When it comes to accurate, reliable and adjustable camshaft timing it is
impossible to go past a quality toothed belt drive system. Fitting one,
however, is often not as simple as making the decision to buy one. Leon
Withnell from A1 Hi Performance in Myaree, takes us through the installation
of an adjustable belt drive being fitted to a 347 Windsor.
There are several advantages to running a toothed timing belt system. The
first is longevity. In most cases these flexible belts will outlast even a doublerow timing chain, particularly in roller cam applications were high valve
spring loads must be overcome to rotate the camshaft. Because the belt is
flexible, rather than rigid like a chain or gear, it does not transmit the
harmonics of the crankshaft into the camshaft. These harmonics can cause
significant vibrations which can de-stabilise the valvetrain. The use of a third
tensioning pulley also ensures higher belt tension for less play and greater
timing accuracy than many chains can offer. Finally, due to its very nature,
the inner section of the cam pulley can be moved in relation to its outer
section which enables the cam timing to be altered very easily, even if the
engine is in the car. These kits initially appeared on US Pro Stock engines
but now they are available for almost any engine.

1. Before the timing kit even sees the light of day, Leon takes special care to
examine the oil delivery path for the thrust surface of the camshaft. Early
Windsors and SVO blocks (like the one in the photos) have no provision for
oiling the thrust face at all. Clevelands have a tiny oil hole just to the side of
the cam tunnel opening. In the case of this SVO race block, Leon grinds a
small slot into the bottom of the cam bearing that intersects the oil supply
hole and allows some oil to flow forward to lubricate the camshaft thrust area.
While on the topic of cam bearings, Leon also performs another minor
modification to bearings not already equipped. By drilling two small holes in
the upper section of the bearing and then placing the shell in a lathe and
turning a shallow groove around the entire outer circumference of the
bearing, oil supply is tripled. If the engine should suffer a brief moment of oil
starvation, it is possible to wipe the white metal off the bearing surface and
block the bottom feed hole. But, if the two upper holes are drilled and
connected by the milled groove, there is enough oil supply remaining to
prevent a major failure.

2. Before the kit could be installed, two small locating dowels had to be
machined to accurately position the alloy housing on the block. Beforeactually bolting the main housing into position it important to check the end
float on the camshaft to make sure it has the desired amount of travel.
An absence of end-float will not allow adequate lubrication of the thrust area
which will result in severe galling. When these tolerances have been
checked and adjusted if necessary, the front cover can be bolted into
position, once the camshaft is installed. Before pressing the crankshaft
pulley onto the crankshaft, apply a little sealer to the pulley’s inner surface
and some oil to its outer surface.

Step 1	Step 2

3. Next, the camshaft pulley and belt are installed. The inner section of the
pulley locates on the camshaft dowel and the outer section is lined up
“dot-to-dot” with the crankshaft pulley. Note, at this point it is advisable to line
the marks on the cam pulley to zero advance or retard until an initial
camshaft degree check has been carried out.

4. With the belt on and the pulley lined up, the tensioner pulley can be bolted
into place. In this kit, there were two of these pulleys, one larger in diameter
than the other. Naturally, the larger diameter would make the belt tighter and
this is particularly useful for blocks that have been line-bored which
effectively raises the crankshaft slightly in the block and requires a shorter
belt or chain. This pulley has a sealed bearing which does not require a
direct oil supply.

Step 3	Step 4

5. Once the kit is installed, the camshaft timing must be checked using a dial
gauge and a degree wheel. Then, if necessary, the six locking nuts can be
loosened and the camshaft advanced or retarded by the required amount for
maximum power and torque. Better still; the camshaft timing can be adjusted
at a later stage, perhaps at the race track or on dyno, to give more bottom
end torque or top end power.
Leon assured us that with a little patience and some thought, such an
installation could be carried out by any competent engine enthusiast. Once
fitted, this is the ultimate cam drive system, and you can’t beat perfect timing!

Step 5	End Result

Re-printed from Volume 14 Number 1 of Perth Street Car Magazine with permission.