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mad_wolf

Elite with 907 Type B Motor

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It looks like that my Lotus  cars are all a bit non standard.

As I started to build up my 1974 Elite I realised that the Motor differs to my other motors.

It has a B number - where were these Motors original build in ?

It has adjustable camshaft wheels - do someone know the producer of these or has information about efforts of changing the Timing ?

It has 2 double SOLEX carburettors - I know already that they where originally used by Lotus. But is there any System behind it ?

Is there any documentation to this motor typ usfull for MOT / German TÜV ?

907 B.jpg

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Jensen Healy motor?

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Yes could be but is normaly a Type A motor

And it has original Lotus Cam covers instead of JensenHealey covers.

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Yes, I actually have an A motor in my 501 in Aus, well, at least the bottom end, it has dellortos and Lotus cam covers. But, I seem to recall an article on the web about development 907's and one was a B motor? It definitely sounds familiar. Good luck on the search.

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European and US market Jensen-Healeys had either B or T prefix 907 engines and were fitted with Stromberg carbs

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In the Forum of the Jensen Owners Club is the following Information availible:

It's not listed as a Jensen engine number.

Thanks Richard. This is interesting. Lotus never used a single "B" prefix letter in their engine numbering, and their single or double letter prefix was always followed by the engine series i.e. 907 or 912. So B74026053 is definitely not a Lotus engine number. Assuming it was Lotus that stamped the engine number on the blocks prior to their delivery to Kelvin Way (as opposed to JML stamping blank engine blocks received from Hethel), is it possible that this engine block was removed from the production line at Hethel at some stage, and used by Lotus for other purposes?

And: B74026053. It is currently installed in a LHD 1976 Lotus Eclat 521, and seems to be a Team Lotus "engineer's special".

 

As I own also 2 Jensen Healey's one European and one from USA.

Both have 907 type A engines.

 

So I'm more confused now.

 

MotorNo.jpg

Camwheels.jpg

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I've seen some odd engine numbering in the register. Especially on early cars.

The presence of the variable cam timing wheels and non standard carbs suggests its a modified engine. You wouldn't fit verniers unless you needed to adjust valve timing as they can slip. (I have the remains of a "hot" 907 engine in my shed which died due to a slipped vernier pulley...

My guess - and it is just a guess, is that Lotus tried lots of different parts in their evaluations, and that when some were found to be not as good, or too expensive for inclusion on the production cars, the found their way onto employee's cars.

Either that, or an enthusiast has gotten hold of a block from a JH and built up a hot engine using solex DDH from an Alfa or suchlike. Are the Solex 40 DDH's? or 45's?

I'd bet those are fancy cams in that engine....

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I may be wrong but the cam sprockets look to be the later 'half moon' ones rather than the earlier 'square toothed' ones - the cam belt however looks like it should be for the earlier sprockets?

I know @clivef38 has a set of the later sprockets and an appropriate cam belt to suit so may be able to confirm?

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I agree - it does look like a square tooth belt on a half moon pulley. Has this engine ever been run? Or has it been laid up and then given a new belt? If so, I also think the belt might not be the right one.

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You are right it is the old and wrong belt, I do have a new one but this motor is running.

I just disconnected several things and did removed the intake manifold which was a good idea because

the middle water path was blocked by some crystalline and slime material.

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Dunc you asked for the size.

They are Solex 40.

 

i

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I have found a Youtube with a Jensen-Healey with 907 Motor with the same Cam wheels.

Its from 11.5.2017. This one has Dellortos on it but the person has some problems with colour.

There are more motors of this type in the world.

907 Cam Motor.jpg

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Motor does not rev above 4000rpm

 

I need some help because I'm running out of ideas and time:

 

I have a fine starting and idling motor.

When I open the throttle the motor follows slowly but above 2000 accelerates quick but does not goes over 4000rpm.

It revs up quik to 4000 not further like running against a wall.

I checked the following:

 

Ignition: Changed old Lucas to Bosch 3Ohm ignition coil, did make it better.

Alternator did had already a hall sensor electronic ignition.

But no vacuum so I assumed specification 3 for 907 motor.

I set the timing and the time shift to advanced works.

I checked the carburetors, cleaned all, changed to different sizes nozzles. Balanced it

Checked fuel level and made some variations.

But original setting was the best but I measure only 0.2% CO.

No smoke and no steam from the exaust.

Motor runs only fine with air filter on. Without I get only 3000rpm.

Idle is with or without air filter perfect.

Chokes work.

 

I checked the cam. They are both original non groove versions.

I varied the cam timing but original setting was the best.

The motor has fresh synthetic oil and all test were performed at 90°C water temperature.

I sprayed around the carburetors with break cleaner → no change so no leak.

Intake manifold and carbs have new sealing.

 

What could be the reason that this motor does no run as Chapman did designed it to rev like a real Lotus ?

 

 

 

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14 hours ago, mad_wolf said:

But original setting was the best but I measure only 0.2% CO.

That sounds unfeasibly low for an older car on carbs.   I would be looking for a fuel delivery issue.   Feed from tank?  Fuel pump?

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= lack of fuel.

check the pump is earthed and pumping hard, fuel filters, carb float height (critical on a 907) then jets for blockage.

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Sorry I forgot that I can flood a swimming pool with the fuel pump.

And I can hear by he tick the amount it is actual pumping.

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The bowls hold enough fuel to allow full throttle for a few seconds from tickover, so fuel supply won't be an issue. The sudden wall at 4000rpms suggests carb main jets (are both, air and fuel jets both present and clear on the emulsion tubes), but more likely to be accelerator pump circuit related, either the linkage the pump jets or the usual culprit is the diaphragms which perish.

 

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Dear Steve V8,

I changed already the main jets, not jet the air jets.

As I described: bigger jets gives 2000rpm smaller 4000.

Do you think the air jets make such a strong differenc and if should I take bigger or smaller ones ?

 

For the accelerator pump I think it is only adding fuel while openning the throttle.

So with opened throttle maybe slowly but it should go over 4000 or am I  wrong ?

 

 

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@Robbie posted this on my Elite Resto thread - do you have a similar issue with the rotor arm (can it be that simple?)

Posted March 27 (edited)

"Hi when you get o the distributor can you check whether you have a rev limiting rotar. My 1979 503 has a lucas rotar limited to 3500 rpm and I am not sure this is standard for  an. elite . The rotar arm is easily  identifiable as circular with half circle steel grounding plate marked on steel 3500 rpm. Thanks"

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Dear oilmagnet477,

I have a tiny normal rotor arm inside. So no rev limiter.

But what does a rev limiter in your 503 ?

I have checked the ignition with stroboscop and with oszilloscope. The spark is stable as a clock at any rev.

Next step will be to build in Stromberg's. You might imagine how much I'm desperately helpless I am.

 

 

 

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plugs are black. I also do not understand why my CO is so low (not CO2)

The black plugs is because of all the trials I do. There is no long run.

I will install Strombergs. I do not like them but then I might be able do seperate whether it is a carburator problem or not.

 

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Are you sure the distributor advance mechanism operating correctly? I've heard of situations where a screw in the baseplate stops full centrifugal advance movement and this can cause the problem you describe, especially if it feels as though you are losing power as you approach 4000 rpm.

Richard

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Yes I checked that with the stoboskop lamp. 

What I can not see it whether it would go to more advande behind 4000.

I'm think of making a home made distributer test device to check this.

Spec 3 is the most advance I ever havve seen on a Motor.

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1 hour ago, mad_wolf said:

Yes I checked that with the stoboskop lamp. 

What I can not see it whether it would go to more advande behind 4000.

I'm think of making a home made distributer test device to check this.

Spec 3 is the most advance I ever havve seen on a Motor.

The maximum centrifugal advance on Spec 3 is 32 degrees at 3000 rpm with no further advance beyond that. Timing at idle is also high at 16 degrees advance.  If the advance is artificially limited at say 2000 rpm, then you'd only get 24 degrees which would have the effect of progressively limiting power further up the rev range. Does your stroboscope show advance increasing up to 3000 rpm according to specification?

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