Tomei 10.8mm Procams - Clearancing?

[burn4005]

Hi Guys,

going to have the head off the car soon to fit a restrictor and the like, looking at upgrading my cams for some more power. turbos are HKS2530s.

currently have tomei 9.15mm 260's, looking to upgrade to 10.8mm 260 procams. obviously with new lifters and springs to suit.

the base circle of the 9.15s is 32mm, giving total lobe radius of 41.15mm from centre of axis.

base circle of the 10.8s is 30mm, requiring new buckets and giving a cam lobe radius of 40.8mm from centre, which is actually smaller than the 9.15s.

Does this mean the head doesn't need to have machine work done so they fit?? or is the lobe thicker on the 10.8, so it still needs some material taken off the head?

also I have HKS forged pistons, do 10.8mm need piston recesses?

Thanks

Alex

Edited March 9, 2015 by burn4005

[GTSBoy]

The whole point of the reduced base circle is to allow them to be "dropped in" (hate that term - especially with these cams!) without needing to clip the lifter bores. So yes, no machine work should be needed.

[burn4005]

i stuffed the maths a bit after a few beers.... base circle number is obviously diameter.....

Poncams = 16+9.15 = 25.15

procams med = 15+10.25 = 25.25

procams hi = 15+10.8 = 25.8

I found some tomei product spec sheets. the 10,8s need piston relief and cylinder head work.

the 10.25s do not, so there is my answer. cheers

Edited March 10, 2015 by burn4005

[GTSBoy]

Ah yes, you did stuff your numbers and I did forget about the 10.25s. You chose the biggest of the Procams.......that'll do it.

[Blackkers]

Just to clear up. The 10.25s can be installed with no modification; but the 10.8s can not?

[32GTRB]

sorry to hijack, but is there a way to tell what sized camshafts are on the car with the rocker covers off? i.e. any stamping etc on standard shafts etc?

[GTR_JOEY]

I "think" the only way to tell is to look at the surface at the ends of them.. So cam gear will have to come off

[GTR_JOEY]

In saying that you can measure the lift so you would be able to get an idea