| PORSCHE 924 -
NORMALLY
ASPIRATED (N.A.) |
|
Cam
Profile
|
Seat
Duration, .015"
|
.050"
Duration
|
Cam
Lift*
|
|
Stock
046 cam
|
255°
|
223°
|
.472"
|
|
Improved
Stock
|
260°
|
225°
|
.478"
|
|
Stage
1
|
268°
|
232°
|
.500"
|
|
Stage
2
|
276°
|
239°
|
.520"
|
|
Stage
3
|
284°
|
248°
|
.538"
|
|
Stage
4
|
290°
|
254°
|
.548"
|
| PORSCHE 924
TURBO (931) |
|
Cam
Profile
|
Seat
Duration, .015"
|
.050"
Duration
|
Cam
Lift*
|
|
Stock
046 cam
|
255°/255°
|
223°/223°
|
.472"/.472"
|
|
Stage
1
|
268°/260°
|
232°/225°
|
.500"/.478"
|
|
Stage
2
|
276°/268°
|
239°/232°
|
.520"/.500"
|
|
Stage
3
|
284°/280°
|
248°/242°
|
.538"/.520"
|
|
Stage
4
|
290°/284°
|
254°/247°
|
.548"/.525"
|
*
gross cam lift with zero valve lash.
All of the Turbo cam specs are listed as "intake/exhaust".
The normally aspirated (N.A.) Improved Stock cam is designed to be a
mild warm-up over the original stock cam. It is intended to
be a replacement for the stock cam when someone just wants a really
nice running stock motor. A more modern cam design technique
enables better valve control at higher rpms. Additionally,
the slight increase in area under the curve also gives some extra
performance over the stock cam. The idle quality is identical
to the stock cam since there is such a small difference in seat
duration.
The Stage
1 cams are a hot street
performance grind. There is no loss in low end torque with
most of the gain in the mid-range thru top range RPMs. Since
it is ground on a new billet, it bolts in just like a stock cam.**
The Stage
2 cams are designed for an
engine that has a free flow exhaust system. There is a slight
loss in low end torque but a bigger gain in mid-range and top end power.
The Stage
3 cams are designed for an
engine that is driven on the street and also used for club race
events. The large gain in mid-range and top end power to 7200
rpm make it ideal for road racing. This cam is intended for
modified engines running higher levels of boost and that are driven
hard and spend most of their time in the 4500-7200 rpm range.
The Stage
4 cams are designed for race
only use.
**Ideola's
Note: MegaCycle Cams has
purchased the intellectual property from Integral Cams, and do NOT
grind cams on new billet. Rather, they use a weld-and-regrind method to
preserve the original cam circle. Consequently, (and unlike the cheap
regrinds available from WebCam and others), the MegaCycle hard-faced
cams bolt in just like your stock cam, without requiring lash caps like
the cheap regrinds of old camshaft cores. Ideola's Garage is the exclusive
reseller
of Integral Cams' 924 profiles through MegaCycle.
Break-in
Procedure
Set the initial cold valve lash
at
.011" intake / .011" exhaust. After the initial break-in period is over
(see below), check the hot valve lash. Allow the motor to cool down and
then adjust the cold lash by your measured cold-to-hot delta so that
the valve lash will grow to .015" when the engine is hot. It is the hot
valve lash that really matters.
Break-in the new cam at 2000 RPM or slight higher for 20 minutes
continuously after the motor is first started with the new cam.
Detailed
Specs for 931 Stage 1 Cam
We
have not been able to procure all of the detailed specs for the various
profiles, but these are the specs we have from the Stage 1 cams that we
are running in three of our cars, as originally provided by Integral
Cams:
Seat
duration*: 268° / 260°
.050" duration**: 232° / 225°
Gross cam lift: .500" / .478"
Hot valve lash: .015" / .015"
Net valve lift: .485" / .463"
* with .015" hot valve lash
** with zero valve lash
Lobe separation angle = 112°
At
.015" hot lash:
Intake opens 22.0° BTDC
Full intake lift at 112° ATDC
Intake closes 66.0° ABDC
At
.015" hot lash:
Exhaust opens 62.0° BBDC
Full exhaust lift at 112° BTDC
Exhaust closes 18.0° ATDC
Max. RPM = 6500 with stock valve springs at sotck installed heights
with stock lifters
Intake
: Outer Spring : Inner Spring : Total
Valve open : 50.5 lbf @ 1.667" : 11.5 lbf @ 1.555" : 62.0 lbf
Valve closed: 196.1 lbf @ 1.182" : 36.8 lbf @ 1.070" : 232.9 lbf
Exhaust : Outer Spring : Inner Spring : Total
Valve open : 50.5 lbf @ 1.667" : 11.5 lbf @ 1.555" : 62.0 lbf
Valve closed: 188.2 lbf @ 1.204" : 35.4 lbf @ 1.092" : 181.6 lbf
