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Oil Pressure Relief Valve  Rating:  Rating
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 Posted: 02-01-2007 04:08 am
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Dan Eiland
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I am in the process of rebuilding and upgrading my JH engine and was
wondering if someone happens to know when Lotus switched from the old sleeve
style oil relief valve to the newer spring ball check valve style oil relief
valve? I plan to tear down the oil pump and rebuild and check all the
clearances to see if they are within spec, so I know I will find out what
type I have at this point. Just wondering if there was an engine number or
date that determined when the switch took place? Does someone have a picture or drawing of the newer style relief valve? I see the old on in the JH parts book, but no mention of the change to the newer style.

Last edited on 02-01-2007 04:09 am by Dan Eiland

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 Posted: 02-05-2007 12:13 am
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Dan Eiland
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I pulled apart one of my auxilliary housings and did not find a ball style check valve so I guess I have the plunger type. The hole is visible inside so the sleeve has not moved down and covered the hole. I measured the thickness of the original gasket and it measures 0.007 inch. I got out the new gasket from my gasket kit and it also measures 0,007 inch. I would think it would be prudent to install a slightly thinner gasket if I reuse all the parts. Everything looks in very good condition. Is there any reason to change out the parts if everything is in good shape. I was thinking of getting a gasket that is 0.006" or 0.005" and see if everything still works good. I can get several different size gaskets and see what works best. I can start with the 0.007" and if my oil pressure is too low go to a smaller size and see if that helps. How can I tell what is correct without all the guesswork? 

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 Posted: 02-05-2007 03:16 am
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Mark Rosenbaum
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AFAIK, while there's an o-ring in the closing cap, there is no gasket involved in the oil pressure relief valve itself.

If the gasket you're talking about looks like the one in the attached photo, that's the special plastic gasket that sits between the aux. housing and oil pump body.  These were made in several thicknesses so that one can set the total clearance between the oil pump rotors and the castings to the specification, which is 0.000,5" to 0.001,5".  That's a critical dimension.  Too small, the pump rotors won't turn and you may snap a timing belt upon initial turnover.  Too large, and the oil pump will not self-prime and may even quit without prior notice during engine operation.

Attachment: oil pump gasket A907E0474Z enlarged.jpg (Downloaded 229 times)

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 Posted: 02-05-2007 04:49 am
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Dan Eiland
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Hi Mark, the gasket you show is the one I am referring to and I apologize if it sounded like I was referring to the relief valve having a gasket. I need to clean all the parts and then I can begin working with clean parts. I was just reading some of the past posts to the board about this subject. I think I am starting to understand how to measure some of these clearances but not all of them. I can understand using a straight edge and a feeler gauge to check the clearance from the rotors to the housing. I liked Judsons method of having a collection of gasket sizes on hand and dry fitting them until you have just the right amount of movement. I'm still not clear how to check the clearance between the inner and outer rotors, or the clearance between the outer rotor and the housing. I'm not clear as to how or what methods to use for these measurements.

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 Posted: 02-05-2007 01:56 pm
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Mark Rosenbaum
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To check rotor to rotor clearances, you can use a Plastigauge or a gauge using wires of various thicknesses (like a spark plug gap gauge).  For rotor rim to housing clearance, I don't see any obvious way to use Plastigauge, but the wire gauge remains a good choice.  For both measurements, a blade type thickness gauge can also work, though perhaps with slightly less accuracy, if its blades are flexible enough.

The club store sells Plastigauge, as do many of the larger auto parts stores.  A good wire thickness gauge for clearances less than those normally found with spark plugs and ignition points may be a bit harder to locate.  It's also possible to take a length of brass or steel wire, sand or stone or file its end down until it just fits a gap, then measure the end's thickness with a micromenter.  For long-lived hand-made gauges of that sort, spring wire or music wire is often a good starting material. 

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 Posted: 02-05-2007 03:00 pm
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Dan Eiland
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Mark, I will check with some of our industrial tool suppliers and see what they have available for this. If I can not find a tool I will resort to making something. I could get different thicknesses of gaskets and use them to measure the clearances. Since the oil pump gaskets come in different thicknesses I thought I might purchase a set starting with the smallest ones up to what I already have and I could use them to check these other clearances. What are your thoughts.

Last edited on 02-05-2007 03:01 pm by Dan Eiland

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 Posted: 02-05-2007 04:47 pm
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Mark Rosenbaum
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Oil pump gaskets are supposed to be available in several thicknesses.  According to the parts book, these are:
JH P/N 94097 - Lotus P/N unknown - 0.001,5" thick - color red      
JH P/N 94098 - Lotus P/N unknown - 0.002,0" thick - color yellow
JH P/N 94099 - Lotus P/N unknown - 0.003,0" thick - color royal blue
JH P/N 94100 - Lotus P/N unknown - 0.004,0" thick - color black

Furthermore, under P/N 93545, Delta supplies a red gasket associated with Lotus P/N A907E0474Z.  Somewhere along the way I gathered the impression that this was the only gasket still available -- but of course I could be wrong.  All of the gaskets I've actually seen have been red and very slightly more than 0.004,0" thick.  This includes the one in my car's engine when I bought it (known to be a replacement at some time in the car's past), the one in the engine I bought from Kurt Housh, and all of the ones I've ordered from Delta over the years.

To further confuse the issue: while looking into this, I found that Lotus has changed several critical oil pump specs.  Comparing the JH shop manual to an unnumbered Lotus tech data pamphlet datestamped April 1987, we have:
Clearance between tips of rotor (inner gear) and annulus (outer gear): JH 0.006" max; Lotus 0.002" min, 0.006" max.
Annulus end float: JH 0.000,5" min, 0.001,5" max; Lotus 0.001" min, 0.003" max.
Rotor end float: JH 0.000,5" min, 0.001,5" max; Lotus 0.002,5" min, 0.003,5: max.
Annulus rim to housing clearance: JH 0.001" min, 0.003" max; Lotus 0.007" min, 0.012" max.

In this regard I'll note that most of the rotor gears I've seen were very slightly thinner than the annulus gears, and the Lotus rotor end float spec may be nothing more than official recognition of this situation.  The Lotus annulus end float seems a bit high to me, and I'd be worried about pump priming in a well worn engine.  I don't know wny the annulus rim to housing clearance specification was changed so much, but it's been my experience that it isn't a particularly critical dimension.  Others with greater experience in these areas may well have different opinions. 

Since no rotor and annulus part numbers are provided, it seems reasonable to expect these revised specs to apply to the JH too -- certainly if any parts have been replaced with non-vintage ones.  With that in mind, I'll note that Lotus also revised the minimum oil pressure spec (hot engine) as follows:
Idle, 5 psi minimum; 3500 rpm, 35 psi minimum; 6500 rpm, 45 psi minimum.

I guess this means that if you have 45 psi at 6500 rpm, the engine will survive the warranty period.  After that...?

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 Posted: 02-05-2007 07:42 pm
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Judson Manning
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Dan,

If you don't have one already, get a set of feeler gauges at one of the better auto supply places.  My set is basically a grouping 1/2" wide by 3" long pieces of sheet-metal .002" all the way to .030" in thickness. 

This tool is indespensible when it comes to shimming valves.  In like fashion, assemble the inner and outer pump rotors on a flat surface, then insert your feeler gauge between the rotor lobes. 

When new the gap between the rotors should be roughly .0045" and never more than .006".  I have seen pumps with as much as .012" that pumped oil, but took 30sec to prime and never exceeded 50psi hot.

Don't concern yourself too much with the outer rotor to body clearance, while critical, it usually isn't an area for wear.  Just put the rotor in the body and move it by hand to see how far it moves - use your best judgement.  Given my bad experience with rotor-to-rotor clearance, I would highly suggest buying a new set of oil pump rotors.

Also, when you rebuild the pressure regulator, install a small nut (similar to a #10) on top of the spring to compress it 3-4mm.  This will bump your pressure from 60psi to about 75psi.  Max is about 6-7mm which will cause oil to start coming out the seals.

Judson

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 Posted: 02-06-2007 05:33 am
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Dan Eiland
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This is where I'm at with this issue--I went out and purchased a blade style feeler gauge that starts at 0.0015", 0.002", 0.0025", 0.003", 0.004" and so on. I used this gauge to measure the Annulus (outer Gear) to housing clearance and was able to get the 0.004" blade in but the Annulus would not turn. When I place the 0.003" blade between the pieces the Annulus will still turn but is snug. I'm not clear if this means the clearance is 0.003" or 0.004", but at least I can report something to the list.

Next I placed the annulus and rotor into the housing without being on the shaft. I measured the clearance between the lobes and was able to get the 0.007" blade between the lobes but not the 0.008" blade.

I have not measured the clearance where the gasket fits but the new gasket seems to measure 0.005" yet it is black in color and came out of the gasket kit. I have now measured the thickness of two old gaskets and they are both 0.005" as well. Both my oil pumps use the sleeve style pressure relief valve and both look in good condition. Had not planned to remove these---should I? 

Where do I go next? I guess I need to still measure the clearance where the gasket fits, but can anyone tell me if I really need to replace the rotor and annulus? Is there anything else I need to do with the oil pump/auxiliary housing?

Last edited on 02-06-2007 05:36 am by Dan Eiland

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 Posted: 02-06-2007 06:31 pm
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Jay
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While on the topic of the oil pump, I have some general questions.

First:
If I suspected that my oil pressure was not as high as recommend, at what point would disassembly and inspection of its internal components be advised? With that in mind, I wanted to know if the pump and housing can be removed, independent of the auxiliary drive shaft. In other words, just what components need to be removed to be able to remove the oil pump?

Second:
I thought that I read somewhere that the oil pump has a sort of one-way valve that is to prevent the oil from draining when not in operation and thus keep itself "primed". Is this so? If so, should it be able to hold back the oil for an extended period of time? I would assume that this is why it takes a degree of time (seconds) after start-up, for the pressure to build, but I would also think that some of this time could be attributed to the transfer of the oil through the engine.

Third:
I have read of some sort of oilier system that can pre-oil the engine prior to start-up. Where can I get more information on such a system? Just as a thought, I was wondering if has anyone has considered or herd of some sort of oil reservoir, located somewhere above the engine block, that could act as a feed to insure that the oil pump is primed by gravity?

Just gathering general knowledge. I appreciate any of your thoughts and advice.

Thanks, Jay

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 Posted: 02-07-2007 03:14 am
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Judson Manning
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Jay,

There was a lot about the early 907 variant's oiling system that wasn't desirable, and revisions were made all the way to 1995.  If your engine takes more than about 5-10sec to build pressure, chances are the pump rotors are worn.  If you have a VERY early engine, it may never have gotten the air-bleed hole added to the accessory housing.

The anti-drain-back valve is a feature found on Lotus and a few after-market supplied oil filters.  That filter and the air bleed hole added to the accessory housing in 1974 was a HUGE improvement to the MkI engines. 

The 'defect' if you want to call it that, is the pump being mounted 12" above the pick-up.  The first Esprit Turbo (or is that Turbo Esprit???) was supplied with a factory dry-sump set-up to eliminate the priming issue.  As the oiling system evolved in the later 910 variants, Lotus dropped the dry-sump.

Racers are a great believer in the Accusump when the rules don't allow a dry-sump set-up.  On the JH, the Accusump gives the added benefit of pre-oiling the engine while the pump primes.  For more info:  http://www.accusump.com.

Judson

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 Posted: 03-04-2007 05:17 am
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Dan Eiland
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I decided to pull apart my original auxilliary housing today and check all the tolerances. If I did not know better I would think the rotor and anulus were new. All measurements are well within spec. After cleaning the housing I installed a new oil seal then used engine assembly lube with moly-graphite on the shaft and also placed a very small amount on the rotor and anulus. Now I am wondering if this is correct? Should I have used engine assembly lube on these parts or should I have used engine oil? I was thinking of using Mobil 1EP 15W50 in the engine once I'm done and thought that I should have used this to lube the oil pump parts on reassembly. Just wondering what others have done. Your feedback is always appreciated.

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 Posted: 03-04-2007 02:11 pm
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Mark Rosenbaum
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When I fixed my car's oil pump some five or six years ago, I used 10w40 motor oil to lube the various surfaces, anti-sieze on the bolt threads, and a thin film of Loctite 515 on the sealing surfaces of the oil pump to aux. housing gasket.  Since then, there have been no leaks, quick priming (3-6 seconds, depending), good oil pressure both hot and cold, and no oil pressure problems of any sort.

Of course, since I haven't stripped things down to check on any hypothetical added wear, I can't say if an assembly lube would have prevented any such hypothetical added wear.  I'd expect that it might, but on a daily driver, I doubt there's any reason for concern.  On a race car, though, it might be more important.  Does anyone know what Lotus recommended, at the end?

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 Posted: 03-04-2007 04:28 pm
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Dan Eiland
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I find it interesting that there is no mention in my JH Manual or Lotus Manual of lubricating any of the moving parts inside the oil pump on the rebuild procedure. I would think that one would lubricate the shaft and the rotors with either engine assembly lube or engine oil. My concern is with the tolerances being so close (i.e. 0.0005 in some cases) that engine assembly lube may be too thick and cause some issues upon assembly such as the rotor and anulus being too tight. Once oil is drawn into the pump this may no longer be an issue. My guess is that either will work just fine and will adequately protect the parts upon startup until the pump primes and fills with engine oil. I just got to thinking after I had applied the engine assembly lube and reassembled the pump that it would have been better to use my engine oil for this since that is what will be lubricating these parts once the engine is running again. If one thinks about the main bearings and the fact that one uses engine assembly lube in this area then I would guess it is safe to use it in the oil pump.

NOTE: One change between my JH Manual and my Lotus Manual applies to the oil pump gasket. My JH Manual says to "Apply a suitable jointing compound to both faces of the new gasket fitted between the oil pump body and the auxiliary housing," where my Lotus Manual says, " Fit the oil pump to the auxiliary housing using a NEW gasket which is fitted DRY."

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 Posted: 03-04-2007 10:33 pm
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jensnhealy
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I hesitate to weigh in because it has been so long and I don't recall who gave me the advice. When I was ready to start up a rebuilt 907 years back, I wanted to have oil pressure before I tried to fire it, so I spun it with the ignition deactivated and couldn't get any oil pressure reading at all. Very disconcerting. Tried a bunch of things. Nothing.

Eventually, someone on either this list or the Lotus list advised the pump probably wasn't priming and to pack the inside of the oil pump with white grease (which would create a vacuum and prime the pump). Somewhat skeptically tried it and got immediate oil pressure. 10 years later the pressure was still good, so I have to say it worked like a champ.

Just someting to keep in mind if your pressure doesn't come up as it should.

Scott

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