Lotus Elan

Clutch and pistons

PostPost by: thanatoid1 » Thu May 29, 2008 6:51 pm

Hi Guys,

I recently had to get my elan s4 ready for MOT and found a small job need doing first, The water pump had died over the winter!
Needless to say as I have not done any work on the engine since I bought the car 3 years ago I decided to do a full rebuild of the motor while it is out.
The problems I have (at the moment) are:
1). can I use a clutch driven plate that does not have a platen on a 4 speed gearbox?(with the right thrust bearing of course)
2). I want to put new rings on the pistons just for peace of mind but cannot find what size oversize they are. If I measure the piston the size is 82.89mm at the crown and 83.45 at the skirt, does this mean the piston is 40 thou oversize? (I presume the measurement should be taken at the skirt).
All help will be greatly appreciated as I do want to get at least some use of the car before summer is over!
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PostPost by: Petter Hval » Thu May 29, 2008 9:59 pm

Just clean the carbon of the top of the pistons, the size
should be stamped into the top surface, std for standard
or 0,xxx for the oversize.
Last edited by Petter Hval on Thu May 29, 2008 10:05 pm, edited 1 time in total.
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PostPost by: neilsjuke » Thu May 29, 2008 10:00 pm

You measure the pistons at the skirt 90 degres to the gudgeon pin .
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PostPost by: 1964 S1 » Fri May 30, 2008 3:33 am

Your water pump had died?
What is the clutch question about?
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PostPost by: types26/36 » Fri May 30, 2008 7:09 am

Hi James, how are you? Your question is a little unclear but I think you are asking if you can use the pressure plate that does not have the smaller plate in the centre (5 speed type)
Yes it can be used but as you say you will need the release bearing with the "rounded face" as the 4 speed type has a flat face.
I did this on my S2 many years ago but I cant remember if I had to change or modify the thrust bearing carrier.
As others have said you can measure the piston across the bottom but you can also measure across the bore at the top and it can be done with a vernier.
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PostPost by: thanatoid1 » Fri May 30, 2008 1:52 pm

Thanks for the replies guys,
Sorry my posting was a little unclear.
What I meant was that although I have to replace the waterpump (which I have no problem with) I also want to replace the bearings, rings and clutch while the engine is out.
The replacement clutch I have does not have a platen and I wanted to know if I could still use this on a 4 speed box.
The second part of my query was that I could not see what oversize the pistons where and was wondering how to find this out.
Thanks to your advice both problems have bee solved.
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