SC cam grind on stock 2.7 questions

earlyaircooled · 02-16-2009, 08:23 AM

I'm rebuilding my stock 75, 911s 2.7 engine. It will be stock except I will back date the exhaust to the 74 and earlier style. I have reground stock 2.7S cams and 2.7 S cams that have been reground to SC specifications.

My questions are:

1. Will I get improved performance with the SC cam grind when everything else is stock?

2. What should I expect? More bottom end, mid, top? More horsepower and or torque?

3. Can I expect any driveablility issues, like rough idle etc?

Thank you

4sd911 · 02-16-2009, 08:37 AM

Just to add to this question. Whats the best cam for basic highway driving? I have three sets of cams, '74 911 (also know as 911T CIS), 911S and 911S reground to SC spec's. All cams are US for CIS engine.

earlyaircooled · 02-16-2009, 09:12 AM

I guess what I'm after is which is best for street/performance/DE, not worried about gas mileage, but I do want it to drive nice, no rough idle etc.

4sd911 · 11:59 AM

It's a good question it seems that I've been told that the "T" cams are better at bottom end, quicker acceleration, the "S" cam are better top end performance driving. But what I don't know is if that applies to CIS engines or just the MFI/carb type engines. The SC cams give more valve lift but I don't know what you would expect for performance. I can tell you that my engine was the '74 T CIS model and is now a S CIS with SC cams, I really can't tell a before and after difference. Maybe if I went back to the T type I might see the difference.

Just to add I've not had any problems will the way the engine idles or runs with the SC grind cams.

earlyaircooled · 02-16-2009, 02:28 PM

The 74 t has smaller intakes and lower compression as I undestand it and different cams than a 74S. Are the valves different also? Did you change everything over to S?

afterburn 549 · 02-16-2009, 02:40 PM

I did this..They come on sooner and pull longer
But..20 20 hind site. If you look in the tech articles some one did a in depth deal on 964 with CIS and arrived @ 200 HP !! They might have moved the C/R up one too.
But for the buck......pretty good bang and keep Reliable CIS to boot

earlyaircooled · 02-16-2009, 02:44 PM

after burn, when you said, "I did this" do you mean SC cams in an otherwise stock 2.7 CIS? If so then it sounds like you did feel more power, right? Seat of the pants feeling anyway?

Thanks,

David

afterburn 549 · 02-16-2009, 03:00 PM

It dyno 155 Hp with 155 TQ at 5300 RPM on that day (at the rear weheels)
It pulls better through out..not as tweeky where it whips you at 3000 rpm
It was a good choice
If I was staying N.A. I would consider a sort of 964 cams with a bump in the c/r
But as soon a s I get a minute I am going to be artificially aspirated ..so there for I retained the 8.5 c/r pistons

4sd911 · 02-16-2009, 04:35 PM

My engine had a top end done before I bought it the PC's were replaced with an S set that have the A2 marked on the piston. I replaced the heads and intake runners to the larger port. Stock T heads can be opened up to the S size. Valves are the same on both type. The S cams were reground by Elgin.

afterburn 549 · 02-16-2009, 04:48 PM

Go way up to the top and look for extracting power from CIS by Noah P (Under tech articles )
just glanced @ it 230 HP !!!! Man O Man, hard to beat for the $$$$

Eagledriver · 02-16-2009, 08:43 PM

If you look at the specs for the cams in question (73tCIS, 74S, and 78on SC), They get progressively "hotter" as you move up. They each have more duration and overlap than the previous one. None could be called a high performance cam. If you have a 2.7S engine with the 35mm ports then you will get improved performace at all RPM from the SC cams. Porsche seemed to get more and more adventurous with the cams as they found what the CIS could take. About the best you can do with CIS pistons is a 964 cam followed by the cams mentioned above.

-Andy

earlyaircooled · 02-16-2009, 10:36 PM

good info so far,

Thanks

afterburn 549 · 02-17-2009, 07:18 AM

True.we all know the flapper plate will not take or like the "reversion" for some reason

earlyaircooled · 02-17-2009, 07:45 AM

I read the 2.7 upgrade tech article by Noah. He went to 9.5:1 JE pistons which I'm sure helped quite a bit. I'm going to use and rering an excellent Nikasil 8.5:1 set that I have. From what I've heard here sounds like the SC cams will help increase performance, that and the 74 and early exhaust back date. Anything else I can do?

afterburn 549 · 02-17-2009, 08:22 AM

Yes, to realize the above benefits you will have to bump the c/r
Otherwise it will be improved.....I forget the formula , but for every bump in c/r = so much HP is attained