Part one

Selecting the correct camshaft

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 Pty Ltd (I.T.E) have invested in three (3) of the latest technologies available to ensure the best options in both camshaft and engine design are explored.

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 vechile. The engine may have different characteristics but produce the same horse power (H.P)

EXAMPLES

This range is designed for bottom end, better economy and better throttle response designed for a standard engine. If an engine has been modified this range of camshaft will still perform well but wider lobe centers 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 110* - 113*.

Power range:
Small capacity 1850 - 5200 R.P.M
Large capacity 1250 - 4500 R.P.M

This range is designed more for the midrange, smooth cruise and slightly lopy idle. This is still suitable for automatic transmission using standard stall converter. Modified Distributor and exhaust systems are recommended. This is good for towing in larger capacity engines. Higher compression ratio is not required, larger valves are not recommended. A typical lobe separation is 108* - 112*.

Power range:
Small capacity 2000 - 5800 R.P.M
Large capacity 1500 - 5000 R.P.M

This range is for modified street, limited modification race or speedway. Used for single carburetor (350 Holley) and 6 cylinder engines. Twin carburetors are recommended for 4 cylinder engines.
For road application suggest ported cylinder head, bigger valves, balancing and higher compression ratio (9 or 10:1). The distributor also requires regraphing. Lopy idle, if automatic transmission is used a higher stall will be required. A wide area of camshaft selection, different duration's and lobe centers used are to give different power ranges. Lower rear axle ratio may be required to achieve the best result from these modifications.
Typical lobe separation of 106* - 110*.

Power range:
Small capacity 2600 - 6500 R.P.M
Large capacity 2200 - 6000 R.P.M

Note: Valve spring retainers must be checked for suitability, depending on piston choice. Valve to piston clearance will also require attention.

This range of camshaft are more for an engine designed rather than for camshaft replacement. The engine must be designed and built with the design of the camshaft in perspective.

- Multiple carberation is recommended for both 4 and 6 cylinder engines.
- Minimum of 600 - 750 C.F.M carburetors is recommended for V8 engines. The size of the carburetor will depend on the engine capacity.
- Valve springs must be checked for suitability. Harmonic testing is recommended if high R.P.M is to be used.
- High compression recommended achieving the best performance a ratio of 10-11.5:1.

Typical lobe separation of 100* - 106*.

Power range:
Small capacity 4200 - 10000 R.P.M
Large capacity 3700 - 8500 R.P.M

Part two

Points to keep in mind when selecting your camshaft

The following are remarks intended to help you to select the correct camshaft. If you have a camshaft that works well in one type of engine this will allow you to adapt it from one engine to another.

" If the cylinder head is flowing more (has been ported) the lobe centerline can be closed. This will give the best benefit of the improved airflow.

" If the capacity of the engine is smaller the lobe centerline will be opened to achieve the same results.

" The exhaust profile is much less critical on low compression engines. I.T.E recommends a smaller exhaust profile on low compression small engines.
" It is highly recommended that for best results that flow figures for the cylinder heads are used. This helps give the engine the correct balance inlet to exhaust.

" The closer the lobe centerline the harder the engine will "come on the cam". I.T.E use wider lobe centerlines on speedway applications for this reason.

" If a hydraulic camshaft is being replaced with a solid camshaft the .050" duration needs to increase by 8* or 10* to obtain the same effective duration.

" For every 10 CI (200cc) the duration needs to be increased by 1* at .050" to have the same effective duration. This is more effective in V8 engines rather than 4 cylinder engines.

" The inlet profile has more influence on the power range than the exhaust. Most of the higher performance 4 valve engines have a larger inlet than exhaust. A difference of up to 10*-12* is not unusual when using a retarded exhaust camshaft.

" 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.

" The camshaft designers in the USA use the large exhaust concept to sell the customer the camshaft required. The camshaft does not have a larger exhaust, but a smaller inlet profile. This allows the camshaft to be solid as a 280* duration but has the characteristics of a 270* camshaft."