My understanding is that the early TR250/TR6 cam lift was .214. 1.75
Roller Rockers will give you .374 valve lift. I think .425 valve lift is
max for standard TR6 dual coil valve springs.
The later TR6 cam is .244 cam lift which gives .427 valve lift with 1.75 RR.
Might be wise to check other sources to be sure.
My info cam from http://www.integralcams.com/tr-250_tr-6.htm
Don Malling
Simms, Bruce CIC wrote:
> The head is off my 73 and at the machine shop for repair and upgrade.
Will
> get hot tanked, crack tested, shaved to 9.0 compression, port
matching and
> relief of valve shrouding as recommended by various listers. Mechanic
> reported several bad exhaust valves and valve seats. Bottom end
looks good
> as examined with head off. 69-73 (CF12500) camshaft is not ideal for
> performance, so something needs to be done. Dyno test curves in Comp Prep
> Manual indicate that camshaft upgrade is crucial. With head off, it's
> probably what, an additional 3 hours for my mechanic to change the cam.
> Would send my old cam and lifters to be re-ground at a cam specialist
such
> as Colt Cams in British Columbia. (I'm in Canada). Also have HS6s,
header
> and custom dual exhaust.
>
> The other option may be roller rockers. Would roller rockers such
as Jim
> Swarthout's 1.75 ratio give me an upgrade in performance similar to a
street
> profile cam of say 270 degrees duration? Would likely do the roller
rocker
> conversion myself. Mechanic says my rockers appear to be in good
> condition. The roller rocker benefits of added efficiency and decreased
> wear are likely nice things by themselves.
>
> All advice and opinions much appreciated. The list is a tremendous
> resource. NFI in any auto related business, just trying to get a nicely
> upgraded road engine at reasonable cost.
>
> Regards, Bruce Simms CF1941UO
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