Which Is Better? 3k, 4k, 5k Or 7k?

[B.L.Z.BUB]

Woop just got my 4-1 extractors too. I suppose gotta sort the head. Then cam. Or is there a good cam for stock? Its my daily.

[coln72]

same ahaha it just revs out

 

I backed off at an indicated 160kmh in my high comp 5k powered ke35. On a private test track of corse :D Shit when the windows got sucked off their rubbers at about 140 or so.

[altezzaclub]

There are plenty of cam grinds to pick from. I wanted one that gave torque in the low-mid range, so I listed these as options.

 

I bought the Crow grind in the end, it opened a little faster. You will want more duration and overlap if you want revs.

 

Always buy a grind lower than what you want! There is nothing worse than an over-cammed motor in daily use!

 

0.4" is the lift maximum without going to aftermarket valve springs. The 50thou duration gives a better picture of the main part of the opening, as you will have a tappet gap that will soak up some of the 'advertised duration' figures.

Edited May 22, 2010 by altezzaclub

[Felix]

There are a lot of things that determine where the power range will be with a given cam.

 

Extractors: 4-2-1's will give more low-midrange, 4-1's will give more mid-topend.

 

Port size: Smaller ports give more low-midrange. Bigger ports more mid-topend.

 

Induction: A smaller carb will have higher airspeed through the venturis at lower revs, giving better atomisation and more torque/throttle response, it will also run out of flow sooner limiting the topend. Likewise a bigger carb will be flatter in the lowend and give more up top. Keep in mind to big just kills drivability and economy in normal everyday driving.

 

Engine capacity: A larger capacity motor will come on cam sooner and run out of cam sooner. A smaller capacity motor will need more revs to come on cam, and will make peak power further up the rev range.

 

0.4" is the lift maximum without going to aftermarket valve springs.

 

I have a cam with 423 thou lift in a late 4k with no issues with coil bind running factory springs. The springs have also been shimmed to increase the seat pressure and allow more revs before valvefloat.

 

An early 3k bigport (with its overhead o-ring type valvestem sealing arrangement) may not take as much lift as a later head as there is less distance between the underside of the spring retainer and the top of the valve guide.

Edited May 23, 2010 by Felix

[philbey]

I'm running about .480 valve lift and I cracked a spring. But it took 12 months.

 

Crow 4220's fit nicely.

 

Also, I say just buy a big fat cam and learn to love it... like you would with turbo lag!

[Jono.C]

So would the cam grinds you've been suggesting for a 4k be applicable for a 3k? or would that be different again?

[coln72]

So would the cam grinds you've been suggesting for a 4k be applicable for a 3k? or would that be different again?

 

would be more top endy in a 3k than in a 4k