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Burtons do not recommend installing a performance camshaft in a vehicle fitted with
an automatic gearbox.
The installation and first few moments of running are critical factors in the life
of the camshaft. Failure to install the camshaft correctly will have a drastic effect
on the life of the camshaft and in the worst cases can result in immediate failure.
The following instructions must be adhered to in order to obtain maximum performance
from the engine and to ensure a long and trouble free life from both camshaft and
associated components. These instructions are also provided in addition to the original
manufacturers installation procedure. Where a camshaft is being replaced due to
excessive wear, it would be highly recommended to strip the engine and fully clean
the internals. Metal particles present in the sump, oil pump, bearings and oil galleries
will soon play havoc with the new cam. It would also be wise to check the oil feed
system. Low oil pressure due to a worn pump, blocked pick-up pipe or blocked oil
galleries will quickly wear the new cam to the same state as the one being replaced.
In other words, before replacing a failed camshaft, make sure you find out the reasons
for the failure and correct it! Before fitting the camshaft, check that it is identical
in every aspect (with the exception of the lobe profiles) to the one being replaced.
Special attention should be given to the oil feed positions and journal diameters
as variations may occur during the manufacture of the engine. Also check that any
gallery bungs present on the old cam are also in place on the new cam. Do not remove
the black phosphate coating from the new cam lobes. Liberally coat both the camshaft
and cam followers with a proprietary cam lube or engine assembly compound.
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At Burtons, we recommend and use Graphogen, a colloidal graphite paste. Failure
to do this can cause scuffing between the surfaces of the cam and followers, which
will result in premature wear. Ensure that followers are free to rotate in their
bores where applicable. It is essential that new followers are always fitted, regardless
of the condition or limited use of the old followers. Failure to do so may cause
premature components failure and consequently will invalidate any warranty claim.
Upon installation, the valve springs must be checked to ensure that:
i) the fitted length (installed height) of the valve springs match the figure provided
by the manufacturer (see fig. 1). If too small, then the valve seat areas in the
head will require machining. If too large, shims can be added to the spring seat.
Due to varying manufacturing tolerances of cylinder heads, all springs should be
checked and measured for clearance.
ii) coil binding does not exist at full valve lift. This is the condition where
the spring is fully compressed (see fig. 2). As a guide, at full cam lift the spring should be able
to compress a further 0.060” (1.5mm) before the coil bound condition is reached.
This can be checked by inserting feeler gauges between each coil of the spring and
adding the results together to get a total clearance figure. Due to varying manufacturing
tolerances of cylinder heads, all springs should be checked and measured for clearance.
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Check the clearance between the bottom face of each retainer and the top of the
guide or stem seal at full lift (see fig. 2). This should be a minimum of 0.080”
(2mm). If this clearance cannot be achieved, the top of the guides must be machined.
When double valve springs are being installed in place of singles, ensure that the
inner spring is correctly located and the correct retainers and platforms are used
where applicable.
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When modifying engines that utilise finger followers i.e. SOHC Pinto, it is imperative
that you ensure the followers remain in the original attitude relative to the cylinder
head. Failure to do so will alter the rocker geometry, increasing or decreasing
valve lift and can result in failure of both cam and followers or excessive valve
stem/guide wear.
For OHV engines, attention should be paid to rocker arm geometry for the same reasons.
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Rotate the crankshaft clockwise to 90 degrees after TDC. This will make sure all
the pistons are half way down the bore. Now position the dial gauge so that it can
read the lift of the inlet valve of number 1 cylinder from the top of the valve
retainer (see left). Rotate the cam until the gauge shows that the valve is at full lift. As
with the crankshaft, there will be a dwell period where the valve is at full lift.
True full lift is at the centre of this dwell period. Roughly position the cam at
true lift position. Now rotate the crankshaft clockwise to the full valve lift position
(as specified on the camshaft data sheet - this figure is typically from 100 to
120 degrees after TDC), fit the timing belt or chain and set up the tensioner.
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Now rotate the crank clockwise until the inlet valve of number one cylinder
is just off full lift position (such as 0.005” or 0.15mm). Record the figure on
the timing disc from the pointer. Then continue to rotate the crank clockwise until
the valve has fully opened and then closed by the same distance as previously used
(0.005” or 0.15mm). Read the figure on the timing disc again. The position of full
lift is the middle of these two figures. The full lift position can be calculated
by adding the two figures together and dividing by two. Adjustments can then be
made to the camshaft timing, using an adjustable cam pulley or offset dowels, if
this figure does not agree with the one on the data sheet. Check the timing again
after adjustments using the same procedure. Having timed the camshaft, check that
there is no piston to valve contact. Minimum clearance is 0.060” (1.5mm). This can
only be checked by dummy building the engine with a piece of Plasticine placed on
the crown of the piston. As the engine is turned, the valves will indent the Plasticine.
The clearance is then measured as the thickness of the Plasticine between the piston
crown to the bottom of the valve indent. Before starting the engine, turn the engine
over by hand to ensure that it turns freely. Prime the oil system and check that
everything is set to ensure that the engine starts straight away. The engine must
not be turned over for any length of time on the starter. Once started, do not allow
the engine to idle for the first 20 minutes and keep the revs to a minimum of 2500
rpm. This will ensure adequate lubrication of the cam and followers and reduce the
contact force between the cam and follower. If any adjustments need to be made within
the first 20 minutes, then shut the engine down. Do not allow the engine to idle.
Please note that new hydraulic lifters may in some cases operate with excessive
noise for a few minutes before they are fully charged with oil.
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