Poncams Or Larger For Rb25/30

[AD4M]

back to the topic on disabling the vct to run an adjustable gear, what cam can then be fitted? are you still limited to the 8.5 tomei poncam or can something else be used??

this is for the non neo head btw

[Dale FZ1]

The limitation on cam lift comes from valve spring dimensions, and how much they can be compressed before encountering spring bind. You'll strike some variance, but without machining the head to counter that problem my RB25 head was best spec'd with max lift under 9.0mm. It is something best tested on the bench with measuring equipment, and in consultation with a spring supplier who will work with you or your machinist.

My view is that the 25 head is a sound "street" spec head, while the 26 is made for "race". Uprate your cam spec for sure, but keep it under 9.0mm / 265 degrees and it will serve well. If you want more than that probably best to go straight into a 26 head and use the bigger/better hardware available for it. I don't see sense in spending money on a 25 head to try to emulate the results of a 26.

[AD4M]

The limitation on cam lift comes from valve spring dimensions, and how much they can be compressed before encountering spring bind. You'll strike some variance, but without machining the head to counter that problem my RB25 head was best spec'd with max lift under 9.0mm. It is something best tested on the bench with measuring equipment, and in consultation with a spring supplier who will work with you or your machinist.

My view is that the 25 head is a sound "street" spec head, while the 26 is made for "race". Uprate your cam spec for sure, but keep it under 9.0mm / 265 degrees and it will serve well. If you want more than that probably best to go straight into a 26 head and use the bigger/better hardware available for it. I don't see sense in spending money on a 25 head to try to emulate the results of a 26.

cheers for that mate!

we're looking at the camtech 264 9.0mm cams atm and definatly going to be installing stiffer springs while its apart getting serviced. not looking for massive top end power but more driveable/streetable power delivery.