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| Joined: | 03-14-2005 |
| Location: | Atlanta, Georgia USA |
| Posts: | 406 |
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Greg is correct in that a cost effective rebuild would re-use the 8.4 pistons assuming the liners are in good shape. The 'development' engine in my E-Prod car is a freshened 8.4 with touched-up liners and new rings. ~$1000 in savings. Alternatively, if the liners need more than ~.003" machining then new pistons are in order. With modern gas able to handle well over 10:1 c/r, it's kind of a waste to purchase new 8.4 pistons given the performance increase.
From a cam perspective Lotus progressively dropped the duration and overlap with the introduction of the E and 107 cams to boost torque. The dyno results I have from John Cronin's 2.0 with dual 107 cams and 104LC show a wide and flat torque curve with HP peaking at 5,750rpm - perfect for a street car.
In the quest to run up to 8000rpm the problem is the mains holding enough pressure to feed the rod bearings. The stock main bearings have a wide and shallow groove with a big hole in the middle - just like a rain tire! To spin that high it's necessary to upgrade to the plain bottom bearings (Esprit or Chrysler) with a cross-drilled crank so that oil film can work undisturbed.
Judson