SPITFIRE MkIV & 1500

CYLINDER HEAD & COMPONENTS . VALVES . GUIDES . ROCKER GEAR
22
Performance
& TUNING
Cylinder Head & Components
On all Triumph engines, the cylinder head must be gas flowed properly to
maximise the performance & efficiency from the engine.
Special note for 948/1147 Cylinder Heads:
The cylinder head on the (948/1147) 6 port engines has been fitted with a
number of different size valves during the production run. The Herald
models were always fitted with a larger valve than the Spitfire models,
although these were also of the ‘slide in’ type of valve cap (not
recommended). All the modifications are based using the largest valves
and to the ‘flow rig designed’ chamber/ports profile. Our heads are
supplied ready assembled with new valves, TT springs and new guides.
Work on the cylinder head centres around making the best diameter of the
inlet port to suit and give maximum power potential. We have found that
increasing the size of the Inlet Valve to 1.475" and very careful flowing of
chamber/valve throat area will produce good torque and allow top-end
breathing for sprint/racing use. The increase in exhaust valve size
(competition use only) improves the flow of the port for maximum power.
All heads are supplied ready assembled with new valve springs & guides.
The cylinder head modifications have been designed using a flow-rig to
obtain the maximum from the head casting.
Valve springs fitted to all our cylinder heads are the best uprated road
specification. They are designed to allow the maximum lift from our
performance camshaft profiles without excessive loads on the cam-lobes.
Spring retainers must be checked - especially the two part version for
cracks. Alloy types are available to save weight whilst still being strong
enough for all applications.
Valves, these are recommended to be gas flowed in the slim design, as
this will improve the efficiency of the modified cylinder head
substantially.
Rocker Gear (General)
For a road car the standard rocker gear only requires minor alterations.
For competition use or maximum power then the use of the roller rockers
will be a major benefit.
By reducing the weight of the moving components in the rocker gear,
followers, valves, caps etc. and also the 'resistance of the rockers', the
rev range can be improved without increasing the loading on the
camshaft.
Valves
TriumphTune reshaped valves are manufactured in the very hard wearing
stainless steel EN214 material.
Valve Guides (Bronze)
Our 'bronze alloy' valve guides are for improved reliability and longer life,
especially when being used under duress. Highly recommended for all
heads and especially for any competition engine. Specially reshaped for
'improved' flow.
Valve Springs
It is essential to check the springs for 'coil binding' or being solid at
maximum lift. Our TriumphTune valve springs are specially made for our
high-lift cams. Remove lower spring collars if TriumphTune springs are
used, as they are no longer required.
Valve Spring Caps (Alloy)
Standard caps are adequate in strength for all applications, but our
TriumphTune 'Light alloy' caps reduce valve loading and therefore wear
on cam lobes. Weight saving is approximately 25%.
Rocker Arm Action
The rocker arm is designed to move across the valve tip in a wiping motion,
this leaves a witness mark on the stem top. To be certain your engine
geometry is correct, remove the rocker arm and apply some 'Engineers
Blue' to the valve tip and rotate the engine through one revolution with the
rockers correctly adjusted and the engine in its final specification.
Remove the rockers and the valve tip will show the offset of the rocker
geometry.
Centre'
This is correct equally offset, so no excessive wear on either side of the
guide will be found.
Manifold Side'
If the mark is predominantly on this side, then the push rods and/or the
pedestals must be shortened to correct this. (With the wear on this side
there will be excessive loading on the valve guide that will cause
premature failure)
Rocker Side'
If it is to this side slightly, then this is no problem. But, if it is a along way
off, then you can fit a pedestal spacer shim (TT1910) to compensate, or
alternatively, fit longer push rods.
Alternatively use
TriumphTune
(shortened) push
rods.
Pedestal Shim - TT1910
Note: Do Not use lower spring collars with the inner
springs when fitting TriumphTune valve springs.
Clearance of 0.09"
needed here
BRADFORD 01274 735 537 . BRISTOL 0117 923 2523 . DARLINGTON 01325 281 343