Cam choice for awakening 2.2T

[Pesch]

Hello folks,

In the process of rebuilding a 2.2T with a friend, our cam grinder made us 2 proposition as follow:

Values are given @ 1mm (0.04") lift and 0 lash
Rocker ratio 1.50 (some doubt on that one)

Option 1:
Duration 232/224, lift: 6.75/6.00mm @cam, 10.05/8.94 @valve (0.256/0.236" - 0.396/0.352")

Option 2:
Duration 242/232, lift: 7.35/6.60mm @cam, 10.95/9.38 @valve (0.289/0.260" - 0.431/0.369").

Engine will get 86mm biral cylinders and JE pistons at the same time.

What do you guys think about these values?
Lift looks a bit small compared to duration but I don't have a deep knowledge on 911 cams.

Cheers
Arnaud

[doswald]

Arnaud, the Solex cam has been consistently recommended for your setup. I don't recall the specs, but you should be able to find them quite readily and compare them to your options.

Regards,
dho

[T77911S]

CR is big factor in deteriming what cam to use.
you can "over cam" a low compression engine.

[Pesch]

CR should be around 10.1 to 1

Here's what Dougherty list for the Solex and others:
Model-------------------------Duration @ 1mm-------@ .050"--------Valve lift-------Lobe seperation angle----Lift @ overlap setting
Porsche 911 Solex--I/E------248/236-----------------242/230-------.455"/.414-----97--------------------------4.2-4.6 mm
Porsche 911 E-------I/E------238/226-----------------230/222-------.405"/.393"----102-------------------------3.0-3.3 mm

Low proposed lift is maybe due to the original T cams available "meat"...

Thanks for your input

[BK911]

E or solex cams.
2.4 crank and rods.

[cmcfaul]

DC 30's (mod S) on my 73 E with 10.0/1 CR was awesome and a highly recommended setup. Higher performance cams will have more overlap to help the engine breath. This lowers the compression to some degree (in exchange for volumetric efficiency). This needs to be offset by higher compression pistons (which you have).

Real world experience, the car hit a power-band at 6k RPM'S where it used to run out of breath with the stock E cams.

[Pesch]

Thanks for all the feedback, the point is that our configuration is more or less fixed with the cost in mind:

- original crank
- 86mm cylinders (as original ones are scored)
- slightly ported heads
- dansk heat exchanger
- reground T cams

Here's the proposition from our local cam grinder (in France):
Duration 242/232, lift: 7.35/6.60mm @cam, 10.95/9.38 @valve (0.289/0.260" - 0.431/0.369").

After checking details of different data from well known cam grinders, I think that the intake will be fine but maybe it would better to shorten exhaust duration in order to increase the lift.

What do you think?

[SWS911]

I think with that C/R you should twin plug, and running high RPMs you need a counter balanced crank.