> Are there any books out there similar to David Vizard's "Tuning the A
>Series Engines" except oriented toward the B series engine?
Lindsay Porter's BMC B-Series Engine Data is about the best bet.
Tip for the week: don't bother with the "Improve & Modify your MGB"
book. I finally got the chance to look through it and it's pretty
much a collection of information available elsewhere in better form.
> If I have enough money left over, I'm contemplating upgrading the
>header/exaust manifold. Again, any suggestions?
The B scarcely needs it, because the pre-75 header is actually fairly
good. If you do upgrade to a header, get the factory LCB manifold.
Many aftermarket headers don't flow as well as the stock piece, so
be sure you're getting some improvement for your money and time.
You'd be better off on a street B going with a low-restriction muffler
and exhaust system.
Power in Bs comes from:
- compression. The B cylinder head can take up to about 10:1
if you're willing to run on 92-octane or better and get the
timing dialed in just right.
- unshrouding the valves; increasing displacement is one way to
do this, as is cutting valve pockets in the deck of the block.
Best to be SURE what you're doing to be positive you've got
room for the gasket.
- porting modifications. Smooth them as much as possible,
change the shape slightly, and keep velocity high for the street
(that means small but efficient ports).
- valves. Rimflo valves (not cheap) are worth a couple of hp
because they make it difficult to flow backwards; they have
turbulence-inducing grooves ground into the face of the valves
at the appropriate point to reduce backwards flow across the
valve. This is a big problem with A and B series engines
due to the siamesing of intake and #2-#3 exhaust ports.
- cam. Lift, timing, and overall duration vary so much that you
should get specifications for any cam you want to buy, or talk
with a really good speed shop. There are lots of cams out there
for the MGB, but as with the header, not all of them will work
any better as an all-around compromise camshaft than the stock
one.
- carbs. Buy a pair of '67-or-earlier throttle plates and
install them. Plug the gulp valve and the holes from the
cam cover breather. Install good air filters (K & N) and
be sure you leave the factory aluminum plates in place; they
shape the incoming air, which has a huge effect on SUs. Note
also that for maximum power, the carbs need to be a little
rich; this, however, drops your fuel economy and can load up
the plugs. (In extreme cases, rich mixtures can also wash
the oil off the cylinder walls and increase engine wear.)
- distributor/ignition. Make sure that once all this air and
fuel gets into the motor, it will go boom in the right sequence.
I recently upgraded to a Lucas Super (not even a Sport) coil
from the Diamond Cheap-O-Matic coil; I also put in new plugs
and wires at the same time, so it's hard to say what made the
most difference but there's more power than there used to be
and starting is much easier on our cold-for-California mornings.
Everything here, according to the books, will net you about 130 bhp.
That's compared to 92 on your stock '69 B; given your worn-out cam,
I don't know what you've got now. But I can assure you that a 40-
percent increase in power will get your attention. If you don't
go wild on compression, lift, or valve size, you should also have a
strong, reliable street motor for many years.
--Scott
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