A friend forwarded me your message to the Britcars
list; I'm a longtime contributor who's taking some time
off to get a little work done instead of writing about M.G.s
all day the way I'd like to. :-) But hey, just this once...
You'd like my MGB engine, I think. I've got a nice
hybrid of '65, '71, and '73 parts. From your standpoint,
what makes it interesting is that I've got an 18V block
with an early head on it, which basically means parts that
you have lying around the garage. I'll let you know what
I did to it and you can see whether it's something you'd
like.
Block: early 18V, from a 1973 MGB parts car, overbored
0.030". The good news about the 18V is that it has the
valve relief pockets ground into the deck. The bad news
is that you have to take a file to a couple places inside
the block to clear the con rods if you use the early style
rods, and they only fit one way round even then (more
later when I cover rods).
My crank is from that same 18V, though that's a mistake;
the early cranks (through 18GH) use a harder alloy. You
may or may not be able to get your crank Tuftrided in New
Zealand; that would be worth it if you plan to run high
RPMs, but if you're planning to go up to 8000 RPM very
often you need to cross-drill the oil passages in the crank
and smooth out the exits so that the oil flows out to the
bearing surfaces more readily. I haven't done that, but
I rarley see 7000 anyway now that I'm using this block
on the street.
Have the block align-bored. Fortunately they do this the
easy way on the B, by shaving the caps and then boring
to size on an exact centre. (Ask me sometime about how
they align-bore a Ford/Lotus motor...)
Use the angled-big-end con rods from the 18GB, I think.
These are the toughest; the big ends are split at a 45 degree
angle to the axis of power, so torque is transmitted against
the sides of the rod bolts instead of the threads.
Don't use the crush-washers to hold the rod bolts in; clean
them with Brakleen and use Permatex/Loctite. Use the
highest temperature Loctite you can find, and torque to
exact settings according to the book. Oh, be sure you use
the hardened steel washers, just don't use the locktabs.
Use the three-compression-ring pistons, also from the
18GB, to go with the angled rods. Keep the stock compression;
8.8:1 is just fine. Compression only gets you 4% per point,
and I will send you a lovely photograph of my chewed-up
piston as an inducement not to go too high on the C.R. :-)
(I had to put in new pistons last May when I lost the #4 to
detonation. On the bright side, I outdragged a BMW M5 in
second gear!) On second thought, if you can get 95-96
octane gas (we get 92, but that's RON/MON, so your
compression may vary), you may be able to go as high
as 10.5:1 or so. Compression, however, is not your friend,
not if you plan to drive the car regularly. Go for the overbore
first, which actually increases your compression just a hair
anyway (bigger holes going into the same size combustion
chambers, right?) And the displacement from 1798cc to
1830cc or whatever the 0.030" oversize works out to makes
a difference, as well as unshrouding the valves so that they
work more effectively as well.
Head: I've got a relatively standard head (on the car, that
is...) I smoothed the last inch or so of all five ports, mainly
just taking away casting flash and roughness. (Actually, I'm
using the '71 head now because it's got the stock C.R., and I
understand I could pick up a few more bhp if I removed
the air injection tubes that come in at the back of the exhaust
valves.) Valves are stock big valves; if you use the 18V's head,
be sure to have dual valve springs installed.
Cam: I *love* my Piper Blueprint 285 cam. Idle sounds just
the tiniest bit lumpy -- it sounds like the paddock at a vintage
event, but it still idles at 1000 RPM. But at 4000 RPM, you'll
know why they call it coming on the cam... Power keeps on
going nicely till about 7000 RPM with a good head; I lose
steam about 6500 with the street head and exhaust.
Intake: Stock SUs, 1.5" HS4s. I don't have the needles right,
which may have contributed to the detonation in the #4, but
even so I get reasonable fuel economy and drivability that's
as good as stock, if you do nothing but crack the throttle and
shift at 2500 RPM while waving at the nice policeman. On
the other hand, if you drop the car a cog or two as you come
up to an open stretch, you can rocket past most people
before they realize you used to be behind them.
Exhaust: Stock manifold and downpipe, ANSA exhaust. I've
read a LOT about the MGB and also the A Series engine, and
about exhaust systems in general, and I don't think an LCB
header would gain me much -- and a lot of the headers on
the market will probably lose me power. The stock B's manifold
is about as good as it gets till you go wild on port size; I could
have used a 2" header on the high-compression head, but with
the street head this runs nicely. Use a good exhaust gasket paste
to seal the doughnuts in the cast iron.
Ignition: Stock Lucas 45D4 ignition with points, using the
advance curve from a stock '67. Use the 45D4, not the 25D4.
Look at the way the pinch-bolt holds the distributor into its
timing position and you'll see why. The 25D4 has a little
ring, like a slice sawn off a pipe; after 30 years of ham-fisted
garagemen wan-- er, yanking on the nut after a tuneup, the
ring snaps. (Again, I'll show you a picture...) When this
happens, at first you simply lose timing every 10 minutes.
Then eventually the distributor will jump out of the block
between turn 2 and turn 3 at Sears Point Raceway and the
car will make a huge BANG convincing you that you've
just grenaded the engine in a most festive manner. The
later distributor has the pinch-plate made of solid metal,
cast integrally with the rest of the distributor body. Even
if you go with an electronic ignition (which my friends
insist I'll love, though I point out that I'll be able to
start my car after the EMP from a nuclear blast when
their electronics have all been fried), use the 45D4 as the
body. If you use points, be sure to set the dwell between
51 and 53 degrees, and use no more than about 35 degrees
of advance. We set up my car with a Gunson Colourtune
and a Fluke electronic dwell/tach, then tested it with the
computer as detailed below.
That's all I can think of offhand. Now, for the specs. A friend
with a Vericom performance computer worked out some
acceleration figures for me when I was running the h.c. head
(about 12:1). The computer says we were cranking out 57 bhp
per 1000 pounds at the rear wheels; this in a car that weighs
2100 pounds but had over 400 pounds of people and gear in it.
I usually figure it at 2500 pounds and call it 140 bhp, which is
about right according to the books. I have always figured that
going back to the 8.8:1 head with its smaller ports has cost me
about 20 bhp, but that's still 28 up from a stock '67, and more
than 50 up from a stock 18V. (How good is it? I had a valve
keeper fail on my #1 cylinder, effectively running the engine
on three cylinders, and I still had more power than the car
had on its original engine!)
It's a fun car to drive, because the power comes on in a
nonlinear rush that gets faster over 4000 RPM. This gives it
a great Jekyll-and-Hyde feel, yet it's not uncontrollable as in
a turbo; if you putter around the shops at 2000 -- 3000 RPM,
the car is as tractable as my '63 Volvo, but if you stomp on
the gas and shift at the redline, the car will pull my '82
280 ZX. And it's significantly faster on any winding road,
where the car's additional grip lets me enter a corner about
10 mph faster than the Datsun, as well as being able to get
on the power sooner.
Oh, right. You'll also want to upgrade the tires at least, if
not also the wheels, if you haven't already done that. I'm
running Yokohama A008RS competition tyres, because I'm
a nutcase; they stick incredibly well in the dry, and I have
got several years' use out of them in spite of what everyone
says (they're a super-sticky compound that is designed to
last about 25 laps of the average racing circuit). Of course,
the B's light weight and good weight distribution means
they wear more evenly than on a FWD hot hatch, but I've
put probably 6000 miles on them and they aren't down to
the wear indicators yet. On the other hand, they are not as
soft as they once were; the heat-cycling reduces their grip
but also lengthens their life. I run them on centre-lock
Minilite replicas, as the chassis I put them in came with
wire wheels; the rims I chose are 14 x 5.5, though I have
since seen a friend's MGB-GT with the 15" versions and
it does look sharp. Still, I've had no rubbing problems and
if anything, the 185-60 size increases acceleration and lowers
the car just over an inch. I worked out the gearing, and
putting the 185-60s on in place of 155s is the same as going
from a 3.9:1 axle to a 4.1:1. You do buzz a bit on the highway,
but that's part of the fun.
This year we get that car painted, but that's another story...
--
Every book is a Power Book.
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