For The 907 Engine
by Greg Fletcher
camshafts, why would you want a pair for your car? More power, it's
A Good Thing. There's nothing wrong with the vintage 140 HP stock 907
engine- it was the cat's meow in the 1970's. But if want to keep up
on the road these days with the Bimmers and Lexus' you'll need more
pep in your step and 104 performance camshafts will help get you there.
The cams, of course, use lobes that push against the valves (through
cam followers) to open them as the camshaft rotates. The spring on the
valves return them to their closed postion after the lobe has rotated.
Cam shafts can have huge effect of how the engine runs and performs.
Standard cams and performance cams vary the engine valve timing in different
ways. Typically a performance cam will have much more overlap and may
tend to run roughly dedending on engine design. Valve lift is quite
important here as we will want the valves to open wider at higher speeds
(as the engine goes faster and moves the air fuel mixture faster). A
fixed cam, like in our Jensen (opposed to an electronically controlled
variable cam in a modern car) needs to do it's job over a wide RPM range
so it's important you find some the right cam that will feel right for
the kind of driving you do. Performance cams would normally give better
power a higher RPM rates.
I was recently corresponding with Jensen Healey owner Garry Kemp in
the UK about camshafts and what would be the a good choice for 2.2 907
conversion for street use. I'm a bit cautious about too much cam, so
I can appreciate many opinions on this topic. Garry is quite knowledable
able about 907 engines in general and on rebuilding 2.2 and even 2.4
liter conversions. Heres what he had to say about it-
"Personally I think the 104 is quite a good cam: not particularly
in a 2.0L and especially a low compression engine but if they are in
a 2.2L with decent compression (10:1+) they are perfectly easy to get
along with. I have seen in the states a bit of confusion about what
a 104 exactly is: it should be 272 degrees (at 10thou lash) and 0.415"
lift. I think there may be a few reprofiles around purporting to be
a 104 but really are just something "close enough". The 107
is a good all rounder but it does tend to run out of breath around 5500rpm
: It'll pull up to 7000rpm OK but really its starting to lose its edge
after 5500 (in a 2.2 anyway). The 104 however will pull clean and strong
to 7000 rpm, it comes alive at about 3-4000 rpm but that's not to say
there's nothing below that, it'll tick over just fine at 900rpm and
is totally docile to use in traffic. It depends what you're looking
for really but I wouldn't discount the 104."
| jensen |
tech | people & places |
message board | join |
garage | links |