Stock 2.7CIS w/Webers. What gives?

[farleyd]

I am thinking of fitting my webers on a quite stock 2.7 CIS 1976 w/CIS pistons
What would that do?
Will run with 914-6 headers.

Know about 90mm RS but all the other parts for the conversion scares me a bit. Is there some other 90mm p/cs sets around for use with Webers?

Thanks!

[Joe Bob]

Probably just want to get some hotter cams....doing P/cs is a big job....

[RarlyL8]

Fitting Webers on a stock CIS engine will give you increased throttle response and maybe 10 more true horsepower. The butt dyno will tell you it feels even stronger.

Back dating the exhaust will make the Webers work even better.

Changing the pistons and cams will add real power after adding the carbs and headers.

[TimT]

you will get more power, and it going in a 914 right?

any sellers of suitable 914 chassis please let me know

[Chuck Moreland]

Originally posted by mikez
Probably just want to get some hotter cams....doing P/cs is a big job....

You'll be limited to a mild cam if you don't change the pistons. The CIS pistons don't provide much valve pocket.

[Joe Bob]

My 3.0 really woke up with 964 cams...I even kept the CIS....

[slammed1000]

964 cams are the hottest cams you can get for your combination unless you go into the motor. backdate the exhaust and be happy with the webers. you will see 25-30 hp gain with the ehaust and carbs. 964 cams are a waste of money for 10 hp in my opinion. if you are going to change the pistons you need to bump up in compression and then you can add some big cams. you will see some real power gains after that forsure!

[farleyd]

Here is the answers. Looks like they are Mahle 90mm Nikasil 8:5.1 p/c set offered by Performance, with that caption (please dont laugh....):
- - -
High performance pistons and cylinders
911 2.7 Nikasil 8.5:1 A911.103.928.01
Increase the torque of your Porsche´s engine, have more driving fun, and better gas mileage with European high performance piston. While the compression ratio in some cases is the same as US standard pistons, there is inceased performance because the piston tops are shaped for more efficient fuel-air distribution and more power.
- - -
Marketing hype?

OPTIONS AS WE SPEAK

What would be the difference between these two options:

- CIS pistons (be they marketing hype or stock), CIS cams and Webers and 914-6 headers
OR
- JE pistons 9.5:1, E-cams and Webers and 914-6 headers

THAT answer will gte me to it.

Many thanks!


or

[jluetjen]

Farleydw;

Those pistons that you have are definitely some form of CIS pistons. If you used those with 964 cams and the stock CIS system, I would expect that you could get about 190HP at 6200 RPM and 172 lb-ft of torque at 4900 RPM. I suspect that they will have the same issues when used with Webers as stock CIS pistons. If you want to change the pistons to MFI/Carb style pistons, then going with Webers and E or S cams will most likely get you over 200 HP depending on the exact configuration.