B
Badger
Guest
Hi all, just thought I'd post this for general perusal.
Please, Please, Please - read this carefully before buying a new camshaft -
from anyone!
It seems to me that if you are looking for a cam for a v8, there are a lot
of suppliers out there. Some of them are good companies to deal with, some
not so good. That is a matter of personal choice who anyone wishes to deal
with.
BUT - Here is the problem.
Some companies are advertising cams in the comics (and one in particular on
ebay) as being suitable for either carb or EFI engines. This is not so, the
cams are completely different and if you fit the incorrect cam to a carb
engine then the fuelling will be all over the place.
Allow me to quote some cam figures, taken from genuine parts workshop
manuals.
Vehicle/engine IO IC EO EC Duration Lift
RR 3.5EFI 24 52 62 14 256 0.39
RR 3.5 Carb high comp 36 64 74 26 280 0.39
RR 3.5 Carb low comp 30 75 68 37 285 0.39
Rover SD1 carb & EFI 30 75 68 37 285 0.39
RR 3.9 EFI 32 73 70 35 285 0.39
IO is inlet opening, degrees before top dead centre
IC is inlet closing, degrees after bottom dead centre
EO is exhaust opening, degrees before bottom dead centre
EC is exhaust closing, degrees after top dead centre
Duration is the number of degrees the valve is off it's seat for (measured
at only a couple of thou')
Lift is the lift at the camshaft lobe, not the valve.
Please note that the 3.5 EFI engine can use either the 256 or 285 duration
cams, with the same injection system, BUT the fuelling is different, check
the part numbers of the ECU's for a Rangie and an SD1 Vitesse for
confirmation.
Check also the differences between the carb and EFI cams for a rangie, how
can anyone sell a single cam and say it is suitable for bolting straight in
to either engine??
It can be seen from this that the difference between a low compression carb
cam and a 3.9 cam is only 2 degrees of overall timing, so do not be fooled
into believing that a 3.9 cam will make your 3.5 fly, most noticeable
difference is down to replacing a normally shot cam with a new one, you'd
have noticed the same if you'd have put a new std cam in!
Advancing a cam in this way will slightly enhance the low rpm torque, but it
will be measurable only on a dyno, not by you or I driving it! As for power,
if anything it will reduce very, very slightly. You will lower the peak
torque and peak power rpm's by around 200rpm, that is all.
Be careful what you buy and don't get ripped off by advertising blurb folks!
Just in case anyone thinks I'm trying to promote my own sales, I don't stock
or sell engine parts, I buy in for myself as and when I need them to carry
out my rebuilding work.
Badger.
Please, Please, Please - read this carefully before buying a new camshaft -
from anyone!
It seems to me that if you are looking for a cam for a v8, there are a lot
of suppliers out there. Some of them are good companies to deal with, some
not so good. That is a matter of personal choice who anyone wishes to deal
with.
BUT - Here is the problem.
Some companies are advertising cams in the comics (and one in particular on
ebay) as being suitable for either carb or EFI engines. This is not so, the
cams are completely different and if you fit the incorrect cam to a carb
engine then the fuelling will be all over the place.
Allow me to quote some cam figures, taken from genuine parts workshop
manuals.
Vehicle/engine IO IC EO EC Duration Lift
RR 3.5EFI 24 52 62 14 256 0.39
RR 3.5 Carb high comp 36 64 74 26 280 0.39
RR 3.5 Carb low comp 30 75 68 37 285 0.39
Rover SD1 carb & EFI 30 75 68 37 285 0.39
RR 3.9 EFI 32 73 70 35 285 0.39
IO is inlet opening, degrees before top dead centre
IC is inlet closing, degrees after bottom dead centre
EO is exhaust opening, degrees before bottom dead centre
EC is exhaust closing, degrees after top dead centre
Duration is the number of degrees the valve is off it's seat for (measured
at only a couple of thou')
Lift is the lift at the camshaft lobe, not the valve.
Please note that the 3.5 EFI engine can use either the 256 or 285 duration
cams, with the same injection system, BUT the fuelling is different, check
the part numbers of the ECU's for a Rangie and an SD1 Vitesse for
confirmation.
Check also the differences between the carb and EFI cams for a rangie, how
can anyone sell a single cam and say it is suitable for bolting straight in
to either engine??
It can be seen from this that the difference between a low compression carb
cam and a 3.9 cam is only 2 degrees of overall timing, so do not be fooled
into believing that a 3.9 cam will make your 3.5 fly, most noticeable
difference is down to replacing a normally shot cam with a new one, you'd
have noticed the same if you'd have put a new std cam in!
Advancing a cam in this way will slightly enhance the low rpm torque, but it
will be measurable only on a dyno, not by you or I driving it! As for power,
if anything it will reduce very, very slightly. You will lower the peak
torque and peak power rpm's by around 200rpm, that is all.
Be careful what you buy and don't get ripped off by advertising blurb folks!
Just in case anyone thinks I'm trying to promote my own sales, I don't stock
or sell engine parts, I buy in for myself as and when I need them to carry
out my rebuilding work.
Badger.