Land Rover Cam Details
Discussion
chassis 33 said:Pro tuning the v8? That's the one I have and it has loads of identifying stuff in for the blocks so I assumed it had it for the cams too but no. Good book which has given me confidence in my engine although I'm not entirely sure what I'll do with the knowledge from here on in
BTW Dern, is that the Des Hammill book? I've just bought that and the Hardcastle book, Des's book at first glance looks very good.
Regards,
Mark
v8 racing said:
That seems like a hell of a lot of duration for a standard cam?
It surprised me too, but it is from the LR service manual. Whether it is 285degs in absolute terms or 285degs in between the 'X' thou of lift (as most cam makers quote) I don't know (I'm guessing the former).
Later models do show reduction in duration (most likely for emissions), but it is well known that Rover V8 valvetrain is so floppy it has involuntary variable valve timing.
Be careful when comparing lift values, most performance cams measure at around 50 thou
clearance in order to get a clean lift. I suspect these figures are at zero clearance.
My TR7 runs an LR Defender 3.5 with 1mm skimmed heads to get 9:1 CR, Weber 4 barrel
with a RoverCraft RC87 cam this is from memory 26 66 cam specifically designed for
4 x 4s with manual gearboxes. In the 7 it has very little on cam effect & pulls from just over tick over. Mine needs setting up on a RR but still very impressed. Progress Engineering who used to be Rovercraft have been building RV8s for around 35 years so just might know what they're doing
It was also much cheaper than Kent or Piper ones despite coming in a Piper package! 3 years ago it was £ 110 + VAT. Just had a quick google they're now called Evenden Engineering Ltd MAIDSTONE 01622 842555
>> Edited by tr7v8 on Thursday 3rd November 18:47
clearance in order to get a clean lift. I suspect these figures are at zero clearance.
My TR7 runs an LR Defender 3.5 with 1mm skimmed heads to get 9:1 CR, Weber 4 barrel
with a RoverCraft RC87 cam this is from memory 26 66 cam specifically designed for
4 x 4s with manual gearboxes. In the 7 it has very little on cam effect & pulls from just over tick over. Mine needs setting up on a RR but still very impressed. Progress Engineering who used to be Rovercraft have been building RV8s for around 35 years so just might know what they're doing
It was also much cheaper than Kent or Piper ones despite coming in a Piper package! 3 years ago it was £ 110 + VAT. Just had a quick google they're now called Evenden Engineering Ltd MAIDSTONE 01622 842555 >> Edited by tr7v8 on Thursday 3rd November 18:47
v8 racing said:
They have to be off the seat duration figures, 285 degree duration would not make for a nice idle!! also the timing figures dont add up right, if you work the sums out on the timing figures the duration is correct but the full lift figure is wrong!!? got me stumped!!
It is either an Assymetric cam, or 13deg (+/-6.5deg at midpoint) rotation at max valve lift (from a 13deg circular chord at the top of the cam), or a screw up by LR?
I'm guessing the second option because if you do the arithmetic:
285/2=142.5 midpoint of duration
142.5-32=110.5 ATDC midpoint of IVO
110.5-6.5=104 ATDC start of max lift on inlet
Now for the exhaust:
142.5-35=107.5 BTDC midpoint of EVO
107.5+6.5=114 BTDC start of max lift on exhaust
Cheers
Phil
>> Edited by wheeljack888 on Friday 4th November 00:28
v8 racing said:
They have to be off the seat duration figures, 285 degree duration would not make for a nice idle!! also the timing figures dont add up right, if you work the sums out on the timing figures the duration is correct but the full lift figure is wrong!!? got me stumped!!
It's most likely an "assymetric profile" where by the Profile mid point is not coincident with the max lift point.
This is common on valve train designs with some kind of "rocker arm-esque" multiplier- in this case the pushrod is multiplying the cam lift. You can also see this phenomenon on engine with rocker arms with curved pads. The cam profile cam be designed to compensate for this effect before hand.
285 degree duration IS long if measured at top of ramps or at say, 0.050 inch valve lift (which I doubt) however not that long a duration if including cam ramps (which on a pushrod engine are usually massive).
285 deg duration doesn't effect idle DIRECTLY but the overlap/(how much the inlet and exhaust valves are lifted off the seat at TDC) DOES effect idle. For instance you could have a big duration cam phased such that the IVC is very late and there is little overlap.
In the rough guidelines I have, for 2 valve engine with hydraulic lifters you don't want to lift the valve more than 1.9 mm at TDC if you want to retain a stable idle.
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff