[Hi Jon, you have to measure the combustion chamber size. Every RB cylinder head is different and every individual cylinder is different.
In my opinion 280 degree cams (particularly inlet) are too long in the duration for an RB30. Based on what I have seen on several engines, 280's don't work efficiently until 5,500 rpm, which is too high for an RB30. Unless you are aiming for 800+ bhp of course. The max duration I would use is 272 for the inlet, even 264's work great for a raod engine You might just get away with 280 on the exhaust, it depends on what you are going to use the engine for. ]
Thanks SK
Sorry for some reason i got 280 in my head checking my msn history its 272, what i want to do is, i got a gt35/40 with a .82 houseing i was planning on the turbo to be spooled up buy 3500-4000, then the cams kick in about 4500, so basicly offsetting the "lightswitch" type power of the turbo by making the cams come in a bit later, giving it some time to grip.. power wise hoping for 650hp ish so using the gt35 to the max (well for dyno runs)
1) will i have to upgrade the lifters to work with the 10.5 cam
2) And How do i identify what type of retainers i have so i can order the right JUN cam kit?
3) What pistons give a 9 ish cr? with the 26 head or do theyb have the be custom made?
Cheers
Jon