Cam choice is where a lot of good builds go sideways. People pick the biggest profile the budget allows, fit it to a stock valvetrain, and then wonder why the car idles like a bag of spanners and makes less power everywhere they actually drive.
Get the profile right and the engine feels like it was always meant to make that power. Get it wrong and you have paid for a rougher idle and a worse street car.
The short answer
- For a street car that still has to behave, a mild profile with matching springs is the safe default. Idle quality and part throttle manners are worth more than a peak figure you use twice a year.
- Size up when the turbo, head work and rpm ceiling have already moved. A cam should follow the rest of the build, not lead it.
- The common mistake is fitting a big cam to standard springs and retainers. That is how you find valve float, or worse.
- Buy the springs, retainers and adjustable gears with the cam. A profile that cannot be degreed or controlled is not doing its job.
How camshafts work and what the numbers mean
Two numbers do most of the talking. Duration is how long the valve is held open, measured in crank degrees, and lift is how far it opens. GSC quote their billet profiles that way in the product name, so a set listed as 268/268 has the same duration on intake and exhaust, while 280/280 is a much bigger grind aimed higher up the rev range.
More duration shifts the torque curve up. The engine breathes better at high rpm and worse at low rpm, so idle gets lumpier and part throttle driving gets softer. On a turbo engine, duration and overlap also change how quickly boost builds, which is why a profile that suits a naturally aspirated engine can hurt spool on a turbo one.
Lift is what asks questions of the rest of the valvetrain. More lift means more spring travel and less clearance between the valve and the piston, which is why serious profiles are sold alongside spring and retainer kits. The spring has to control the valve at the rpm you are chasing.
Kelford use their own profile codes rather than plain numbers. The 1-TX272-R camshaft set for EVO 1 to 3 and VR4 4G63 and the V202-C camshaft for the 2JZ-GTE VVTi are examples of that naming. The code tells the tech line exactly which grind you are running, which matters when you ring them about timing figures.
Picking the right one for your build
Street cars and daily drivers
Keep it modest. Something close to a drop in profile with a spring set that suits it will give you more area under the curve without ruining the car. Tomei take the same view with their Poncams: their Poncam range is designed to lift performance across the rev range rather than trade the bottom end for a peak, with the SR20 S13 and S14/15 versions the popular pair.
Turbo street and track builds
A moderate turbo grind with a proper spring set holds valve control at the rpm a modern turbo actually wants to run. On an RB, that usually means a race spring set like the KVS20 for RB20DET and RB25DET, or the KVS25R for an NVCS RB25DET. On a 2JZ, the KVS02 spring set covers the standard retainer, and the KVS02-BT pairs beehive springs with titanium retainers when the rpm goes up.
Big power and drag
Once you are chasing a number rather than a driving experience, duration goes up and so does everything supporting it. GSC billet profiles like the 274/274 and 280/280 sets in the GSC Mitsubishi camshaft range exist for that job, including stroker specific R2 and R3 grinds for EVO 4 to 9. Big cams want big springs, so a titanium retainer kit like the Kelford KVS63-BTK for 4G63 EVO 1 to 9 belongs in the same order.
| If you want | Go for | Why |
|---|---|---|
| A street car that still idles nicely | A mild profile plus a matching spring set | Keeps low rpm drivability and asks nothing unusual of the valvetrain |
| Reliable valve control at higher rpm | A turbo grind with a Kelford race spring set | The spring, not the cam, is what usually limits rpm |
| Maximum area at the top | A high duration billet set with titanium retainers | Big lift needs the springs and retainers built for it |
| A quick, sensible gain on a stock engine | Tomei Poncams on the SR20 | Designed to improve the whole range rather than one peak |
What to buy with it
Springs and retainers come first. Kelford list spring sets against their own profiles, including drop in options such as the KVS25NEO-DI for the RB25DET NEO that suits the OEM retainer, and full race sets like the KVS40 for the Ford Barra. If your engine is a Barra, a 4G63 or an RB, the matching set already exists in the Kelford Cams range alongside more than five hundred other line items.
Next, adjustable cam gears. Most aftermarket profiles need degreeing to a specific timing figure, and you cannot do that on a factory gear. The Kelford adjustable cam gears cover RB20, RB25 and RB26 with the KCG25, EVO 1 to 8 and VR4 with the KCG63, the EVO 9 with a single KCG63, SR20 with the KCG20 and 1JZ or 2JZ with the KCGJZ. The RB gears come in a few colours if that matters to you, which it does to more people than admit it.
Valve stem seals, guides and, on the 4G63, a balance shaft delete kit are the parts that only surface once the head is off. Nissan builders can also compare the GSC Nissan camshaft options if the Kelford grind you want is not listed for your head.
Two things to check before the cams go in: valve to piston clearance, and whether your ECU can hold the timing where the cam wants to run. Both are cheaper to sort on the bench than after the first dyno pull.
Where NZ Performance fits
Kelford grind their cams in Christchurch, which is a genuine advantage here. A local grind means shorter lead times than an overseas order, and tech support in your own time zone. We hold Kelford stock in New Zealand and dispatch from Palmerston North, so a cam and spring package is a courier run, not a six week wait.
Start at the camshaft kits and valvetrain components hub for the full range across Kelford, Supertech, Tomei, GSC and Manley, or go straight to adjustable cam gears if the cams are already sorted. If the head is coming off as part of a bigger job, our Toyota JZ and 3SGTE rebuild guide and the RB rebuild kit guide cover the bottom end side of the same build. JZ owners weighing up VVTi against non VVTi should read 1JZ VVTi vs non VVTi and cams before ordering a profile.
FAQ
Are Kelford cams made in New Zealand?
Yes. Kelford Cams design and grind their camshafts in Christchurch, and they have been supplying the local and export performance market for decades. For a NZ builder that means shorter lead times than an overseas grind and a tech line in the same time zone.
Do I need new valve springs with a new cam?
Almost always. More lift and more duration ask more of the spring, and a tired factory spring will float or lose control at the rpm you bought the cam for. Kelford list spring sets to suit their own profiles, including beehive springs with titanium retainers on some applications.
What does more duration actually do?
Duration is how long a valve stays open, measured in crank degrees. More of it moves the power band up the rev range and softens the bottom end, which is why a cam that transforms a track car can make a daily driver worse to live with.
Do I need adjustable cam gears?
You need them if the cam has to be degreed to a specific timing figure, which is the case for most aftermarket profiles. Kelford make adjustable gears for RB20, RB25, RB26, SR20, 1JZ, 2JZ and 4G63, so the cam can be set where the grind was designed to run.
Can I fit cams without opening the engine?
On most engines the cams and springs can be changed with the head on the car, though it is fiddly and you still need to check clearances. If the pistons are going to change or the engine is coming out anyway, do the valvetrain at the same time and save the labour.
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