nick_968

How good is the standard cam on a 3.0 setup?

gruhsy

By standard you are meaning the same cam as a stock 2.5L??????

lee101315

Good question...I imagine the cam lobes should be made a bit wider for an engine with a longer stroke. I guess you would benefit from having the cam reground to get some more torque out of that engine.

nick_968

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.

lee101315

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

TurboTommy

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.

Thom

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?

333pg333

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.

lee101315

Im not going to get into a discussion on duration vs lift and rpms,but I can tell you what many factory cars such as bmw and porsche do when they substantially increase displacement on an engine. They increase the base circle of the lobe without changing the lift much, which is done precisely for a larger displacement. It doesnt move the power band at all to the right.

Maybe some people running 3 liter engines can benefit from this.

Paulyy

what if you keep the same duration but have more lift? on both intake and exhaust?