Lets talk: Cam Shafts
#18
#19
Yes I meant the standard cam. I have an uprated one on my car, but just wondered as I always thought that the 2.5 cam would obviously not have been optimised for a 3.0. But in the real world is there much difference? I know some do still use the factory cam in their 3.0 conversions. I have not had the chance to see the improvements my uprated cam has made yet.
#20
The only way to tell would be to put the car on a dyno with each cam.
Aside from that, usually a guy with some experience can put two cams side by side and tell you what the GENERAL differences of the cams are
Aside from that, usually a guy with some experience can put two cams side by side and tell you what the GENERAL differences of the cams are
#21
What do you mean by "wider"? Like more duration?
I can't see that displacement would affect cam choice, really.
One could argue that bigger cylinders don't like to rev as high, therefore requiring a milder cam; especially if it's a 16 valver, which by nature can already flow a little more air at higher RPM.
You would think.
#22
I have used both the 5R (turbo) camshaft and the 9R (Late NA) camshaft on the 3.0 and I haven't noticed much of a difference on the butt dyno.
The 9R should allow for slightly better engine breathing in higher revs and I feel it did so above 4000rpm, though maybe to a rather limited extent, and it still may be a placebo effect.
I am using the 5R camshaft again now as :
- I see little point revving such big 4 pots much beyond 6000rpm
- though I'm running a 3" straight-through exhaust now I think that my KKK turbine will still make more backpressure than a modern turbine. I don't have figures to back this up, but I prefer erring on the safe side and optimising reliability at the price of ultimate top end power as the engine has a pleasant display of power already with the 5R camshaft.
Nick, you mentioned in the past you were not satisfied with how your turbo spooled, don't you think that could be due to your "uprated" camshaft?
The 9R should allow for slightly better engine breathing in higher revs and I feel it did so above 4000rpm, though maybe to a rather limited extent, and it still may be a placebo effect.
I am using the 5R camshaft again now as :
- I see little point revving such big 4 pots much beyond 6000rpm
- though I'm running a 3" straight-through exhaust now I think that my KKK turbine will still make more backpressure than a modern turbine. I don't have figures to back this up, but I prefer erring on the safe side and optimising reliability at the price of ultimate top end power as the engine has a pleasant display of power already with the 5R camshaft.
Nick, you mentioned in the past you were not satisfied with how your turbo spooled, don't you think that could be due to your "uprated" camshaft?
Last edited by Thom; 12-02-2011 at 06:47 AM.
#23
Just to throw something else into the mix. With some of these 3L builds even though we're discussing longer throw and larger pistons, many people use lighter pistons and rods, lighter flywheels, and lightened cranks which I assume would help offset the former. I use a larger cam on my 2.5L and do find that I feel the need to rev to higher rpms but the car was a bit lighter than stock so this was not so bad. On Sean's '86 with turbo S2, his car is probably a bit heavier than stock weight due to bigger brakes, tyres, exhaust, motor. It feels pretty linear but it doesn't drop away like stockish 8v's. I don't believe it suffers too much loss of tq down low either, at least not when I was passenger on the track. I'd still consider a bigger cam on a 3L 8v build assuming a few other parts were modified. Having said that, even if you only increase the capacity and do nothing else, the 3L motors are very intoxicating.
#24
What do you mean by "wider"? Like more duration?
I can't see that displacement would affect cam choice, really.
One could argue that bigger cylinders don't like to rev as high, therefore requiring a milder cam; especially if it's a 16 valver, which by nature can already flow a little more air at higher RPM.
You would think.
I can't see that displacement would affect cam choice, really.
One could argue that bigger cylinders don't like to rev as high, therefore requiring a milder cam; especially if it's a 16 valver, which by nature can already flow a little more air at higher RPM.
You would think.
Maybe some people running 3 liter engines can benefit from this.