientific experiment just carried out!

Blowing into the tube that goes into the top of the header tank, I filled up the tank until there were bubbles. These started at about 1/4 full. So, I would say that yes the feed does go down 3/4 into the header tank.

I would say that you have 2 options. (1) To find an original V8 carb header tank (or test yours to see if it does the same thing) or; (2) probably easier to find one of the standard range rover bottom rad pipes, with the T'd off tube to run up to the bottom connection on your header tank (that you have blocked off).

Hope this helps.

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Highly scientific experiment just carried out!

Blowing into the tube that goes into the top of the header tank, I filled up the tank until there were bubbles. These started at about 1/4 full. So, I would say that yes the feed does go down 3/4 into the header tank.

I would say that you have 2 options. (1) To find an original V8 carb header tank (or test yours to see if it does the same thing) or; (2) probably easier to find one of the standard range rover bottom rad pipes, with the T'd off tube to run up to the bottom connection on your header tank (that you have blocked off).

Hope this helps.

Good stuff, and yes a highly scientific experiment that I will attempt to re-produce tonight when I get home!

I am hoping that mine does not have that secret landrover tube as that will be a move forward!

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