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 Posted: 09-12-2019 06:33 pm
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jomac
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FYI, we always hear about replacing the diaphragm , but i also replaced the spring air valve return. it made the idle smoother and for responsive. figures; they most likely were original from 1973! moss motors sells all the individual components for zs carbs. i ordered from the tr250/tr6 catalog,they use the same 175 carb. spring #365-780. $9.99 each. check out their website.

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 Posted: 09-13-2019 08:14 pm
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PF18602
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Thanks for the tip! Wouldn’t have thought about that but makes a lot of sense. Just ordered a couple; hoping that it clears up my issue of the rpms increasing as the engine gets a little too warm. If it doesn’t work, next step will be an electric fan on the radiator.

Patrick

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 Posted: 09-22-2019 06:26 pm
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jomac
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i had the same issue, higher idle as it warms up, spring change appears to keep the idle more constant. regarding your radiator fan, i just installed a 10" pusher fan in front of the radiator ( between rad and oil cooler). i set up a manual on/off override switch under dash. i installed the thermostat on the heater hose line on the driver side, bought a brass tee adapter and a reducer ( hardware store) for the switch.

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 Posted: 09-22-2019 11:54 pm
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PF18602
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That’s exactly what I’m thinking about installing. Car came with a pusher fan when I bought it, but took it out in the hopes that it didn’t need it. Seems that it wants to be running cooler. Bought a setup to have a thermostat switch inline on the top radiator hose, but the heater hose is an interesting idea. Is that the hottest place and therefore the best for the switch?

What temp range did you get for the switch?

I just used an infrared thermometer to check temps in various places, and the hottest was on top of the thermostat and read 185-190. So seems temperature isn’t an issue, but hopefully the fan will help a bit if I get the right temp range for the switch.

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 Posted: 09-23-2019 02:54 am
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Esprit2
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There is little, if any flow through the heater circuit when the heater valve is closed. Putting the fan's thermo-switch in the heater circuit may work well in the Winter, but in the worst, hottest Summer day, you probablly don't want to drive around with the heater on. Just a thought.

If your engine runs too hot in your climate, also consider rebuilding the water pump, using the impeller from a 910 Turbo pump. The nose is longer, so it won't fit as received. Take it and the old impeller to a machine shop, then have them cut the Turbo's nose down to match the 907's.

See the attached JPEG, and note the increased number of longer vanes. It moves much more coolant. Still make certain the radiator is in good, clean condition, and a supplemental electric fan wouldn't hurt, but the 910 impeller is a big plus.

Regards,
Tim Engel

Attachment: Cooling - Water Pump - Impeller - 907 left & 910 right - side, Notes.jpg (Downloaded 90 times)

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 Posted: 09-23-2019 03:00 am
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Esprit2
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See the attached JPEG. Note that both the 907 impeller on the left, and the 910 impeller on the right have backward curved vanes (the impeller rotates clockwise). Early 907 impellers had forward curved vanes, which caused cavitation at higher rpm, and led to over-heating.

Whenever you rebuild an early 907 pump, make note of the vane's direction of curvature. If they curve forward, then replace it wil a later impeller. Either a later one meant for your pump (small vanes), or a 910 impeller with the longer vanes.

At some point in time, Lotus metricated the water pump. The impellers are available with both 1/2" and 12mm ID bores, and the bearing shafts & seals are available with matching diameters. Either inch or metric can be used equally well in your early, inch pump housing, as long as you specify the bearing and seal with matching diameters. Buy in 'sets'.

Regards,
Tim Engel

Attachment: Cooling - Water Pump - Impeller - 907 left & 910 right - high 94kb.jpg (Downloaded 91 times)

Last edited on 09-23-2019 03:06 am by Esprit2

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 Posted: 09-23-2019 02:47 pm
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Esprit2
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Sorry about the sudden left turn... the thread is 'Carburetor'. But jomac mentioned putting a fan thermostat in the heater hose line, and, well... I'm easily influenced.

Regards,
Tim Engel

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 Posted: 09-23-2019 11:13 pm
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jomac
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my electric fan came with a 165 -185 thermostat, my heater hose line had old rusted out manual on/off valve which i removed to replace with my thermostat tee fitting. (ps the valve was rusted in close position). michigan temps are not that warm, so needing a heater is required. during the summer i keep my dash heater slide bar set to mostly defrost setting or closed.ps if your heater valve is working, putting the thermostat forward of the valve should not affect its performance even if the valve is open or closed position.

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 Posted: 09-24-2019 03:38 pm
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redracer
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Tim: with the advent of the 3G seal that Dave Bean has, the nose of all the impellers can be ground down/hacksawed with impunity, as the nose no longer needs to press down the seals. Do the LOTUS impellers have the same shaft diameter as the older 907 engines used.
thanks, bruce

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 Posted: 09-25-2019 02:17 pm
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Esprit2
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Bruce,

Yes, I use the 3G type of seal exclusively for my own work. But the old seal is still out there, so rather than get into a seal by seal discussion, I just tell people to cut the new Turbo impeller to match the old impeller's length. If a hacksaw is used, the cut should at least be 'square', clean and smooth, as in, dress it with a grinder. It will still be spinning in a fluid, and any truly ragged or angled edge can cause a localized turbulent flow that could contribute to cavitation. Keep it smooth.

Early Lotus shaft diameters are the same as Jensen-Healey's... 1//2" Later, Lotus metricated the pump, and the impeller shaft & bore became 12mm. The front shaft/ hub diameter, and the bearing OD/ housing bore were unchanged. So either bearing, 1/2" or 12mm, can be used in your older J-H pumps, as long as you buy an impeller with a matching bore.

The main thing to watch for is impeller shaft length. The bearing isn't a one-size "Lotus" part. It's a fairly common 'type' of bearing, with many shaft length combinations. And it seems that the many different Lotus & J-H parts specialists are buying "close but not quite" bearings where they can get the best deals, and they're not all selling the same bearings. I've seen a variety of bearings sold for 907 pomp applications that have different impeller shaft lengths.

The ones that worry me are, IMHO, too short to have an adequate depth of engagement with the impellor. I heard from one J-H owner who received such an impeller, wondered about engagement, but used it anyway. Later, the impeller fell off the shaft within the pump while he was driving the car. Of course, with zero circulation, the engine quickly over-heated.

Regards,
Tim Engel

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 Posted: 09-25-2019 02:44 pm
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redracer
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Tim:
thanks for the fast reply; for a while in the mid '90s, all the impeller shafts were short, so I tack welded the impeller to the shaft inside(no problems, thank goodness). I had 2 original pumps from one of my dealer buy-outs that had the longer shaft which Dave Bean wanted, but I didn't want to give them up, and now there are longer shafted one available.
I assume the angle for the impeller-to-housing is the same and wonder if anyone has done a flow test to see how much more water is flowing through the LOTUS impeller vs. the original J-H impeller?
Just returned from the JENSEN nationals in St.Louis("HOT"); lots of nice cars with many updated Madera Concepts dashes and upgraded engines for the 907s.
take care, bruce

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 Posted: 09-25-2019 03:34 pm
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Esprit2
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redracer wrote:
...for a while in the mid '90s, all the impeller shafts were short, so I tack welded the impeller to the shaft inside(no problems, thank goodness). I had 2 original pumps from one of my dealer buy-outs that had the longer shaft which Dave Bean wanted, but I didn't want to give them up, and now there are longer shafted one available.Bruce,
The 9XX 4-cylinder engines are decades out of production, and Lotus hasn't provided many of the parts for a long time. We rely on the independent Lotus & Jensen-Healey parts specialists, and I really do appreciate their efforts. But it would sure be nice if they would put their heads together on some items (like the water pump bearing) and agree on a common, 'correct' configuration.... like a long impeller shaft.

The attached JPEG shows the difference in shaft lengths between two bearings I received from different vendors. Note that the bearing's OD is smooth on one, and has two grooves around it on the other. I have another bearing with one groove, and it's impeller shaft is yet a different length. And they're all sold as being "Lotus" water pump bearings.redracer wrote:
I assume the angle for the impeller-to-housing is the same and wonder if anyone has done a flow test to see how much more water is flowing through the LOTUS impeller vs. the original J-H impeller?They all appear to be the same. The Turbo impeller nests into the housing like it belongs there... once you shorten it's nose.

I've never seen any published performance specs for the various 9XX water pumps... like flow rate and pressure. Conversationally, the Turbo water pump was said to be a flow-rate upgrade that was required to keep up with the heat load of the 910 Turbo engine. Besides the impeller, the pump's scroll housing was enlarged to better accommodate greater flow. How much greater? No clue. But it's also said that if you don't wish to deal with some of the other issues involved with swapping-in a full Turbo pump, that just installing the Turbo impeller into a 907 pump housing will produce about 70% of the flow improvement... however significant that improvement is. I can say from experience that the 910 impeller in a 907 housing does make a difference.

Once the improved pump was tooled-up, a slightly modified version (machined off a large boss) was also used on the 912LC & 912HC. "IF" you were to install a 'Turbo' pump on your 907, it would be better to buy the 912 version without the big, intrusive boss... it's a more direct fit. I just speak of Turbo impellers all the time, since the 912 was never sold on this side of the pond, but Turbo Esprits were.

Regards,
Tim Engel

Attachment: Water Pump - 9XX Parts - Bearing.jpg (Downloaded 68 times)

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 Posted: 10-01-2019 08:38 pm
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redracer
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Tim: I would like to try the later LOTUS impellers on some water pumps, but I have absolutely none(have plenty of the original ones though). If you have any used ones, I would like to purchase a bunch for testing. I don't have your personal email, so please email me at :
RedRacerbm@gmail.com
thanks, bruce

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 Posted: 10-05-2019 05:30 am
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PF18602
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Thanks for all the info, Tim. Very informative. I second Bruce’s request; I’d love to get an impeller from a 910 and try it out on my car when I rebuild the water pump. If anyone has one available, let me know! I have a mkii from fall of ‘74. Four speed. Email is Patrick.farrell90@gmail.com.

Thanks!
Patrick

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 Posted: 10-09-2019 03:43 pm
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Esprit2
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Bruce & Patrick,
Sorry about the late reply, but I've been travelling. I'm a troglodyte with a dumb phone, so when I leave home, I leave email and the internet behind.

I don't have a stash of old 910 impellers, I just buy one when the need comes up. JAE has had the 910 impeller re-produced, and has about 500 in inventory. They're reasonably priced.

That's the good news. The 'minor' bad news is that the snout/ center boss on many of them leans off to one side a little. It looks like they were removed from the mold too early, while they were still too hot, and it sagged off to one side.

They work, but I wonder if the slight off-center lobe doesn't aggitate the coolant flow. So when I send it off to the machine shop to have the nose shortened to 907 length, I also ask them to turn the nose so that the outside is concentric with the bore. Just press the impeller onto a steel rod, chuck the rod in a lathe, and lightly cut the snout's OD. No big deal.

Brett Gibson has installed a 910 impeller in his JH water pump. Ping him, and ask for his opinion.

Later,
Tim

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 Posted: 10-10-2019 01:42 pm
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Brett Gibson JH5 20497
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I re-built a pump using the 910 impeller for a car under restoration and have yet to install and fire up the engine. But I have to say that the design and longer impeller vanes on the 910 almost certainly will increase the flow, they are about twice as long as stock, and have a better flow pattern. It would be nice to see a pump curve for the 910 verses stock to put a real number on what to expect in flow, but as a Field Machinist for a number of years specializing in pumps, I would expect a greater volume flow thru it.
Brett.
PS. anyone who wants a photo of a 910 verses stock PM me with your e-mail. I'd post one here but can never get it to work.

Last edited on 10-10-2019 01:44 pm by Brett Gibson JH5 20497

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