| |
|
Reciprocating
Assembly |
|
| |
RPM |
Engine
Use |
Engine
Life (A)
Approximate Hrs./Miles |
(B)
Piston to
Cylinder |
Rod
Bearings |
Main
Bearings |
Starvation
Protection |
(F)
Pressure
(In lbs.) |
Temp
°F |
Pressure
(In lbs.) |
(H)
Total
Mass |
Piston
Type |
Wrist
Pin
Type |
Rod
Type |
(I)
Rod
Ratio |
(J)
Compression
Ratio |
(K)
Bore/
Stroke
Ratio |
(L)
Stroke
Maximum |
(M)
HP/
Torque
Ratio |
(N)
Rear
Gear
Ratio |
 |
9000 |
- Drag Race |
1 hr
75 miles |
.0050
.0060 |
(C)
.0022
.0024 |
.0025
.0027 |
Scrapper Bar
Windage Tray
Cornering
Baffle
(D) (E) |
90 lbs. |
230°F |
(G)
20 + lbs.
with a 5/8"
Restrictor |
1000
grams |
Very
Lightweight
Forged
Alusil
390-415 grams
|
Tool Steel
75 grams |
Aluminum
525 grams
Titanium
490 grams |
1.9 |
14:1
to
12:1 |
1.20 |
67mm |
1.60
to
1.45 |
5.89
5.29 |
| 8000 |
- Full Race
- Circle Track
- GT Racing |
4 hr
300 miles |
.0040
.0050 |
.0021
.0023 |
.0024
.0026 |
80 lbs. |
220°F |
20 + lbs.
with a 3/4"
Restrictor |
1125
grams |
Steel
115 grams
|
Steel
4340 alloy
635 grams
|
1.8 |
12.5:1
to
11:1 |
1.15 |
75mm |
1.45
to
1.30 |
5.00
4.75 |
7000 |
- Vintage Racing
- Improved Touring
- Driver's Schools |
15 hr
1125 miles |
.0030
.0040 |
.0020
.0022 |
.0023
.0025 |
70 lbs. |
210°F |
20 + lbs.
optional 3/4"
Restrictor |
1285
grams |
1.7 |
11.5:1
to
10:1 |
1.10 |
86mm |
1.30
to
1.10 |
4.27
4.11
3.90 |
|
|
6000 |
Autocrossing |
75 hr
4500 miles |
.0025
.0030 |
.0019
.0021 |
.0022
.0024 |
Cornering
Baffle |
60 lbs. |
200°F |
15
lbs. |
1500
grams |
Lightweight
Forged
Alusil
420-450 grams |
Steel
100 grams |
Lightened
Stock
650 grams
Stock
710 grams |
1.6 |
10.5:1
to
9:1 |
1.05 |
100mm |
1.10
to
.95 |
3.73
3.64
3.46 |
5000 |
Hard Street Driving |
500 hr
30,000 miles |
.0020
.0025 |
.0018
.0020 |
.0021
.0023 |
50 lbs. |
190°F |
1.5 |
.95 |
.95
to
.80 |
3.25
2.93
2.79 |
| 4000 |
Highway
Driving
4 Cylinder |
2000 hr
90,000 miles |
(A)
Calculating Engine Life in Miles
7000-9000 rpm ...hrs x 75mph = miles
5000-6000 rpm ...hrs x 60mph = miles
2000-4000 rpm ...hrs x 45mph = miles
|
|
(B)
Piston to cylinder wall clearance is figured from a Metric Mechanic
high silicon content forged piston with a vented or undercut skirt. |
|
(C)
Because aluminum rods have a much higher expansion rate than steel
or titanium rods, they require only .0015" to .0020" clearance. |
3000 |
Highway Driving
6 Cylinder |
3500 hr
157,500 miles |
(D)
Once the engine speed goes over 7200 rpm, the #4 main bearing needs
to be modified in order to increase oil flow to #3 & #4 rod
bearings. |
|
(E)
Also, the cam sprayer bar "banjo" bolt needs to be restricted
off to prevent excessive oil flow from flooding the cam. The banjo
bolt receives a .074" restrictor hole up to 7500 rpms. For
rpms higher than this, use a .062" restrictor hole. |
|
(F)
The maximum hot oil pressure for a stock engine is about 64 lbs.
To go above this, we install Metric Mechanic oil pressure relief
valve shims. Each shim represents an 8 lb. increase in oil pressure. |
| 2000 |
Highway
Driving
Late 6 Cyl.
with 5sp |
5000 hr
225,000 miles |
(G)
To increase coolant pressure in the heat at higher rpm, a restrictor
is placed in the upper radiator hose. A 3/4" restrictor hole
is used from 7000 to 8500 rpm and a 5/8" restrictor hole is
used from 8000 to 9500 rpm. A 22 to 24 pound cap should be used
at these higher rpms. |
|
(H)
Maximum reciprocating mass can be calculated by the following formula:
9,000,000 = Total Mass in Grams
max rpm
The piston assembly (piston, pin, rings & clips) should be at
least 10% lighter than the rod to maintain adequate rod life. |
|
(I)
Rod Ratio is defined as the length of the rod (from the center of
the big end to the center of the small end) divided by the stroke
of the engine. To figure the proper rod ratio for a given rpm, add
1 and a decimal point "1." in front of the maximum rpm
for the engine. For example, the correct rod ratio for an 8000 rpm
engine would be 1.8000. |
| |
(J)
The reason compression needs to go up with rpm is that as rpm goes
up, the duration of the cam must be increased. The longer the duration,
the later the intake valve will close off and this lowers the static
compression of the engine. |
|
(K)
Engines with bore/stroke ratios greater than "1" are commonly
referred to as over square engines while engines less than "1"
are considered under square. |
|
(L)
The formula that we use to calculate maximum stroke for an engine
is:
600,000 = Maximum Stroke
max rpm |
(M)
Engines with a horsepower/torque ratio of less than "1"
are considered "torque" engines, while engines with a
ratio greater than "1" are horsepower engines. For us,
we build our street engines (the MMiFlo ST Sport Series) with a
close balance between torque and horsepower. Our rally engines for
driver's school use, are more in line with BMW's M engines where
the horsepower is about 10% to 30% greater than the torque and in
our race engines, the horsepower is about 50% greater than torque. |
|
(N)
The rear gear ratio should be looked at as the engines torque multiplier. |
Next
Up