View single post by Judson Manning
 Posted: 05-06-2008 01:32 pm
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Judson Manning

Joined: 03-14-2005
Location: Atlanta, Georgia USA
Posts: 406

The 104IN/107EX represents the results of ~15 years of evolution for the 907/911/912 engine family.  Keep in mind the 907 was really a prototype with little product development when delivered to Jensen in 1972.  As time went by and Lotus received a lot of customer/racing feedback they made applicable changes to the engine (not just the camshaft).

'The Shark' built by the Master Gary Kemp takes that evolution a bit further as Erik was interested in something quite wild.  Gary began with the Excel SE (912 104/107 + 35mm chokes) platform and added things like the latest Lotus Zeus head casting found in the post 1995 Esprit.  Erik CAN use 38mm chokes precisely because the head + cam + 2.2 crank CAN flow that ridiculous amount of fuel+air.

Kurt does make mention of alternate springs to which I will add the need to do substantial head porting to take advantage of the additional lift of the 104.  Take a look in the gallery to see the differences in intake port sizes from early to late JH engines.  The later Esprit heads make the JH head look tiny.

Also take into account the 107 evolution put it running a 104^ lobe center vs. the stock 110^ lobe center.  Slapping a set of 107s on stock JH cam sprockets will chop-off breathing over 5000rpm, but it will be a low-end torque moster for around town.  Spring for a set of HTD sprockets with the 104^ 'green dot' if you want higher end breathing.

If all you want to do at this stage of the game is put in a new set of cams, I'd buy and install the 107s on your stock cam wheels and feel the difference.  If you are not happy with the results dish out another ~$300 for green dot sprockets.  Assuming that is still not enough, spend $1,500.00 on a full porting job and install the 104 (with green dot sprockets).

IMHO installing a 104/107 combination on stock JH sprockets (110^ LC) and a stock JH head might not be the best solution.