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Mk 1 with a better crank/seal  Rating:  Rating
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 Posted: 01-04-2013 10:52 pm
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roverman
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First off,does the Mk II engine have a non-rope rear main seal ? Starting what year ? I am securing a raw forged crank,(stroker potential), for retrofit to the MkI, and later engines., using the Viton rear seal. Various stroke potentials are likely and a balanced rotating assembly,(kit), is the goal. Discussion ? Thanks, roverman.

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 Posted: 01-05-2013 12:15 am
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Art DeKneef
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The Mark II engine uses a regular rear main seal, not the rope seal. The year would be 74 but with some things Jensen it is the engine number you need to check. Earlier engines didn't have the oil filler cap on the valve covers but up on the firewall. And I think it was engine 2760 and earlier?
 
For the crank I think it is going to come down to the owners desire for an engine upgrade and cost.
 
A lot of us I believe would like to do an engine upgrade but then don't because of the cost of a "good" engine rebuild/upgrade. Depending on how far you wanted to go I figure the job will cost between $5,000 to $10,000 just for the engine. At least for me the question then becomes what do I gain versus the long term investment.
 
I do like the idea of a stronger engine for the car. If I had the extra money.
 
Art

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 Posted: 01-05-2013 05:46 pm
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Jensen Healey
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The upgrade to the lip seal occurred in 1973 while the older square corner headlight surrounds and two piece wings were still in production.

One problem with upgrading the 907 crank is flexing in the main bearing area. There were countless upgrades throughout the 25 year life of the 900 series engines but Lotus never stroked the crank past 2.2 liters. I wonder why?

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 Posted: 01-07-2013 03:25 pm
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roverman
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Raw forging, I am considering is 4340 chrome moly steel. This is likely 3x the strength of the cast iron crank. When the crank is stronger, it will flex the main webb area-less, for a given load. Anyone have the deck height, for these engines ? I havent dissasembled one yet. Thanks, roverman.

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 Posted: 01-10-2013 06:15 pm
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gmgiltd
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Lotusbit's in the UK do a 2.6 litre kit - not sure how much is bore or stroke. They use the engine for racing and have it in a Nissan Micra

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 Posted: 01-11-2013 03:56 pm
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roverman
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I find no link/info, on their webbsite, for such a build. Regards, roverman.

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 Posted: 01-12-2013 04:37 pm
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Jensen Healey
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http://lotusbits.com/upgrades_engine.html

Use the scroll bar on the right and scroll to the bottom. There you will also find a link to a pdf.

Kurt

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 Posted: 01-31-2013 10:33 pm
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roverman
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They list a 2.5L for only 10k Sterling. First I find a crank. Cheers, roverman.

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