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Motor oil viscosoity  Rating:  Rating
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 Posted: 03-26-2015 09:22 pm
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rday
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Hello All,
  I have taken ownership of a 74 JH.  I realize this topic has probably been talked to death but when it is stated that the engine oil should be 20w-50, is this the same with all brands of oil?  Is Castrol 20w-50 the same as Napa 2ow-50?  I believe the previous owner changed the oil and used 10w-30.  I have also topped off the SU carbs with 10-30.  Should I switch to 20w-50?  I do get the occasional hesitation and sputtering while accelerating.  Could this be the problem.  I am in Northern New England in the US and I only run it in the summer
                Thanks for the input,
                               Robb

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 Posted: 03-27-2015 04:01 am
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Tom Bradley
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Hi Robb,

Welcome to the insane asylum. Sorry, I mean JH enthusiast society.

You are probably about to witness a big argument about the advantages of various types of oil, but a a first approximation, all 20W-50's are about the same and will work OK in your car. Any brand of correct weight oil will certainly be better than the most expensive oil of the wrong type. Lighter weights are not a good idea, even in relatively cool areas: this engine tends to run pretty hot.

The Stromberg carbs also require 20W-50 according to the manual. I am not sure it makes all that much difference, but the lighter weight oil could be causing your problem. In any case, using the same oil in both places certainly makes it easier. It is also possible that something like a vacuum leak or incorrect adjustment could be causing the problem.

Good luck, and again, welcome,

Tom

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 Posted: 03-27-2015 08:34 am
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subwoofer
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I'm not a carb expert, but as far as I can tell a lower viscosity oil in the carbs will shorten the acceleration enrichment period. The purpose of the oil is to slow (and dampen, probably) the venturi piston movement when airflow is increased, thus temporarily creating a larger vacuum and higher fuel flow.

I don't know how large this effect would be in practice and if it would be noticeable, I am just pondering on the theory of operation.

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Joachim

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 Posted: 03-27-2015 03:02 pm
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Jensen Healey
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Hi Joachim,
I agree. Using lighter weight oil will cause a lean condition during acceleration.

Also, these engines need the zinc (ZDDP) which is found in racing oils and motorcycle oils. I use Valvoline VR1. Use a quality oil filter like Bosch, Mobil 1, or K&N.

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 Posted: 03-28-2015 12:08 am
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rday
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Thanks All,
   Your comment on a lighter viscosity oil affecting engine temperature makes me wonder if this is why the engine runs hot.  Around town I have no problems, but any distance under load (up long hills) and on the highway (60 mph +) it does get hot.  I thought maybe that the radiator was partially plugged or it may need a new thermostat.  The first maintenance that I performed on this car was to change the timing belt and flush the cooling system.  When I pull it out of its winter hibernation, I'll change the oil using 20w-50 and top off the carbs with 20w-50.  I was also planning on flushing the cooling system again and replacing the thermostat.  Any other suggestions? 
                -Robb

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 Posted: 03-28-2015 03:14 am
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Tim Murphy
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I found that having the fan shroud and a front air dam that directs air up to the radiator helps with engine cooling. At 60mph you should not be running hot. Also make sure the basic timing is close to stock. Some like to over advance the timing which gives a bit more performance but can cause a lot more heat. Link to some basic info:
http://www.freeasestudyguides.com/ac-fan-shroud-air-flow.html

Last edited on 03-28-2015 03:15 am by Tim Murphy

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 Posted: 03-28-2015 08:12 am
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subwoofer
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It would not surprise me if your radiator is clogged. Run it up to temperature and spray water on the radiator. It should dry out evenly, vertical wet stripes means it is partially clogged. You should not be overheating under normal circumstances.

Have you checked the thermostat? DPOs have sometimes removed them in an attempt to cure overheating. Removing it will make things worse due to the design of the cooling system.

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Joachim

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 Posted: 03-30-2015 06:32 pm
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Esprit2
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Oil viscosities are ranges, not values (SAE 50 = 900-1300 Saybolt Universal Seconds at 100 F). It's possible for one 50wt oil to be at the top of the range, and another to be at the bottom of the range, and both are classed as 50wt oils.

In a 20W50 viscosity, the 20W indicates the oil's viscosity when cold (0 F), and the 50 is it's viscosity when hot (100 F). When selecting an oil for your 907, it's important to keep the second number at 50 or above, and 20W-50 is the default spec (BMW's house brand 10W60 oil for their 'M' series engines is excellent, but expensive).

If you live in a cold climate (real arctic cold, not southern chill), and actually drive the car in cold weather, then dropping the 20W part of the viscosity to 10W or 5W will help the engine start more easily on a cold morning. But once the engine is up to temp, it's the 50 part that counts, and the __W part is no longer relevant.

There are different approaches to bearing and lubrication design. Most modern engines that must meet mandated CAFE standards (Corporate Average Fuel Economy) are using lighter and lighter oils, which then require tighter and tighter bearing clearances and higher oil pressure. It's a 'complete', inter-related design package. Using a thicker viscosity oil in those engines does not work.

All Lotus engines prior to the recent Toyota powered models (all 9XX 4-cyl, Lotus-Ford Twin Cam, Coventry-Climax, etc) use bearing/ lubrication designs that are at the opposite end of the spectrum. The oil of choice has a relatively high viscosity at normal operating temperatures. That requires more open bearing clearances along with a lower oil pressure, but with a high flow rate.

Many owners of vintage cars & older Lotus seem to think that since their modern car is using a 0W20 or lighter oil and the engine lasts a long time, that oil must also be better for their (insert vintage Marque) engine. NO, that's not true! The new Honda is designed and manufactured for water-thin oil, and the 907 was not. Don't try to force either one to be what it's not.

Each engine is a complete design package, each needs what it needs, and the 907 needs a 50+ viscosity oil at normal operating temperature (ie, when hot). 10W40, 10W30, 5W30, and lighter modern oils are NOT better for it regardless of what an overzealous oil company tech rep will tell you, will lead to excessively low oil pressure, and possibly rod-knock. Do not go there.

*~*~*
The 907 is also a flat-tappet cam design that uses pretty ordinary metallurgy. It depends upon extreme pressure / anti-wear additives in the oil to keep wear in check. Keep the phosphorous level up (the P in ZDDP). The Z and the P are not present in equal balance, and an oil with 1300 ppm of ZDDP will have about 1200 ppm of phosphorus... which is the minimum you should run in your 907. The Valvoline VR1 oil mentioned earlier is in that ZDDP range.

The old Mobil 1 20W50 that Lotus recommended contains more ZDDP than the API now allows for automotive use (more than VR1), so it has been re-branded as Mobil 1 20W50 V-Twin Motorcycle Oil. It's still the same great stuff, you just need to shop for it in the motorcycle aisle.

Most modern oils are lower in ZDDP than what should be used in the 907. Even oils that claim to be 'Added ZDDP' are only 'added' relative to the super low level to which they cut it back a few years ago. They took a lot away, put a little back in, and claim 'Added ZDDP'. BS, don't fall for it.

You want 1200 ppm phosphorus (1300 ppm ZDDP) minimum in your 907 (ie, the current API SN maximum) or more. More can be had via certain select motorcycle oils, or certain racing oils.

Some oil companies blend oils with more ZDDP than the API allows, then market it as non-certified racing oil 'for off road use only' (WWNNSNM - Monty Python). I call them boutique racing oils. They still have all the anti-sludge, detergent and other additives a long change interval street oil requires, but with a high level of ZDDP. They're safe for extended drain intervals in street use. Valvoline VR1 (NOT VR1 NSL), Mobil 1 Racing Oil, Redline Racing Oil, Castrol Racing Oil, and others are examples of those boutique racing oils.

A real racing oil is an 'event' oil. It only stays in the engine for one race event, and is changed afterward. It doesn't need the street additive package, so it doesn't have it. If you use a 'real' racing oil, then change it every 500 miles or 3 months, which ever comes first.

At levels above 1500 ppm, phosphorus becomes corrosive to the metals used in engines. Long term, it can be bad, but the parts don't immediately dissolve. Wear can be bad as well, and the high wear rate that can occur with insufficient ZDDP is worse than the glacial rate of corrosive attack due to too much. You might be wise to save the really high ZDDP racing oils (2400 ppm) for track days, but there's no reason to shy away from a 1750 ppm Mobil 1 for general street use. It has a history of everyday use for decades.

A few current motor oils with high ZDDP levels:

.Phos. / Zinc
2400p / 2500z Redline Racing Motor Oils (Typical, “all have a min. of 2200 ppm Phos” - contains full street additive package)

1750p / 1850z Mobil 1 0W-50 Racing Oil (contains full street additive package).


1600p / 1700z Mobil 1 20W-50 -- old, discontinued,
..................... now Mobil 1 20W-50 V-Twin Motorcycle Oil

1600p / 1700z Classic Car Motor Oil -- http://classiccarmotoroil.com/

1200p / ......... API SF (1980-88) permitted the highest ZDDP levels ever API-specifed,
1500p / ......... with phosphorus ranging from 0.12% to 0.15% (1200-1500ppm).

1400p / 1500z Brad Penn®, Penn Grade 1 Hi-Perf mineral oils

1300p / 1400z Valvoline VR1 Racing Oil ('boutique racing', has street additives, made in full synthetic & mineral oil versions... read the label), API SF/CD.

1300p / 1400z Valvoline VR1 NSL "Not Street Legal" Racing Oil, NO street additives, change every 3 months/ 500 miles.

1200p / 1300z Mobil 1 15W-50 (vintage flat-tappet engines/ Lotus approved).

1200p / 1300z API SL/ SM/ SN “allows” but does not mandate 1200p for SAE 40 and heavier oils. Lighter viscosity grades are restricted to less ZDDP.

Last edited on 03-31-2015 01:21 am by Esprit2

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 Posted: 03-31-2015 01:53 am
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Esprit2
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rday wrote:
Thanks All,
   Your comment on a lighter viscosity oil affecting engine temperature makes me wonder if this is why the engine runs hot.  Around town I have no problems, but any distance under load (up long hills) and on the highway (60 mph +) it does get hot.  I thought maybe that the radiator was partially plugged or it may need a new thermostat.
(Snip)...
I was also planning on flushing the cooling system again and replacing the thermostat.  Any other suggestions?
A light oil viscosity might affect engine temperature, but I wouldn't bump it up to the top of the list.

Check the air-fuel ratio. It's reasonable to assume that the carbs might be a little dirty after decades of use and modern alcohol blended fuel. The Federal Stromberg 907 is emissions-lean to begin with, and a dirty jet and/or needle will further restrict the fuel flow, and make a lean condition worse. And lean will run hot.

It's also reasonable to presume the radiator isn't as clean as it once was, and that the thermostat isn't working as it should. The t-stat is easy to change, just select one with a low temp rating (~78 C). The radiator is harder to clean out, but do address it.

The early 907 water pump (all J-H ?) use an impeller with forward curved vanes, small vanes, and not many vanes. It didn't move enough coolant, and was prone to cavitation at higher rpm. Later Lotus 907 water pumps used rearward curved vanes, and more of them. Those impellers are a direct fit into a J-H pump, move more coolant, and never cavitate.

Finally, the 910 Turbo pump uses the best impeller and moves the most coolant. It's impeller's nose is too long to fit in the early 907 pump's housing, but you can have a machine shop shorten it to match the overall length of the early 907 impeller. With that done, re-assemble the pump as usual. The upgraded pump will circulate significantly more coolant, and be a big help with keeping the temps under control. The 910 pump moves the most coolant, and the shortened 910 impeller in the small 907 housing will produce about 90% of the benefit of installing a full 910 pump.

Overheating under load also indicates a possible head gasket problem. Have a hot compression test and a leak down test performed to determine if there's a problem.

Do the compression test with the throttle held wide open, and the engine cranking at 200 rpm minimum (it helps to remove the spark plugs from the cylinders that are not being tested. Jensen-Healey specified a cold test, and pressures of 110-130 psi, cold. Lotus specified a hot test after the engine has been warmed to full operating temperature, and pressures of 150-170 psi hot.

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 Posted: 04-02-2015 12:57 am
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rday
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This information is great, thanks to all.  My JH is a 1974 five speed so I can only assume it has a "newer" water pump in it.  The water pump was also replaced very recently.  The last compression check done was a cold test and I believe all cylinders were around 120 or so.  I have a large folder filled with service information on this car back to the early 1990's.  Many major repairs were completed including clutch, suspension, Head R&R, new driveshaft, electronic ignition, exhaust and more.  I have no mention of any carb work though.  It runs well most of the time and the sputtering while running the RPM up through the gears occurs only once and a while.   I thought it  could be rust in the gas tank that is intermittently clogging the pick up screen in the tank.  My father, the previous owner, has told me that the filters seem to get quite dirty. It does seem to idle a bit rough, but not so rough as to stall.  I have worked on many carbs over the years but mainly U.S. makes such as simple Rochesters.  Is there a good way to test them on the car?  As far as the radiator is concerned, can a plugged radiator be cleaned or is a new radiator in my future if this is what it is.  
    

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 Posted: 08-02-2016 12:44 am
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redracer
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almost all the overheating problems, especially in the post '73 engines(took an extra 2 1/2 quarts of oil which helped cool them) and the pre '75 engines with their much larger radiators, were from the radiators.(My original is like yours, a '74 5 spd). We used to put 4 rows in the tanks(the top and bottom part of the original radiators) which took care of this problem, but they are no longer available, at least here. Originally, we tried a 3 row where the tubes were lined up(front-to-back) but this helped only slightly. However, the 3 row STAGGERED radiators take are of this problem. Of more recent note, many have put the CHAMPION aluminum radiators in, which appear to solve our problems plus are much cheaper(very reasonably priced) than the copper cored ones. I would suggest changing this rather than cleaning your old one.

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 Posted: 08-02-2016 01:38 am
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rday
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I had the radiator cleaned last summer and that solved the problem.  This summer thought, The gauge creeps up if it is very hot and I am going up some hills.  I recently had to replace a needle valve in one of the carbs.  Could one of the carbs being slightly out of tune cause this issue?

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 Posted: 08-02-2016 02:28 pm
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redracer
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Yes, as ESPRIT2 pointed out, a lean carb. can make the engine run hot. Please get a CO meter, colortune, or whatever to check your air to fuel mixture. Again, as previously pointed out, the cars originally came to the states quite lean. I have a CO meter and tune it to 4% or slightly higher at 2800-3000rpm. I don't know if your state still has emission laws for older cars like ours, but in Georgia there is a 25 year rule, which would have been 1999 for us.

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