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Lotus Water Pumps  Rating:  Rating
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 Posted: 05-21-2005 05:11 am
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Jensen Healey
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I understand there is a Lotus Esprit water pump that has an extra port for the hose that connects to the tap on the rear of the head. On the JH the tap is not drilled but you can see the raised area where it should be on the left rear of the head. Some people have tapped this and connected it to the heater return line.

I would like to maximise cooling performance when I install the 107 cams.

Do all Esprits use this water pump or are there specific years or models?

Kurt Housh

JH 13148

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 Posted: 05-21-2005 02:39 pm
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Mark Rosenbaum
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Quoting Tim Engel from something he wrote years ago:


[ ...]  In the turbo engines and later 912's that use the uprated turbo water pump, the frost plug is replaced with a pressed in nipple. A 3/4 inch 90 degree molded hose then connects it to a second water inlet to the turbo pump. This provides another return flow path back to the water pump in addition to the one through the intake manifold water passage and cools the head better.  [ ...]  If everything else was fine, the turbo pump would provide a little extra cooling for a safety margin on hot days.




It's my understanding that moving the heater takeoff spigot from the middle to the rear of the head will increase the coolant flow through the rear of the engine, provided the heater shutoff valve, if present, is open -- but has no effect if this valve is closed.  This being so, a first step would be to remove the shutoff valve  Note that the heater core would not be of any use as a supplementary radiator unless air were flowing through it, which in turn would mean that the cockpit would end up very hot in summer.  This is unlikely to be desirable.

I think you'd be better served by using a larger radiator than by trying to use the additonal spigots on the turbo pump in conjunction with a heater core to provide supplementary cooling.  However, the turbo pump, with the spigots replaced by freeze plugs, apparently does provide better cooling than the earlier pumps -- my car has no overheating problems in street driving even at ambient temps above 100^F, and it has some sort of post-JH water pump installed (though I'm not sure which one as I can't see the casting number). 

When next your water pump is removed, you may wish to examine the rectangular hole at the rear of the water pump cavity, through which coolant flows into the block.  These holes are very small, and the factory typically opened them up quite roughly with a chisel, so they offer a huge restriction to coolant flow.  Even a very small amount of 'porting' with a die grinder or a file should improve things tremendously.

Finally, regardless of version, water pump performance depends enormously on the clearance between the impeller vanes and the tapered region of the pump casting.  This clearance is quite small (only 0.020" IIRC), and perhaps not every rebuilder holds to the spec.  It would be prudent to check the clearance before installing any new water pump.

 

Attachment: water pump lotus late #1.jpg (Downloaded 139 times)

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 Posted: 05-21-2005 06:39 pm
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Judson Manning
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Kurt,

I'm going to agree with Mark in that the pump probably isn't the area that needs the most improvement.  As long as you have a quality rebuild and the impeller to housing distance is within spec, the turbo pump probably won't give you much improvement if other elements of your cooling system are maxed out.

The Aluminum / Brass radiator debate has raged on this board numerous time, and with that said, we don't need another comparison thread.  However, the lesson here is to understand is that a poorly designed or built radiator is just a bad radiator, no matter the construction material.

After 3 rebuilt/re-cored JH radiators, I threw in the towel and adapted an aftermarket radiator.  It's smaller, has only 2 rows, and is made of a material that conducts heat worse than the JH radiator, but my cooling problems are solved.

If I had an unlimited budget, I'd have someone like Griffin build me a custom radiator using the same magic they have that keeps NASCAR machines from overheating.  Alternatively, the Jensen GT uses a larger radiator and it wouldn't be difficult to adapt one to a JH.

Judson

 

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 Posted: 05-22-2005 05:33 am
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Esprit2
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I have a Word.doc containing information on Lotus water pumps and rebuilding. It's not written with Jensen-Healey in mind, but most of it applies.   Is there a section on this list for posting files?

The Turbo water pump does flow more coolant than the standard 907 pump.   Of course,  that's all for naught if the radiator isn't up to snuff.   So I agree with the importance of tending to the radiator first.   However,  if you're running a hotrod engine or live in a hot climate,  then the Turbo pump can provide an additional increment of cooling.

Differences are:

1)  a larger scroll housing.

2)  a revised impeller design that solves cavitation problems and improves flow.   The impeller is a direct fit into older housings.   Switching to the Turbo impeller alone during a pump rebuild will give about 70% of the flow improvement of a full Turbo pump.   The impeller costs about $40.   The full Turbo alternative isn't cheap.   New is about $450 street price (~$900+ full Lotus list).   Or shop for a used pump and install a rebuild kit…  of course,  it will already have the Turbo impeller.

3)  two additional 5/8" hose spigots… one for a heater hose return and one for that 90° elbow hose direct to the cylinder head mentioned in the clipping above.   The elbow hose was added to increase coolant return flow to the pump for improved cooling.

I guess you could use the heater spigot at the rear of the head to increase cooling flow,  but at the loss of the heater.   Just shunt a hose from there direct to the second spigot on the pump.

The hose and spigots are 5/8",  not 3/4" as I wrote in that clipping.   My Esprit and Eclat have heater returns elsewhere,  making the one on the pump was redundant.   So I just removed it and plugged the hole with a standard 5/8" frost plug.   I live in the north and wasn't willing to give up the heater to get a small incremental increase in cooling.   Compared to the original 907 pump,  the Turbo was already giving a much larger incremental increase,  so I wasn't too worried about not taking advantage of shunting the heater.

The thermostat neck is not in the same place or the same OD as the Jensen-Healey's,  so you'll have to be creative about finding a hose that will fit.   The various Lotus pumps all seem to have different T-stat housing configurations.   The T-stat housings are forward on some and back on others,  and the bolt patterns are different (rotated).   All the various outlet housings will bolt on,  but the outlet won't be in the same place or pointing the right direction.   Not to mention that a J-H  T-stat housing on a 910 pump would interfere with the timing belt.

The Turbo housing points to the right. The Excel SE (912 HC) used a similar pump and the T-stat housing pointed forward.   That housing might be the better choice for the J-H since it angles forward,  right and down a bit.

The Turbo pump has a large cast boss at about the 5:00 O'clock position for mounting a vacuum pump… the Excel pump doesn't have that.   Otherwise they are the same.   That's a minor point since both will fit.   But in the J-H, the big boss with nothing installed will always look like something is mission.

Lotus used electric radiator fans.   If you wish to retain the J-H engine driven fan,  the pulley hub will have to be transferred to the Turbo pump.

Lotus Elite/Eclat 907's used a 5.25" OD, shallow bell pulley.   The Esprit variants all used a 4.5" OD, deep bell pulley to spin the pump faster.   The hub must be pressed onto the shaft to different depths depending upon the pulley used such that the V-belt groove aligns with the one in the crank pulley.

If you can find a rebuildable core for a sane price,  the Turbo pump is worth it.   But if the alternative is to buy new,  I'd install the Turbo impeller into the original 907 housing and put the money saved toward an thicker core radiator and an oversize electric fan.

A912E9055J   Excel SE & SA  912 HC   /   A912E9164F  T-stat Housing.   Heater return spigot is straight...  pointing forward.

B912E9021J   83-87 Carb Turbo   /   B912E1829P  T-stat Housing.   Heater return spigot is a 45° elbow...  down to the left.

A912E9055J   88-92 Injected Turbo   /   A912E1829K  T-stat Housing.   Heater return spigot is a 45° elbow...  down to the left.

A912E9277J   93-97 Injected Turbo   /   A912E1829K  T-stat Housing.   Heater return spigot is straight...  pointing forward.

All the turbo pumps are basically the same.   Different part numbers generally reflect differences in hubs & pulleys.   Taken as total lumps,  they're pretty interchangeable

The spigot that replaces the frost plug in the front of the cylinder head for the elbow hose is no longer available.   But I have a drawing of it and you could have one turned from bar stock.

Good luck,

Tim Engel

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 Posted: 05-23-2005 04:49 am
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Jensen Healey
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Thanks guys,

To be clear, I personally don't have any cooling issues. The four core radiator is doing it's job and the engine still fairly new. I do love trying to improve the performance and reliability of my car especially if it's a low-buck mod. It looks like the turbo impeller is the way to go.

It seems to me that a shunt in the heater line with a valve in it is the simple solution to the return line issue. In summer with the valve open the heater would work poorly but should still work. In winter with the valve closed the heater would work normally. Maybe I could connect the valve to the un-used choke cable for on-the-fly control.

Gee, this sounds like fun...

Kurt Housh

JH 13148 was at the Dixon All British Field Meet today. 4 Healeys, 4 ints, and 1 GT

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