~ This time around I'm getting the block bored out to fit the
~ "big bore" 77mm pistons whic will come with a balance set of
~ rods. I'll be trading the Faspec 3/4 cam for a somewhat milder
~ version. I'm also replacing the tappets (I recground them the
~ first time through), and oil pump, and I'm thinking about a
~ Mallory dual point distributor to replace the one I recon-
~ ditioned.
Am I just confused, or are there 87mm piston/liner kits for the big TR?
~ The Green Man has been a real
~ stomper of a car for me, but it could be a bit more tractable
~ for just driving about.
The reason I ask is that it's generally true, particularly for a
street-driven car, that there ain't no substitute for cubic inches.
You not only get additional displacement, but on typical English
long-stroke/narrow-bore motors you significantly unshroud the valves
as well, leading to better breathing at all RPM levels, as well as
often improved cooling and fuel economy (assuming you can restrain
the right foot, described by many racers as the body's second
stupidest organ).
Do NOT get too aggressive with compression; you only get about 4%
per point of CR bump, and it's just too depressing to pick chunks
of aluminum out of your exhaust manifold. Been there, done that.
If Piper make a version of their MGB "Blueprint 285" cam for the
big TR, I recommend it highly. It's tractable under 3500 RPM (my
current self-imposed redline till the rings seat; just passed 150
miles on them on the way to work!), but *really* sings over 4000.
For the street, a good distributor is important, as you will be
spending so much time inside the advance curve; typically, most
distributors max out on advance within a few hundred RPM of 3K.
On track, you don't care about that as the only time you're under
3K is behind the pace car or in the pits, but when you've got a
cop on one side of you and a diesel Mercedes in front of you,
tractability is nice. Aldon have a great reputation for building
nice performance distributors. I used a stock advance curve for a
1965-67 MGB in mine, and I'm very happy with it; it'll probably
work even better once I install the vacuum line.
Something that you might consider is going with high-ratio rocker
arms. These can put extra wear on the valve stems unless you also
go with roller-rockers (think about it -- you're describing a larger
base circle than the stock rockers, hence there's more lateral load).
It's not cheap -- good roller-rockers can run you $600 -- but it
lets you get more lift from a cam with modest characteristics, one
way of keeping reasonable idle with higher top-end performance.
Most of all, don't neglect the details. Even if you don't go with
a full port job, detail the interface between the manifolds and the
head. People used to match the ports, laboriously scribing and
rechecking to get the ports and the manifolds lined up perfectly.
Not necessary: what turns out to work even better, especially on
the street, is to have a step of a millimeter or so between the
two components, with the larger chamber downstream of the step.
This helps avoid reverse-flow pulses while actually improving
forward flow as well; I can vouch for its effectiveness as well
as its simplicity, having done it with great results on my MGB's
cylinder head. And don't bother with a mirror-finish on the
exhaust ports, either; they'll become sooted up within minutes
and you'll lose any effect of the high shine. On the M.G., at
any rate, I noticed a distinct improvement just by reworking the
outer 1" or so of all the ports, as well as by reshaping the
stock exhaust manifold. You can also consult your machine shop
to see about multi-angle valve jobs, and be sure they use good,
high-quality valve springs; yes, just replace them all, particularly
if you're going with a hotter-than-stock camshaft. It's worth it
in high-end smoothness.
Anything else? Have all your internal engine components balanced.
This means end-for-end balancing of the rods, the crank, and the
flywheel. If you can have a good shop take some weight off the
flywheel, you'll feel it in sharper throttle response as the
engine has less mass to accelerate before the power even gets
to the tranny's input shaft. Make sure the shop knows to do
little things like radiusing the edges of the crank journals to
avoid stress risers; if you're going to see high-RPM operation,
you might also want to talk to them about chamfering the output
holes on the crank to improve oil flow. This (I've only seen it
in books; for some reason I didn't have them do it to my crank)
consists of smoothing out the trailing edge of the oil hole in
the crank journals, so that oil flows out more easily and keeps
the bearings lubricated a little better. Neat trick. If you
*really* want to have some fun, have them knife-edge the
crank throws to reduce aerodynamic drag in the crankcase. On
my next motor I'll do that... :-)
When you put it all back together, Permatex 3H is the recommended
gasket sealer for the pan, the front and rear gaskets, and any other
potential oil leaks. It's great stuff, but it will effectively glue
your engine components together, so get it done right the first time.
Also, though it has nothing to do with actual performance, take the
time to clean thoroughly and then paint any components you like.
It's worth it to see a gleaming, freshly painted engine drop back
into the bay as you finish your work.
Best of all... there is nothing to compare with the feeling of
motoring down a leafy lane powered by an engine you constructed
with your hands, your head, and your heart, an engine whose every
power pulse happens because of your own effort and study. That's
what makes these cars so special, and what makes the people who
own them such wonderful folks. Do the rebuild over winter, but
don't finish it *too* far before spring or you'll go mad waiting
for the first buds and snow-free lanes...
--Scott Fisher
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