|Moderated by: Greg Fletcher|
|My friend Dan Walters who is helping me with the rebuild of JH Mk 1 - 13046 is asking for some info from those that have performed a successful rebuild to a 2.2 L 10.5:1 engine with a stroker crank. Would appreciate comments that will help. We are at the stage where we are trying to set up cam timing for the best performance for a street worthy car. It will not be raced. See the rebuild story for New Restoration Project 13046
Dan writes the following:
Has anyone played with the cam timing of a modified 907?
-flat top pistons 10.5:1
-107, 104 cams
-adjustable cam gears
-Dellortos (45 mm)
-4 tube exhaust header
Chuck Lakowski suggests 104 deg cam lobe center lines, both cams. Has anyone tried other numbers?
(optional, I don't want to start a war about the computer dyno...)
The Desktop Dyno 2000 seems to like 108 deg center lines, both cams, for max TQ and max HP, so far.
I'm wondering if anyone has tried this combo? Also any suggestions on settings overall for performance vs street drivability?
Last edited on 04-30-2015 04:57 pm by Randallclary@icloud.com
|Hi Randall and anyone else who may be interested in this post.
I am not familiar with Desktop Dyna 2000 but read your post with interest as I am in a similar situation.
After too many years to mention I am at the final stages of rebuilding my 2.2 motor.
My main objective was always to build a nice fun motor with the emphasis on reliability.
I have had the bottom end doweled on all 10 main bolts, the tunnel line bored and everything balanced and blue printed, from a number of sources from 5+ years ago I chose 9.5 :1 compression CP piston from JHPS. The cylinder head and 45mm Carbs came from a later Lotus with bigger ports than the original JH and I have ported it (not a Zeus head).
The Cams that came with the head are the 'E' Spec cams and I intend to time them to 102.5 deg with the HTD vernier pulleys. I also have crank fired ignition.
It will be basically a circa 1980 Spec 5 Lotus motor.
At this stage I am about to fit the head but wondering if I should change the valve springs now incase at a later date I decide to go to 104 cams or a 107 / 104 combo and the standard valve springs would not be able to handle the 104 cam lift due to coil binding.
Lotusbits in the UK advised me not to use the 'E' Spec cams as they said were never used in a 2.2, but I have read that the first series of 2.2 Lotus Sunbeams used that cam and Garry Kemp told me the E cam is a very pleasant road profile.
Since I have choosen a relatively low compression ratio I do not know if I would get the full advantage of the 104 cams?
One thing that I would be very keen to source is a suitable set of beehive valve springs, as there is a lot of literature on the net of the advantages of using a single beehive spring instead of double valve springs.
Any advise on cams, cam timing or valve springs would be appreciated.
|Hi Randall, I don't see any harm in reducing the overlap by using 108 degrees setting. You may never notice the difference on a street driven car. Have fun with it!