Discussion
9XX compression is raised by installing new pistons. There are a number of piston brand names available for the 907, but JE Pistons have the Lotus range covered very well.
The cylinder head can be shaved if necessary to flatten the surface of a slightly warped head, and that would also slightly increase the compression ratio; but the cut depth that is allowed would NOT result in a large enough increase in CR to justify the effort. Besides, cutting the head results in the cams being retarded as the tensioner pulls the new-found slack in the belt up & over the cam pulleys.
You are correct that the full potential of the 104 cams won't be realized unless you also increase the compression ratio. Always keep the three C's in balance (Cams, Carbs & Compression).
Regards,
Tim Engel
The cylinder head can be shaved if necessary to flatten the surface of a slightly warped head, and that would also slightly increase the compression ratio; but the cut depth that is allowed would NOT result in a large enough increase in CR to justify the effort. Besides, cutting the head results in the cams being retarded as the tensioner pulls the new-found slack in the belt up & over the cam pulleys.
You are correct that the full potential of the 104 cams won't be realized unless you also increase the compression ratio. Always keep the three C's in balance (Cams, Carbs & Compression).
Regards,
Tim Engel
Hi
Note you have the 907 in a 7. I have a 910 in a Sylva, never come across any one else who had put one in a 7 type chassis before, don't know why as they are light.
to answer your question the advice fro Tim Engle is of course right, you can skim the head a little, although the manual says not to, and then go for HC pistons, But look at a crank as well, 2 liter pistons and 2.2 are not interchangeable, but if you get a 2.2 crank you can put it in a 2 liter 907 with existing rods head etc, and 2.2 HC pistons.
Best price is the Jensen Healy preservation society in LA, they sell a strocker kit with crank and pistons, Pistons are either JE or CE and plus 30 so you need a rebore. My advice if you go this way is make sure your rods are in spec, as if the engine has ever over rev'd these pistons will touch the head. I have CE 11:1 pitons and have had a small step machined off the crown of the piston, around the circumference to stop it hitting the head. JHPS is the best source of advice and parts I have found for the 900, their engine page/chat is very good.
Running this with high lift 290 duration cams, S300 valves, etc. Lotus has done a simulation for me and have calculated power at over 250 BHP, I think this is optimistic but it was run for me at Hethall on the right software, so it should be right.
Any way tell me about the 7, mine is a Phoenix, chassis was made with a wider tunnel to take a Gareg gear box, and back axel is Lotus Sunbeam LSD. All up weight is 628 KG, I run the car in the Classic Care series at Sepang F1 track, and I have been trying to find any case of a 900 engine running/racing in a seven type chassie, to support my race eligibility. So any info you would disclose is of interest.
Regards Kelvin
Note you have the 907 in a 7. I have a 910 in a Sylva, never come across any one else who had put one in a 7 type chassis before, don't know why as they are light.
to answer your question the advice fro Tim Engle is of course right, you can skim the head a little, although the manual says not to, and then go for HC pistons, But look at a crank as well, 2 liter pistons and 2.2 are not interchangeable, but if you get a 2.2 crank you can put it in a 2 liter 907 with existing rods head etc, and 2.2 HC pistons.
Best price is the Jensen Healy preservation society in LA, they sell a strocker kit with crank and pistons, Pistons are either JE or CE and plus 30 so you need a rebore. My advice if you go this way is make sure your rods are in spec, as if the engine has ever over rev'd these pistons will touch the head. I have CE 11:1 pitons and have had a small step machined off the crown of the piston, around the circumference to stop it hitting the head. JHPS is the best source of advice and parts I have found for the 900, their engine page/chat is very good.
Running this with high lift 290 duration cams, S300 valves, etc. Lotus has done a simulation for me and have calculated power at over 250 BHP, I think this is optimistic but it was run for me at Hethall on the right software, so it should be right.
Any way tell me about the 7, mine is a Phoenix, chassis was made with a wider tunnel to take a Gareg gear box, and back axel is Lotus Sunbeam LSD. All up weight is 628 KG, I run the car in the Classic Care series at Sepang F1 track, and I have been trying to find any case of a 900 engine running/racing in a seven type chassie, to support my race eligibility. So any info you would disclose is of interest.
Regards Kelvin
Berw said:
Hi
Note you have the 907 in a 7. I have a 910 in a Sylva, never come across any one else who had put one in a 7 type chassis before, don't know why as they are light.
Kelvin,Note you have the 907 in a 7. I have a 910 in a Sylva, never come across any one else who had put one in a 7 type chassis before, don't know why as they are light.
Way back when, there was a company in New Zealand that produced a Seven under license to Lotus. Sort of a Caterham deal for that part of the world. Anyway... their standard model used a 907 engine. I saw one once in Hong Kong.
Regards,
Tim Engel
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