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rgh0

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  1. Most synthetic and mineral base oils actually tend to cause rubber seals to shrink so appropriate rubber swell additives are added as part of the formulation in quality oils to counteract this.  "High mileage" engine oils or supplementary lubricant additives have additional swell additives to help counter wear on seals by additional swell to minimise leakage from places like the rear main seal 

     

    cheers

    Rohan

    • Like 1
  2. You can work out the original design valve stem install height as follows if you have a bit of time and some measuring tools.

    Valve tip must be the following distance from the cam centreline

    standard cam base circle radius + design clearance ( say 0.010") + follower thickness ( std is 0.220") + standard shim (nominal 0.120")

    You can then measure cam centreline to spring pocket base buy measuring the cam carrier depth to cam centreline and spring pocket base below cam carrier mounting face

    You can then calculate how much spring stem tip  needs to be above the spring pocket base when setting the valves in the head.

     

    If fitting a high lift cam then you may need a smaller cam base circle and longer valve stems and thinner follower to fit in a suitable spring that is 0.060 away from bind at full lift 

     

    cheers

    Rohan

     

  3. I would measure up the followers and carrier for wear. if its all within the factory specs then it does not matter which goes in which location. You need to measure top middle and bottom of the follower and carrier as the follower wears in a barrel shape and the carrier in a hourglass shape. 

    The other issue can be wear on the follower top to cam  so check the cam lobes and follower for any signs of wear also. 

     

    In the end a new set of followers is not that expensive  if you find enough wear to give concerns about reassembly in different locations

     

    cheers

    Rohan

  4. The thinner followers are typically needed when using high lift cams that have both a smaller base circle to keep the lobe tip radius acceptable but also to enable a longer valve stem and larger valve tip height and long valve spring that can accommodate the higher lift.  

    Of course the thinner follower can also be used to hide bodges with valve seat over cutting or reground cams.

    I deal with this when building competition twin cams for my Elan and have a design spreadsheet to manage all the variables. One day I will set up a similar design spread sheet for the 9xx engines when I finally get around to building a big engine for my S1 Esprit :) but so far the original engine keeps working.

    cheers

    Rohan

     

    • Like 1
  5. I understand how the regulator adjustment works to hold the fuel pressure above the carb pressure and that the regulator will "try" to hold a constant fuel discharge pressure relative to atmospheric pressure if the sensor hose is disconnected.  

    As the throttle opening increases and the boost increases the pressure in the carb bowl increases.  This means less fuel will be delivered as the back pressure on the float valve increases and the float has to drop to deliver the required fuel. The lower fuel level will lean out the engine leading to loss of power.

    The fuel regulator is a simple proportional controller and its delivery pressure will increase with increasing fuel back pressure due to increasing carb pressure if the reference pressure line is disconnected

    There are multiple influences fighting each other  here but the end result is a lower fuel level in the carbs and the engine running lean and loosing power.  Connect the sensor tube to the plenum and assuming everything else is correct it will work. Unfortunately the odds of everything else being correct are not that great

     

    cheers

    Rohan

     

    • Like 1
  6. 19 hours ago, TRLOTUS said:

    Thanks guys!

    Fuel pump operation had been my first check. Looks correct.

    I did the fuel pressure check today. The regulator had been set for 3.2 psi at engine out of operation, 3.5 psi at idle and the pressure increased in approx. to boost pressure increase. Than I changed the pressure regulator setting. I recognized that somebody changed the setting in the past and original position had been at 4 psi. Therefore I set 4 psi and tried to drive the car. I recognized that the engine operation is  much more better, but the problem persists. Next step had been regulator change to 4.5 psi. The engine operation had been better again, but the problem persists. But I recognized that the low speed engine operation is a little unstable now.

    From my point of view somebody has had trouble with engine operation in the past. He did not find the correct failure and tried to repair the engine by decreasing the fuel pressure. Maybe the engine operation had been close to correct. But the real failre persists. Probably there is not one trouble only. My idea is to replace fuel pressure regulator, to do deep carbs check and electric system check.

    with the fuel pressure regulator boost pressure sensor disconnected fuel  pressure will increase with boost due to the increased back pressure but it will not stay the required amount ABOVE the boost pressure leading to problems.  if this is wrong there may be other major things wrong with the pressurized carb set up that cant easily be seen from your photos.  if you dont understand how pressurised carbs with blow through turbo works then find someone who does, as lots of little issues of not properly sealing the carbs and all their connections can give you a problem.

     

    cheers

    Rohan

  7. Just a note of caution.  After not driving my S1 Esprit for a few to many months due to Covid lockdowns I finally had a chance to drive it last weekend

    The car started fine but then immediately started to run on only 2 cylinders so I turned it off to investigate.  When I got out there was a large pool of petrol spreading under the engine !!!! Luckily I could push the car away and mop up the petrol without incident

    Investigations showed that the front Dellorto was flooding with fuel coming out the trumpets soon after the ignition turned on the fuel pump.  It was a relatively easy fix by just removing the carb top cover and cleaning the float valve and ensuring everything was moving smoothly.  I could see nothing wrong that could have cause the flooding and presume the float valve jammed open due to sitting for too long with the fuel evaporated out of the carb bowls.

    After the carb fix the car needed new plugs and then ran rough until I filled it will fresh fuel.   It bought many smiles to be able to drive it again :)

     

    cheers

    Rohan

     

     

     

     

     

     

  8.  

    Race tow arrangements on a Lotus with the fibreglass bodies always a challenge !

    For my S1 Esprit I use a light steel rod bent in a triangle shape from the two front lower suspension pivots. It sits under the cooling intake moulding on my S1 to provide a centre tow point at the front.  At the rear i have used a steel cable from a lower bolt for the lower pivot on the RH side lower suspension link to provide a tow point loop on the end of the cable tied with a wire to the exhaust . If its used and pulled sideways the tie wire will brake and the tow cable move as needed.

    Never needed on my S1 Esprit but a similar arrangement used more than once on my Elan :)

     

    cheers

    Rohan

     

    • Thanks 1
  9. I have a couple of 2 litre 907 engines from  78 and 79 Esprits and a later 912 2.2 litre from a early 80's front engined car either Excel or Eclat.  The basic block castings look the same though there may be some minor machining drilling and tapping difference depending on the original application. The major difference with the 912 block was the beefier ladder bearing carrier and sump casting but the block itself appears to be the same as the earlier 2 litre 907

    The earlier 70's rope seal blocks in the Jensen Healys may have been different  as Lotus is supposed to have updated the block due to liner reliability problems according to wikipedia ??

  10. The OEMs moves to HTD belts were to achieve the lower noise and longer wear life of the round tooth belt and pulleys profile.  Unless you doing high miles and want a car where you cant hear that lovely belt whine at 7000 rpm behind your head stick with what you have got IMHO.

     

    Provided installed correctly and maintained right the trapezoidal belt profile is no worse at jumping teeth than the HTD belt, Millions of cars and many millions of miles point to that again just IMHO

     

    cheers

    Rohan

    • Like 1
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