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Jan 26, 2008 11:32 pm
Jan 26, 2008 11:32 pm
Subject: Re: 2L engine problem
I would be very surprised if, on it's own, the change of cam profile solved this problem. The square top cams go back to pre-war days and were standard for 2 litres for many years. I must have run them in my car for at least 30 years without a spit back problem. About 8 years ago I redesigned the cam profile from basic principles and came up with a more rounded top profile and a slightly concave flank. This was adopted by LMB (with my agreement) and subsequently the club produced new shafts with a similar shape. I run with 45 degrees of overlap. (IVO 20 BTDC EVC 25 ATDC) and the car is totally tractable, ticks over sweetly at 600 rpm. It is true that this amount of overlap does not enhance the performance below 2500 rpm, but after that she pulls strongly all the way up to 4500. I do think you need to rev the 2 litre engine to get the best out of it, strange for such a long stroke engine.
I would be very surprised if, on it's own, the change of cam profile solved this problem. The square top cams go back to pre-war days and were standard for 2 litres for many years. I must have run them in my car for at least 30 years without a spit back problem. About 8 years ago I redesigned the cam profile from basic principles and came up with a more rounded top profile and a slightly concave flank. This was adopted by LMB (with my agreement) and subsequently the club produced new shafts with a similar shape. I run with 45 degrees of overlap. (IVO 20 BTDC EVC 25 ATDC) and the car is totally tractable, ticks over sweetly at 600 rpm. It is true that this amount of overlap does not enhance the performance below 2500 rpm, but after that she pulls strongly all the way up to 4500. I do think you need to rev the 2 litre engine to get the best out of it, strange for such a long stroke engine.