Before considering performance tuning I think you need to think about what
use you are going to put the car to. Does streetable mean a lot of
traffic/city driving or driving through town to put mileage on open roads?
Is your idea of fast 90mph, 110mph or more (even less)?
You need to decide how much money you can properly afford and cost in brake
and suspension mods (this does not necessarily mean fat wheels and tyres).
You need to think about the relationship between torque and power. Torque
makes acceleration whereas power makes top speed. There comes a time with
the Spridget where it is better spending time working on the aerodynamics to
improve top speed (a spoiler, etc) to get another 3mph than working on the
engine to get another 10bhp that will get another 3mph. The same goes for
acceleration, only it is a question of reducing the weight by 30 pounds
rather than get another 3bhp or increasing the efficiency of the torque
multiplier (also known as the gearbox). Whether to spend the money on a
close ratio gearbox (including special 5 speeds) or struggle to get the
A-series to produce more torque (forced induction/nitrous).
There is no reason you can't run a 286 cam in a 1275 and have a streetable
engine. The key to the cam being streetable lies in other areas and as Ron
recently pointed out using Full Radius rams on a 45 DCOE made a big
difference. The problem is the DCOE is mostly incorrectly calibrated and
simply not developed properly and gets a name for being a race only carb,
which is plain simple rubbish.
Think again about the power you are looking for. Will a fairly stock 1430 be
a better bet than a highly strung 1293? High rpm shortens engine life more
than mostly anything else in performance tuning and a hot cam while pushing
the power up does so at a higher rpm while robbing the bottom end of torque.
Will the extra power of a hot cam really be used that often?
On balance though don't be scared of spending the money to get a hot cam to
work. I have a 1312 with a 286S cam on 1.5 rockers than I can drive round
town all day long at 30 - 35 mph in hot weather and won't miss a beat the
first time I open it up in any gear you like to call except 5th and does
80mph in 3rd and will do100mph still in 3rd if I really want to (I prefer
shifting to 4th). Top speed (so far) is no quicker in 5th than 4th but makes
90mph cruising comfortable.
Do read David Vizard's book on the A'Series cover to cover and if you or
anyone else thinks it could be improved upon by including spec builds - give
the guy a break and write and tell him (via Haynes publishing) - how else
will he know what readers want?
Anything between 80 and 110bhp is realistic and easily achievable, after that
you get a diminishing return for your money.
Daniel1312
In a message dated 24/08/00 16:33:11 GMT Daylight Time, yup1275@pacbell.net
writes:
<<
Hi Brad. I have a 71 also. Choosing to leave it stock for awhile and ignore
the
AEG163 S head ala Viz, 45DCOE, 286 new on the shelf -for now. Trying to just
have
a simple, sweet stocker this time. I've had the full race and semi
before and we'll see just how long it takes for me to break down and DO IT.
Oh
well.
D r e a m M a c h i n e :
Balance it. APT stuff. 286 cam is too hot, especially with 1.5 rockers. Try
276
and stock or offset-bushed rockers for less added stress on the valve
operating
system as a whole. Do Vizard's mods to a good head and use rimflows.
Compression no higher than 10:1, even tho these engines really dig high
compression. 40DCOE or a 45. LCB and a nice steelpack for the audibilities -
or
an RC40 for a sleeper. Alden Yellow and optimized radiator with aux electric
fan. Oil cooler depending on where you live. 5-speed to give the engine a
fair
break.
I wrote a treatise for the Mini web about balancing power demand and
longevity.
You could call it stress management. Be judicious about adding stress.
Analyze
those activities that reduce stress, such as balancing,
porting, better exhaust header and cooling the fluids. Consider those that
are
neutral, like improved ignition systems higher output oil pump, degreeing-in
the
cam. Counter with those that add stress, like high-lift cams and rockers,
high compression, forced induction, and higher-rev power band. Balance is
more
than just what your pistons weigh.
The improved head and rimflows will give you better breathing while not
adding
stress. Gotta leave the guides alone. Okay- polish them, but leave them full
length. This should make up the difference between hot and hotter cam.
Yea!
If the trade-offs are fair to the engine and the power band is relatively
unchanged, you could have a happier, sweeter, considerably more powerful
motor.
Engine Stress Management can also be related to factors that raise or lower
temperature. For everything that adds, do something that reduces. A 10:1 CR
raises heat!
With a close-ratio 5 speed box, the engine will last a lot longer (cast iron
doesn't blush). Damn - that was a good little saying!
Higher efficiency and lower stress are the best goals, tweaking reasonably
for
rational use.
David McCartney
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