Discussion
Heres most of it I copied (with his blessing) , plus a few more cams I added.
CHOOSING CAM PARAMETERS. With thanks for the help from Rob Robinson www.v8racing.co.uk
LIFT
Basically as much lift as you can get, the better your engine will perform through the whole rev range regardless of cc's. the Rover head flows it most c.f.m when the valve is something like 700 thou from is seat, (17.7 mm) the reality here is no Rover cam lifts that far because it just can’t, 600 thou (15.2mm) is about its maximum. Lift is related to duration, you can’t have lots of lift with little duration as the valve will be being opened so fast that the cam follower will just dig into the side of the cam lobe and break, so with a 600 thou lift you are going to need 320 deg of duration, and what you now have is a full circuit race cam that will only make power from 5000 rpm upwards!
DURATION
Duration is the time the valve is lifted of its seat, too little you will have no power, and too much the car will drive like a pig. However duration, lca "lobe centre angle”, and overlap are all related, its not so much the duration that kills driveability its the overlap, just 10 deg can make or break the engine. The “lca” is the angle between full lift on the inlet and full lift on the exhaust lobe, by making this wider you can tame the cam for the same given duration, however what will happen is the cam with the wider “lca” will idle better, drive more smoothly, make more bhp with a wider torque curve. The cam with the smaller “lca” will only have a benefit in the mid range, around peak torque. so in my honest opinion for a road cam I like to go for around 285-290 deg of duration with a wide “lca” around 114’. This to make a good road sports cam, you can drive it down the shops with no hunting and use it on a track day as well, the same cam on a 108’ “lca” will make it more peaky in the mid range, but you will have to keep changing gears in slow traffic and it will drop off the cam quicker too, peak power will be around the same but where the 114 will still be making good power at say 6500 rpm, the 108 will be dead and buried and need a gear change. A race car is totally different I would spec a cam to work in the rev range I wanted and make the most of that rev range.
NOTE Max valve lift with standard springs is .464". Note the rocker ratio is 1.5:1 so the physical cam lift is correspond less.
Some popular cam performance and (some) specifications
Standard RV8 285" .39" 5000-5400 rpm
Hurricane 262' .433" 1000-6000rpm Better than standard RV8, but a bit "soft". Good for auto boxes
Typhoon 276 '.48" 1200-6200 rpm Needs valve springs and possibly guides-. Good all rounder
MC1 Good idle, excellent drive ability, reasonable bhp.
MC2 Mediocre idle, mediocre drive ability, good mid range, good bhp.
H404 Very poor idle, very poor drive ability, good mid range, excellent bhp
Stealth. Very good idle, excellent drive ability, moderate mid range, good bhp.
Piper 270 272' .42" 1500-6000 rpm Good idle, good mid range, poor BHP.
Piper 285 276' .440" 2000-6500 rpm. Bad idle, poor drive ability, very good mid range, good bhp but falls off the cam very quickly.
Piper 300 Bad idle, poor drive, moderate mid range, good bhp
Kent 200 Very good idle, good drive, poor every where else
Kent 218 Good idle, good drive, good mid range, poor bhp
Kent 214 Ok idle, ok drive ok mid, range ok bhp
Kent 224 Poor idle, poor drive, good mid range, good bhp
Kent 234 Bad idle, bad drive, good mid range, excellent bhp,
These are all based on the fact that you will be running standard management systems and a plenum, there are of course many more cams out there but these are the general ones you will buy.
So to sum things up a bit, if you want a good low down nice driving torque cam go for a cam with a max of around 270 deg duration and a lca of around 112 deg.
If you aren’t bothered with idle qualities and want a good mid range cam go for one with a low lca and around 280 deg of duration. If you want a track day cam or fast road cam go for around 300 deg and around 110 lca. If you want a good all rounder go for around 285 deg and wide 114 lca. Both Kent and Piper will make cams to what you want within reason so give them a call, the piper 285 for instance, loses nearly 25 bhp over the 404 at the top end, this on a controlled dyno not a rolling road, but it gains around 10 ftlb at around 200-3000 rpm, but if you asked piper to grind it on an lca of say 110’ you would only be losing around 10 bhp at peak, but gaining around 20 ftlb at 2000-3000. Please note however cams cannot be judged against other cams on rolling roads, especially different rolling roads, there are too many variants, all the way from the air filter to the oil in your gearbox and diff!
Throttle bodies against plenums and cams
What I briefly said earlier with large overlap cams, this will murder an engine running a plenum, where as on throttle bodies it tends to smooth things out a bit. Take a single plenum and all 8 cylinders draw from this one opening, which is good as each cylinder can draw as much air as it wants with no restrictions as far as air flow is concerned. The BIG DOWNSIDE TO A PLENUM, on the overlap period part of the cam, this is where both exhaust and inlet valve are open at the same time, i.e. at the end of the exhaust stroke where the piston is forcing the burnt gas out the exhaust port the inlet valve opens before the exhaust is shut, instead of the unwanted rubbish going out the exhaust it is sent back up past the inlet valve and into the plenum. This is more aggravated by the fact that the next cylinder is sucking hard and will suck the waste out of the disposing cylinder into the good one, so instead of the new cylinder getting a good charge of fresh air and fuel it has 20 or 30% of nothing that cant be ignited, hence poor combustion poor idle and low power. This is only a problem at low rpm as at high rpm you have the advantage that the exhaust manifolds "should" be scavenging the fresh inlet charge into the cylinder. If you have the money to go to throttle bodies then this is where the biggest gain is going to come in the low to mid range, on the overlap period each cylinder can only contaminate its own cylinder, and part of this will be lost to the atmosphere anyway, so generally lets say at below 3000 rpm a plenum is giving a cylinder 70% of fresh charge to be ignited a set of throttle bodies will be giving 90% at the equivalent rpm all this = more ft-lb of torque, just be careful you don’t go too small on the throttle bodies or this will hurt the top end breathing, you have gone from a 72 mm plenum and as I said each cylinder will see 72 mm down to what ever size your throttle bodies is.
Rob Robinson
CHOOSING CAM PARAMETERS. With thanks for the help from Rob Robinson www.v8racing.co.uk
LIFT
Basically as much lift as you can get, the better your engine will perform through the whole rev range regardless of cc's. the Rover head flows it most c.f.m when the valve is something like 700 thou from is seat, (17.7 mm) the reality here is no Rover cam lifts that far because it just can’t, 600 thou (15.2mm) is about its maximum. Lift is related to duration, you can’t have lots of lift with little duration as the valve will be being opened so fast that the cam follower will just dig into the side of the cam lobe and break, so with a 600 thou lift you are going to need 320 deg of duration, and what you now have is a full circuit race cam that will only make power from 5000 rpm upwards!
DURATION
Duration is the time the valve is lifted of its seat, too little you will have no power, and too much the car will drive like a pig. However duration, lca "lobe centre angle”, and overlap are all related, its not so much the duration that kills driveability its the overlap, just 10 deg can make or break the engine. The “lca” is the angle between full lift on the inlet and full lift on the exhaust lobe, by making this wider you can tame the cam for the same given duration, however what will happen is the cam with the wider “lca” will idle better, drive more smoothly, make more bhp with a wider torque curve. The cam with the smaller “lca” will only have a benefit in the mid range, around peak torque. so in my honest opinion for a road cam I like to go for around 285-290 deg of duration with a wide “lca” around 114’. This to make a good road sports cam, you can drive it down the shops with no hunting and use it on a track day as well, the same cam on a 108’ “lca” will make it more peaky in the mid range, but you will have to keep changing gears in slow traffic and it will drop off the cam quicker too, peak power will be around the same but where the 114 will still be making good power at say 6500 rpm, the 108 will be dead and buried and need a gear change. A race car is totally different I would spec a cam to work in the rev range I wanted and make the most of that rev range.
NOTE Max valve lift with standard springs is .464". Note the rocker ratio is 1.5:1 so the physical cam lift is correspond less.
Some popular cam performance and (some) specifications
Standard RV8 285" .39" 5000-5400 rpm
Hurricane 262' .433" 1000-6000rpm Better than standard RV8, but a bit "soft". Good for auto boxes
Typhoon 276 '.48" 1200-6200 rpm Needs valve springs and possibly guides-. Good all rounder
MC1 Good idle, excellent drive ability, reasonable bhp.
MC2 Mediocre idle, mediocre drive ability, good mid range, good bhp.
H404 Very poor idle, very poor drive ability, good mid range, excellent bhp
Stealth. Very good idle, excellent drive ability, moderate mid range, good bhp.
Piper 270 272' .42" 1500-6000 rpm Good idle, good mid range, poor BHP.
Piper 285 276' .440" 2000-6500 rpm. Bad idle, poor drive ability, very good mid range, good bhp but falls off the cam very quickly.
Piper 300 Bad idle, poor drive, moderate mid range, good bhp
Kent 200 Very good idle, good drive, poor every where else
Kent 218 Good idle, good drive, good mid range, poor bhp
Kent 214 Ok idle, ok drive ok mid, range ok bhp
Kent 224 Poor idle, poor drive, good mid range, good bhp
Kent 234 Bad idle, bad drive, good mid range, excellent bhp,
These are all based on the fact that you will be running standard management systems and a plenum, there are of course many more cams out there but these are the general ones you will buy.
So to sum things up a bit, if you want a good low down nice driving torque cam go for a cam with a max of around 270 deg duration and a lca of around 112 deg.
If you aren’t bothered with idle qualities and want a good mid range cam go for one with a low lca and around 280 deg of duration. If you want a track day cam or fast road cam go for around 300 deg and around 110 lca. If you want a good all rounder go for around 285 deg and wide 114 lca. Both Kent and Piper will make cams to what you want within reason so give them a call, the piper 285 for instance, loses nearly 25 bhp over the 404 at the top end, this on a controlled dyno not a rolling road, but it gains around 10 ftlb at around 200-3000 rpm, but if you asked piper to grind it on an lca of say 110’ you would only be losing around 10 bhp at peak, but gaining around 20 ftlb at 2000-3000. Please note however cams cannot be judged against other cams on rolling roads, especially different rolling roads, there are too many variants, all the way from the air filter to the oil in your gearbox and diff!
Throttle bodies against plenums and cams
What I briefly said earlier with large overlap cams, this will murder an engine running a plenum, where as on throttle bodies it tends to smooth things out a bit. Take a single plenum and all 8 cylinders draw from this one opening, which is good as each cylinder can draw as much air as it wants with no restrictions as far as air flow is concerned. The BIG DOWNSIDE TO A PLENUM, on the overlap period part of the cam, this is where both exhaust and inlet valve are open at the same time, i.e. at the end of the exhaust stroke where the piston is forcing the burnt gas out the exhaust port the inlet valve opens before the exhaust is shut, instead of the unwanted rubbish going out the exhaust it is sent back up past the inlet valve and into the plenum. This is more aggravated by the fact that the next cylinder is sucking hard and will suck the waste out of the disposing cylinder into the good one, so instead of the new cylinder getting a good charge of fresh air and fuel it has 20 or 30% of nothing that cant be ignited, hence poor combustion poor idle and low power. This is only a problem at low rpm as at high rpm you have the advantage that the exhaust manifolds "should" be scavenging the fresh inlet charge into the cylinder. If you have the money to go to throttle bodies then this is where the biggest gain is going to come in the low to mid range, on the overlap period each cylinder can only contaminate its own cylinder, and part of this will be lost to the atmosphere anyway, so generally lets say at below 3000 rpm a plenum is giving a cylinder 70% of fresh charge to be ignited a set of throttle bodies will be giving 90% at the equivalent rpm all this = more ft-lb of torque, just be careful you don’t go too small on the throttle bodies or this will hurt the top end breathing, you have gone from a 72 mm plenum and as I said each cylinder will see 72 mm down to what ever size your throttle bodies is.
Rob Robinson
v8 racing said:
Uncle Fester said:
One of the great posts.
I would love to see an updated version with the manners of cams described when fitted to an engine with a fully mapped ECU.
you will have to wait for the book!I would love to see an updated version with the manners of cams described when fitted to an engine with a fully mapped ECU.
I'm a bit surprised about the MC2 description ? Or have i just been lucky
oggs said:
Del 203 said:
I'm a bit surprised about the MC2 description ? Or have i just been lucky
Thats why I have a MC1 
MC1 Good idle, excellent drive ability, reasonable bhp.
MC2 Mediocre idle, mediocre drive ability, good mid range, good bhp.
Exactly
I just don't have the "Mediocre idle, mediocre drive ability" plenty of the other two
as you know Oggler macdeb said:
Had mc1, not impressed at all.
Have PIPER 285, impressed. [tickover and drivability just fine and no worse than standard]
Sorry, nothing much to do with op, just me thoughts.
I think the mc1 like most cams, are very sensitive to how well ported your heads and manifolds are. My old engine had an mc1 cam and it went very well and produced good numbers(over 300bhp).Have PIPER 285, impressed. [tickover and drivability just fine and no worse than standard]
Sorry, nothing much to do with op, just me thoughts.
Edited by macdeb on Tuesday 11th November 22:20
Edited by macdeb on Tuesday 11th November 22:26
v8 racing said:
Uncle Fester said:
One of the great posts.
I would love to see an updated version with the manners of cams described when fitted to an engine with a fully mapped ECU.
you will have to wait for the book!I would love to see an updated version with the manners of cams described when fitted to an engine with a fully mapped ECU.
As many know I have Uncle Festers' (RIP) old car and the H404 with fully mapped Emerald has excellent traits throughout......
Paul.
pjac67 said:
v8 racing said:
Uncle Fester said:
One of the great posts.
I would love to see an updated version with the manners of cams described when fitted to an engine with a fully mapped ECU.
you will have to wait for the book!I would love to see an updated version with the manners of cams described when fitted to an engine with a fully mapped ECU.
As many know I have Uncle Festers' (RIP) old car and the H404 with fully mapped Emerald has excellent traits throughout......
Paul.
To be honest it makes me cringe everytime those cam definitions come up, it was written in a few minutes one night after a few beers for someone.
The book is going to happen, when i cant say for sure, me being a muppet had all the rough writing and pics on my pc, the pc got fried and i lost everything so will be starting from scratch, this time though i will be printing as i go along!!
v8 racing said:
pjac67 said:
v8 racing said:
Uncle Fester said:
One of the great posts.
I would love to see an updated version with the manners of cams described when fitted to an engine with a fully mapped ECU.
you will have to wait for the book!I would love to see an updated version with the manners of cams described when fitted to an engine with a fully mapped ECU.
As many know I have Uncle Festers' (RIP) old car and the H404 with fully mapped Emerald has excellent traits throughout......
Paul.
To be honest it makes me cringe everytime those cam definitions come up, it was written in a few minutes one night after a few beers for someone.
The book is going to happen, when i cant say for sure, me being a muppet had all the rough writing and pics on my pc, the pc got fried and i lost everything so will be starting from scratch, this time though i will be printing as i go along!!
Regards, Paul.
Gassing Station | Griffith | Top of Page | What's New | My Stuff