This section is designed to help in selecting the correct
camshaft for your engine. There are many different programs
available on camshaft selection Ivan Tighe Engineering are
currently investigating these programs. The programs tested
are very accurate if a Chevrolet V8 is the test engine, but
if a 16v Suzuki is tested, in particular parameters the
selection does not work on the dynometer.
The most important thing to remember is that there are 2 or 3 different
profile combinations that will have identical results in an engine,
particularly in a road driven vehicle. The engine may have different
characteristics but produce the same H.P. & Torque.
250º - 264º
|
Advertised Duration.
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195º - 210º
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0.050" Duration.
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This range is designed for bottom end, better economy and
better throttle response designed for a standard engine, if
a engine has been modified this range of camshaft will still
perform well, but wider lobe centres may be required to
achieve best results.
Suitable for towing and heavy-duty applications, smooth
idle, high vacuum for both auto and manual use. Typical lobe
separation of 1100 - 1130
Power Range:
Small Capacity
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1850 - 5200 R.P.M.
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Large Capacity
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1250 - 4500 R.P.M.
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264º -
272º
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Advertised
Duration.
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210º -
225º
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0.050"
Duration.
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This range is designed more for the midrange, smooth
cruise and slightly lopy idle. Still suitable for automatic
transmission using standard stall converter. Modified
Distributor and exhaust system recommended. Good for towing
in larger capacity engines.
Higher compression ratio not required, Larger valves not
recommended.
Typical lobe separation 108º - 112º.
Power Range:
Small Capacity
|
2000 - 5800 R.P.M.
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Large Capacity
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1500 - 5000 R.P.M.
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272º -
290º
|
Advertised
Duration.
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225º -
245º
|
0.050"
Duration.
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This range is designed for modified street, limited
modification race or speedway. For single carburetor (350
holley), 6 cylinder engines. Twin carburetors recommended
for 4 cylinder engines.
For road application suggest, Ported Cylinder head, Bigger
Valves, Balancing and higher compression ratio (9 or 10:1).
Distributor also requires regraphing. Lopy idle, if
Automatic transmission is used a higher stall will be
required. A wide area of camshaft selection, different
durations and lobe centre lines used to give different power
ranges.
- Lower rear axle ratio may be required to achieve the
best from the modifications. Typical lobe separation of
106º - 110º
Power Range:
Small Capacity
|
2600 - 6500 R.P.M.
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Large Capacity
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2200 - 6000 R.P.M.
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NOTE: Valve spring retainers must be checked
for suitability, depending on piston choice, valve to piston
clearance will also require attention.
300º
+
|
Advertised
Duration.
|
250º
+
|
0.050"
Duration.
|
This range of camshaft is more for engine design rather
than for camshaft replacement The engine most be designed
and built with the design of the camshaft in
perspective.
- Multiple carburetors recommended for both 4 and 6
cylinder engines.
- Minimum of 600-750 C.F.M. Carburetor recommended for
V8 engines, size of carburetor depending on engine
capacity.
- Valve springs must be checked for suitability,
Harmonic testing recommended if high R.P.M. is to be
used.
- High compression recommended to achieve best
performance (Above 10.5:1}
Typical lobe separation of 100º - 106º
Power Range:
Small Capacity
|
4200 - 10000 R.P.M.
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Large Capacity
|
3700 - 8500 R.P.M.
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Points to keep in mind
when selecting your camshaft.
The following remarks are intended to help you
select the correct camshaft, if you have a camshaft that
works very well in one type of engine, this will allow you
to adapt from one engine to another.
- If the cylinder head is flowing more (has
been ported) the lobe centreline can be closed.
This will give the best benefit of the improved
airflow.
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- If the capacity of the engine is smaller the
lobe centrelin~hold be opened to achieve the
same results.
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- The exhaust profile is much less critical on
low compression engines. Ivan Tighe Engineering
recommends a smaller exhaust profile on low
compression, small engines.
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- It is highly recommended that for the best
results, the flow figures for the cylinder heads
are used. This helps to give the engine the
correct balance inlet to exhaust.
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- The closer the lobe centreline the harder
the engine will "come on the cam". Ivan Tighe
Engineering use wider lobe centrelines on
Speedway application, for this reason.
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- If a hydraulic cam is being replaced with a
solid cam, the 0.050" duration needs to increase
by 80 or 100 to obtain the same effective
duration.
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- For every 10 CI. (200cc ) the duration needs
to be increased by 10 at 0.050" to have the same
effective duration. This is more effective in V8
engines rather than 4 CYL. engines.
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- The inlet profile has more influence on the
power range than the of the higher performance 4
Valve engines, have a larger inlet than exhaust
A difference of up to 20º is not unusual.
This gives the engine more flexible power.
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- The exhaust profile can dictate to the
inlet, the exhaust can help the cylinder fill
and clean the combustion chamber on overlap.
This allows more mid range, but with a loss of
fuel efficiency and response.
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- The camshaft designers in the U.S.A. use the
large exhaust concept as to sell the customer
the camshaft they require. The camshaft does not
have a larger exhaust, but a smaller inlet
profile. This allows the camshaft to be solid as
a 280º duration but has the characteristics
of a 270º camshaft, because the inlet has
more influence on the power band.
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