SC cams in a 73.5?

[Sigurd]

I am fixing some oil leaks on a 2.4 with CIS, a 73.5. I also have two 3 bearing SC grind cams that I have not found use for. Should I take the opportunity to swap the cams? Drawbacks?

[E Sully]

In my reading, I hve only seen the 2.7 S cams as a recommended upgrade for the 73.5 cis.
2.7S CIS
Left 911 105 143 00
Right 911 105 144 00

[Flat6pac]

The lobes on an SC cam are too large to fit into the 3 bearing cam. What ever you have for SC has got to be inquestion.
2.7 S cams work well on that engine but youre limited on compression at 8.0 CR
Bruce

[JmuRiz]

I've head or SC grind working well on the 2.7 with CIS, but I'm not sure about the 2.4. Personally they are seem similar enough to work, but I'd let an expert chime in.

[YTNUKLR]

The cam duration (degrees) for SC cams and early 911E cams is very similar actually.

I would expect these would be somewhat similar to a 911E in terms of powerband which is a great street/sport combo.

Of course, the SC lobe separation ("Lobe Center") is much "wider" at 113° vs. 102°, which basically just means it will work well with a single-throttle-body system like CIS, whereas the early 911E cam won't (well).

flat6pac (Bruce)- you're correct; a 4-bearing cam lobe is too large to fit inside a 3-bearing early housing. However, if a 3-bearing cam is ground down on the backside ("reduced base circle"), the cam can have the same lift as the SC profile.

I actually had some cams made similar to this (actually a 964C2 profile on a 3-bearing cam), although I haven't put them in anything yet. Anyone want to try them out (they could be available as I have no use for them right now)?

The downside to putting a more aggressive cam in a motor that is low-po like a 911T is the compression is really not enough. You can be happy that you can run it on the lowest octane gas I would venture to guess you would be happier with a 2.7S CIS cam in a 2.4CIS motor, which is about 20° less total duration, and maintains better compression, and is still a nice profile for a street car.

[bgyglfr]

I have a question. If one were to go high compression with custom JE pistons, maybe 86mm, could it be more feasible to run SC cams? I was actually planning a high comp CIS 2.4-2.5 with 2.7S cams but I would really like to go with SCs if they will work successfully. I'm aiming for a street/DE hot rod motor. I know most would suggest changing intake to carbs etc but I really want the stock appearance etc.

[YTNUKLR]

Yes, higher compression with the SC cam should 'fix' it. Perhaps 9.3:1 or so. More if you have twin plug.

[Sigurd]

Thank you for the inputs. I will go with the stock cams on this one.