Tomei Procam head machining

[DiscardTheWeak]

Hello all, I am researching a cam setup for my RB26. Can anyone please confirm from their experience, whether or not Tomei Procam 260 10.25mm lift cams need head relieving for lobe interference? The common answer is yes, anything over 9.8 or so, you need machining. It my understanding that this is only true with factory base circles, which is why many companies make base circles smaller, such as the Tomei Procam which use 30mm base circles, OEM being 32mm. HKS use 31mm in the step 2, I believe JUN does as well. When installed with Tomei lifters, do the 10.25mm Procam become drop in? Thank you

 

 

[GTSBoy]

Anything with a 2mm decrease in base circle diameter is going to clear up to ~10.8mm, obviously enough.  Why would it not?  Arithmetic is all you need to sort that out.

[DiscardTheWeak]

7 hours ago, GTSBoy said:

Anything with a 2mm decrease in base circle diameter is going to clear up to ~10.8mm, obviously enough.  Why would it not?  Arithmetic is all you need to sort that out.

Thank you. Thats what I was thinking, however that is not exactly what the common response its on the forums. Basically,  you gain half of the base circle reduction in clearance. So a 31mm base circle, like HKS step 2 will gain .5mm more clearance? Is the common consensus that 9.8mm is the highest acceptable lift on a stock base circle without modifying for clearance? Technically making an HKS 31mm base circle, 10.2 mm lift, drop in as well? Thanks for the info, these companies are hard to get in touch with 

[mrpav]

I’d love confirmation on this also, I’ve searched and searched with mixed info. 
 

Ive ordered a set of 10.7mm lift cams but the base circle is 30mm so I’m hoping the lobes don’t foul on the casting due to the reduced base circle.