Contents
SPEEDPRO SERIES
Contents
Introduction ....................................6
Using This Book & Essential
Information ..................................... 9
Chapter 1 - Cylinder Block .......... 11
Which cylinder block? .................. 11
Extra head studs & centre main
strapping.................................... 11
Sleeved blocks .............................. 13
Over boring................................... 14
Chapter 2 - Crankshaft ................ 15
Crankshaft checking &
preparation ................................ 16
Thrust washers/endfloat ............... 16
Chapter 3 - Connecting Rods ...... 19
Important component sizes .......... 21
Chapter 4 - Pistons & Rings ........ 22
Cast pistons ..................................22
Forged pistons .............................. 23
Piston to bore clearance ............... 23
Rings .............................................23
Summary ...................................... 23
Chapter 5 - Cylinder Block &
Internal Components
- Checking & Preparation ......... 24
Block .............................................24
Crankshaft ....................................26
Connecting rods ...........................27
Camshaft ...................................... 27
Important component sizes ..........28
Engine balance .............................28
Pistons, rings, piston pins ...............28
Connecting rods .............................28
Crankshaft, damper, flywheel,
clutch cover, pressure plate,
keyplate and nut ........................28
Chapter 6 - Camshaft &
Camshaft Drive ......................... 30
270 degree camshafts .................. 31
1300 MG Metro camshaft .............. 31
731 ................................................31
290 degree camshafts .................. 31
544 ................................................31
Racing camshafts ......................... 32
649 ................................................32
Camshaft drives ...........................33
Camshaft timing ...........................34
Chapter 7 - Cylinder Head ........... 36
Fitting 1300 MG Metro head to
998cc block ...............................36
Avoiding exhaust valve to block
contact .......................................38
Unshrouding inlet valves at bore
tops ............................................41
Compression .................................41
Cylinder head choice ................... 43
Racing engines ...............................44
Unleaded fuel heads .......................45
Obtaining a correctly modified
cylinder head ..............................46
Valve size combinations .................46
Checking cylinder heads modified
by third parties ............................46
Fuel octane rating v. compression
ratio (CR) ..................................48
Note on leaded fuel ......................49
Chapter 8 - Cylinder Head
Porting .......................................50
Inlet ports .....................................51
Inlet ports - area adjacent to
pushrod holes ............................51
Inlet ports valve throats ...............53
3
CYLINDER BLOCK
available from UNIPART singularly or
in a complete gasket set. These
cylinder head gaskets are not
expensive and hold the compression
seal better than any other original
equipment cylinder head gasket by a
considerable margin. Even though
these cylinder head gaskets are for the
1275cc engine, they’re used on high
performance 998ccc engines.
SLEEVED BLOCKS
The two extra head stud holes are arrowed here.
with nine studs go just as well as
engines which have eleven studs, but
the reliability of the cylinder head
gasket will not normally be as good. A
modified road going engine will always
prove to be reliable with nine studs
and up to 10.0:1 compression provided the block and cylinder head
gasket surfaces are truly flat. Caution!
- For high compression (11.0:1 plus)
racing engines using nine stud heads,
always replace the head gasket every
200 racing miles and always have a
spare cylinder head gasket for
immediate replacement.
The most common point of
gasket failure on a nine stud engine,
irrespective of the compression ratio, is
at each end of the cylinder head
where there is no stud. The most
common point of gasket failure on an
eleven stud engine which has 11.0:1
plus compression is across the middle
cylinders. If this happens on a
correctly prepared block and cylinder
head, the engine will almost always
have done a considerable amount of
work, and replacement of the cylinder
head gasket the instant the leak is
noticed restores the situation.
Here extra stud hole has been drilled and
tapped.
The cylinder head gasket to use
on any high performance 998cc
engine is the MG Metro Turbo one,
Some of these blocks are sleeved from
the factory. Blocks get sleeved by
factories because it’s cheaper to sleeve
the blocks to make them serviceable
than it is to scrap them and start again.
The usual reason a block is sleeved is
because it has porous bores or has pin
holes on the bore surfaces. When
blocks like this are found they get put
to one side and, when there is a
sufficient number of them, they are
sleeved on a mass-production basis,
which is fine for a normal road going
engine. The sleeving is well done, but
the sleeves are quite thin and over
boring is limited to 0.020in/0.5mm
maximum. Caution! - No sleeved
block should ever be used for a racing
engine, and it’s preferable not to use
them in any high performance application. Thin sleeves crack lengthwise
Unipart Metro Turbo cylinder head gasket.
13
SPEEDPRO SERIES
Standard A+ connecting rod bolts.
Lightened (arrowed areas) connecting rod on left, standard on right.
Lightened and balanced 998 connecting
rod (left). Shot peen the reworked areas
(arrowed).
20
failure with any standard productiontype connecting rod, but with the 998
it is generally a low risk situation. New
connecting rods are available from
Motorsport Parts.
The only things that do need to
be replaced for use above 7500rpm
are the connecting rod bolts. The
standard connecting rod bolts are
excellent but, for use above 7500rpm,
as a safety precaution should be
replaced with high strength
aftermarket bolts such as those made
by ARP for instance.
Caution! - Always fit new
standard connecting rod bolts during a
high performance engine build and, if
you will use very high revs or race, fit
high strength aftermarket bolts. If
standard bolts have to be used in any
high revving application, always fit
new ones in the initial build and then
replace them frequently (every 10
hours of full bore running). Engine use
will have to be logged to keep track of
the hours. A broken connecting rod
bolt means a destroyed engine at
8000rpm. New standard bolts fitted to
a high performance road engine are all
that are required.
CYLINDER BLOCK & INTERNAL COMPONENTS - CHECK & PREP
Main bearing tunnel bores have a surface
like this.
tolerance and the surface finish of the
main bearing tunnel bores is altered.
For high performance engines there
are two advantages achieved by
having the block align-honed: the
surface finish is better and the main
bearing tunnel diameter can be
reduced to the minimum factory size
(which will mean that the bearing shell
inserts will have the maximum
‘bearing crush’ allowable within the
factory specifications).
Main bearing tunnel bores which
have had a bearing spin in them are
seldom on size and almost always
have a series of radial score marks. Do
a visual check to see that there are no
radial score marks and measure the
tunnel diameter using an inside
Telescopic gauge being used to measure
diameter of main bearing tunnel bore.
Gap between cap and block being measured with feeler gauges to ascertain bearing
crush.
micrometer (or a telescopic gauge) to
check that they are on size. The 998cc
engine’s main bearing tunnel bores are
nominally 1.8965in/48.29mm in
diameter.
Caution! - When the bearing shell
inserts are installed in the block there
must be a certain amount of ‘bearing
crush.’ Having the correct amount of
crush is what prevents the bearing
shells from spinning and ruining the
engine. To check crush each main
cap/bearing combination in turn is fully
assembled and one bolt is then
released. The side of the main cap
which has the bolt undone will lift and
it is the distance the cap lifts which is
the effective ‘crush height.’ On the ASeries engine the crush height is
0.004in/1.0mm-0.005in/1.25mm.
Cylinder bores are best dead
parallel, but taper of up to 0.002in/
0.05mm is often accepted as being
within tolerance. However, no engine
produces top power with any
perceptible bore wear: consider
0.002in/0.05mm of wear to be the
absolute limit and even this is far from
ideal. Check that the piston to bore
clearance (checked using a feeler
gauge) is to specification. Pistons are
available from various manufacturers
in 0.010in/0.25mm, 0.020in/0.50mm,
0.030in/0.75mm, 0.040in/1.0mm and
finally 0.060in/1.50mm oversizes.
For high performance applications
you just can’t beat a new set of pistons
Measure the bore with an inside
micrometer and the piston diameter with
an outside micrometer - the difference is
the piston to bore clearance.
25
FLYWHEEL & CLUTCH
Orange and grey clutch covers have strengthening plates.
a 998cc engine. Such a powerful
diaphragm takes a quick toll on the
crankshaft’s thrust washers, which can
lead to early engine failure. Note that it
is actually recommended by the
manufacturer that ‘grey’ covers only
ever be used with Cera-Metallic clutch
plates.
a nominal thickness of 0.290in/7.3mm
(0.015in/0.4mm thicker).
Engines equipped with these
clutch plates do tend to ‘squeal’ a bit
when the clutch is engaged, but who
cares about a bit of noise as long as
the clutch is 100% reliable? For racing
this is definitely the only way to go:
these clutches can be abused as much
as you like and will not normally fail.
There is no point in fitting a CeraMetalic paddle clutch plate without
fitting an uprated clutch cover
assembly. A genuine Unipart Mark II
Mini Cooper S clutch cover assembly
used in conjunction with a CeraMetallic paddle clutch plate is usually
the solution to the clutch problems
often associated with torque of up to
80 foot-pounds. The actual diaphragm
must be dead flat when assembled.
Admittedly, it is not normally
recommended that a Cera-Metallic
clutch plate be used in conjunction
with a ‘dark blue’ clutch cover
assembly; this is because of the
surface glazing of the flywheel and
pressure plate sometimes experienced
with this set-up: a problem which can
cause the clutch to slip.
For use with up to 70 foot pounds
of torque, a new genuine Borg & Beck
‘dark blue’ clutch cover and a Cera-
PADDLE CLUTCH PLATE
Those looking for maximum clutch
reliability should consider a ‘paddle
clutch’ which has Cera-Metallic ‘pucks’
riveted to the actual clutch plate. The
standard clutch plate weighs
550grams, while a ‘paddle clutch’ plate
weighs 700grams. These clutch plates
do not wear in the same manner as
conventional clutch plates, irrespective
of what sort of harsh treatment the
clutch receives. These clutch plates are
basically ‘bullet-proof’ and, as a
consequence, have to be worth the
extra expense. They do wear away, of
course, but very, very slowly.
The standard clutch plate, when
new, has a nominal thickness of
0.275in/7.0mm, while the CeraMetallic lined ‘paddle’ clutch plate has
Cera-Metallic ‘paddle’ type clutch plate.
101
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