Cam timing durations:

Because it is possible to noticibly change the power curve of an engine through intake and exhaust tuning the effect of the camshafts on top of existing modifications can only be approximately guessed. All the figured below should only be used as a rough guide. Note as there is some much speculation as to what cam profiles work with VVT still that there are no solid answers, so for the purposes of this guide it is assumed the maximum with a high lift is 270 degrees.

Note- Quoted durations: All the durations quoted in this article are quoted in degrees measure from the point of zero lift. Some camshaft companies (particularly American) quote their durations from a set lift, eg: 220 degrees at 0.1”. Quoting the duration from a positive lift is a more accurate method however there is no set standard of what lift duration should start to be measured. To complicate things further durations measured from different lifts can't be compared to each other or even readily worked out one figure from another. As a general rule all Japanese grinds are measured from a zero lift point.


250 degrees duration (original): Both 20v engines are 250 degrees in duration which is considered to be somewhat aggressive for a cam fitted to an unmodified engine. With the right tune, still functional VVT, intake and exhaust mods these can still make good power with a solid torque curve. With an adjustable cam gear on the exhaust cam the cam timing can be varied. One report from a tuner suggested a power gain in the top end by retarding this exhaust gear 2 degrees. Please read 'adjusting cam gears for more information'.

250+ to 270 degrees duration: The cost of changing the camshafts in a 20v engine is no small thing considering the cost of the cams by them self and then the process of re-shimming the valve clearances to suit.  Because of this I personally believe it nullifies the 250 to 270 degree camshaft choice because using decent 270 or 272 degree camshafts will result in no power loss anywhere in the rev range, so by using something such as a 260 degree set it would be a very high cost vs gain ratio.

270 degrees duration: This would be a cam upgrade to either 270 or 272 on the intake with the VVT still intact and 270 to 280 on the exhaust. Running VVT with a pair of 270 degree cams with the right grind will lead to no power loss at all anywhere in the rev range, instead it will help with the mid range and also at the upper end of the rev range. Changing to a 280 degree grind on the exhaust side should in theory lift the power curve higher in the rev range, this 270/280 degree set should in theory be an excellent choice for most 20V owners.

272+ to 280 degrees duration (intake):While open to much debate; there may be a point where VVT is no longer an option. The speculation is that the cam pulley might move too much in angle. Some have questioned valves hitting pistons however because the VVT pulley is meant to work by retarding the intake it should by rights make the valves open later and hence no closer to the pistons. This is a topic of much hearsay and speculation, this author has no personal experience in this area.



Adjusting cam timing:

A normal adjustable cam gear off a 16V will fit right onto both the silver and blacktop exhaust cams just like the original. However whenever this exhaust gear is adjusted the crank angle sensor will have to be moved to re-adjust the timing as it is also altered with the cam gear adjustment. For the intake it is not possible to readily adjust the cam timing with the VVT still intact. The VVT pulley can be replaced with an adjustable cam timing gear such as the model from Toda called the “VVT canceling gear”. However some aftermarket camshaft grinds are shaped in the same way as a 16V camshaft on the front so they are able to use a normal 16V adjustable gear for the intake also. Another option is a modification of the original VVT solenoid to become adjustable. Because there is some movement in the gear a mechanical mechanism could be welded to the front face to hold it in a fixed position.

When adjusting the exhaust cam timing care must be taken because when adjusting the gear the crank angle sensor will also have its position offset. So if the exhaust cam is for example retarded 2 degrees then the crank angle sensor would have to adjusted accordingly.




Brand name or local grind:

Multiple Companies offer off the shelf camshafts for a 20V engine. Some of the imported cams from Japan have quite a high price compared to what local camshaft grinding shops may offer them for. With the exception of cams designed to be shorter on the intake to suit a 16V the rest are very likely ground from the same blanks using the same specifications. This is because Toyota still sell 20V blank cams for cam grinders to choose whatever is wanted.




Silver Vs blacktop cams:

The blacktop engine has a slightly different cam profile than the silvertop. The only real difference between them is 0.23mm more lift on the intake and 5 degrees more offset. So while they can be readily swapped (may require VVT pulley to be swapped also) it will provide a negligible power upgrade and hence be a fairly futile exercise.