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| Joined: | 05-01-2005 |
| Location: | Minneapolis, Minnesota USA |
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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