The intake for my 4.0 (and other styles) has no water passage at the rear. The head has a channel at either end, which allows universal fit (left / right). But this allows coolant to be at a "dead end" with no flow, creating either a "hot pocket" or an area to trap "gas bubbles".

So I wonder if this design over long term allows extra heat at the rear, and contributes to the HG problems in this area. I would suppose you could drill and thread in a couple of small pipe nipples and attach tubing to route this over to the coolant jug. The valley pan gasket already has a nice big cutout for each.

 

Buzz, you may have hit on it. Does make since, are you going to be the first to try this?

 

Will think about it, seems like I may have a couple of days before a dry spell comes in. I would wonder if members with IR thermometers could measure the intake at several points front to back, and see if there is any difference?

I would suppose if I test it one method would be to drill and tap it, then install just sealed bolts. Then I could test with and without the extra plumbing. On the other hand, it may be something so modest that it is only a few degrees, may not show up with my 180F stat.

But something sure eats those head gaskets.

BTW, dead legs in plumbing systems harbor all sorts of nasty things like Legionella and it is standard practice to cut a dead leg back at the source. Even legs as shorter than 5 X pipe diameter are suspect.

 

Here is a pix of the front of the manifold. That big plug at the bottom was a heater hose on some older models. I have also looked at pix of various older Rover manifolds, and after market ones, and some show a fitting on the rear where I intend to drill mine.

My thought is to route coolant from those two dead ends to this plug on the front, where it will pass thru thermostat and radiator.

 

I'm not sure about this...

The coolant from the block goes into each side of the head, the rear port is then directed towards the front of the head, and into the intake there. By installing a port at the rear, I do think you will have slightly better flow through the rear port, but I also think you will be limiting the flow from back to front of the head, which could give you issue with heat in the center of the head.

Although, different sized fittings could be used to ensure you aren't creating too much of a 'bypass' and still allowing good flow through the head itself. If anything, I would suggest to start small, just to allow for a little more flow through that section, as I agree, it is inherently limited at that point.

Also, the port at the front of the intake is where I would hook up as well, keeps everything on the right side of the t-stat.

 

If you were to drill and tap for NPT then you could use a coupe of gas **** valves which would allow you to shut off flow or regulate it.

 

Why don't you contact Turner Engineering or RPI Engineering? I would imagine they would have some educated information on it.

 

So far my project has been held in check by the utter futility of trying to buy pipe taps at either Home Depot or Lowes, they have the NPT to b-a-r-b fittings, just nothing to install them with. Will swing by plumbing supply.... 75 miles round trip.

I agree that a large diameter pipe would starve the existing system.

I would think if there was an validity to this idea that an IR thermometer would should considerable differences on temperature along the manifold itself. I have an IR thermometer, but not a running truck to test with.

The coolant from the block is mostly entering up through the rear slot, but a hole is also present in the front, you can see the gasket outline around it on this pix. Not sure what kind of "balance" is there, certainly not a 50/50 split. Perhaps, when you consider that 80-90% of the coolant goes thru the back slot (and it a'int cool at that point), would cooling off the rear section of the head even make a difference? The cool "koolant" enters from the water pump channel, and spreads along the length of the engine, would seem to reason that back cylinders would get hotter.



Oops, sorry, I forgot this is the dinner hour. Now you know why I had to buy a gallon jug of Malox....