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2.7 - 165hp vs 175hp

What is the difference between the 175 and the 165 hp engines?

I have the 165hp engine and is wondering if it can be modified to the 175 version without to much work.
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Magnus
911 Silver Targa -77, 3.2 -84 with custom ITBs and EFI
911T Coupe -69, 3.6, G50, "RSR", track day.
Old 08-20-2004, 11:01 AM
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Magnus, why would you bother going that route? In Bruce Anderson's book, he decribes taking a 2.7 CIS engine and changing to RS pistons, E cams, Webers, and SSI heat exchangers and you end up with a near 2.7RS MFI level of performance.

Disclaimer: There's a lot about this stuff I don't know so my advice might be off the mark. Also, I'm not factoring in any specific budget you might be working with.

Best wishes on whatever you end up doing.
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Old 08-20-2004, 11:50 AM
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I believe there is a bump in compression, but FOR SURE the heads have much bigger ports (35/35mm) and the cams are more radical (as radical as CIS can get...). You will need to at least change your heads to 2.7 911S heads or port yours to whatever you want, and the 2.7 911S heads are close to RS specs (36/36mm) so that's the cheapest way of going about it. Changing cams, you can of course run 911SC/964/2.7S/ Webcam 20/21? but I don't know a whole lot about those kind of cams. If you want to run say early 911E, solex or 911S cams, you have to change your pistons and go to carburetors or MFI. It gets involved right there. But if your motor is already apart/down, you should be able to get about 180 out of it with easy stuff (keep CIS, go to 2.7S heads, maybe 2.7S cams etc.)
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Old 08-20-2004, 05:07 PM
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If I read this right he has a 165hp 2.7 which would be a 75-77 CIS "S" motor. the difference between that and the 175hp 2.7 from 74 (also ROW 75-77) is the exhaust.

so to answer your question if you change your exhaust to the early (pre 74) heat exchangers you will have the same package as the 175hp engines.

the non "S" 2.7 w/ 8.0:1 compression and small ports was only rated for 150hp
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Old 08-20-2004, 09:34 PM
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From what I have read, and been told if you put SC grind cams in and bump your compression up to 8.5:1 if it isn't already there you should get 175hp. This is what I am doing for my '74 2.7.
Good luck!
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Old 08-20-2004, 11:03 PM
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If you decide to go with the SC profile cams I have a fresh pair still in the box (never opened). These are CIS cams with an SC profile (slip right in).

Intake duration @ 1mm is 236 degrees valve lift is 450"
Exhaust duration @ 1mm is 224 degrees valve lift is .395"
set up at 1.4-1.7 mm
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Old 08-20-2004, 11:21 PM
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I have been reading up on Waynes book and the engines seem to be identical for compression, camshafts and timing.
The only difference must be the pre 74 exhaust, that must also has been used on the 75 RoW 911S.


My engine is not in need of rebuild yet (100k), but when it is I will probely go with the RS pistons, s-cams and carbs (or maybe efi). In the meanwhile I could upgrade to SSI.

Thanks for your response!
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Old 08-22-2004, 03:32 AM
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I would like to ad my 0.2 cents.. As I have just completed a complete restoration on my 1975 911 Carrera (2.7 us). Including body, interior, engine and trans.

ENGINE:
-New RS Pistons (Forged)
-Webcam SC profile hard weld and regrind
-Heads fly cut
-compression is now 9:5
-SSI's and Dansk muffler
-Everything in the fuel system from the gas tank to the injectors is brand new including airbox
-SC throttle body
-Case wase machcined and updated by CE
-Sachs sport clutch
etc, etc, etc...$$

The car screams and is very smooth. It pulls hard straight up to redline. I will be taking it for a dyno soon. Far exceeded my expectations



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Old 08-24-2004, 02:22 PM
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what is the diameter of the SC throttle plate?
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Old 08-24-2004, 03:48 PM
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Alan, Sorru but I don'r know the diameter. I'll ask my wrench. It's seems bit larger than the 2.7 with different shape cone.
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Old 08-24-2004, 04:34 PM
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Carreric, a very nice looking car!

Can you use Carrera RS pistons with CIS injection? I thought you needed the special cis-pistons for it to work.
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Old 08-25-2004, 01:27 AM
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That was my thinking, too. I was expecting to see Webers on that engine.
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Old 08-25-2004, 04:32 AM
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Quote:
Originally posted by safe


Can you use Carrera RS pistons with CIS injection?
BTDT
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Old 08-25-2004, 06:13 AM
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Ron, you're running Webers with RS pistons now, right? How'd it work with RS pistons and CIS? Was that the setup you had when you took me out for a spin on LI?
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Old 08-25-2004, 06:49 AM
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Yes the car runs great with RS pistons, very smooth and strong. When my wrench disssembled my engine the original CIS pistons were in good shape. However I wanted everything new. I decided on RS pistons for a few reasons - They were forged not cast like CIS (stronger piston), future option to use webers, Price new was the same as CIS.

Overall I feel the car runs better with the RS pistons.
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Old 08-25-2004, 06:51 AM
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But you must loose something with RS pistons (like smog or mileage) otherwise why use CIS pistons? I thought they where designed to help atomize the fuel.

Carreric: Did you reuse your cylinders, alusil or nikasil?
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Old 08-25-2004, 07:38 AM
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Safe, Probably loose both smog and mileage. But not concerned about smog in Miami (no emissions). I also understand CIS was used in large part for emissions. I didn't reuse cylinders. Bought new RS pistons and cylinders.
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Old 08-25-2004, 12:08 PM
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Quote:
Originally posted by Jim Richards
Ron, you're running Webers with RS pistons now, right?

How'd it work with RS pistons and CIS? Was that the setup you had when you took me out for a spin on LI?

PMO

yep.. you rode with CIS & RS pistons. No smog check prob.. although if mix setting is on low side of specs it may bog a little off the line. I'm not sure if it was caused by RS pistons? The RS pistons is a really brainless replacement for the stock pistons. Stock pistons wear much more than the RS and probably are in good shape for only 100k miles. I don't have that experience, it's what I read somewhere.

PS: cross country millage with RS & CIS maxed about 25-26mpg.
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Old 08-25-2004, 12:15 PM
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OK Ron. It's nice to come here and learn new things every day.
My butt dyno says that this combo is a lot of fun.
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Old 08-26-2004, 05:35 AM
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