>I have been having problems staying ahead of many Japaneese & German cars
>while climbing the Santa Cruz mountains. They all see to have more power
>than the MGB. I have the B floored & they are passing me {on hwy 17} or
>sitting on my tail {old San Jose road}. Whats a poor girl to do!
>I would like to keep the car smog legal, but also get more HP. I have a spare
>set of 1-3/4 carbs from my TR3. Would that help or hinder if I kept the stock
>exhaust & cam? Where is the power restriction in this engine?
The bigger carbs will hurt your throttle response slightly unless
you do a lot of other things as well. The power restriction in
the B motor is basically the cylinder head -- sorry to say...
Bs are real sensitive to happy SUs, though. It's possible that
yours are either adjusted by the book instead of by the road, or
that they're leaking or worn or just not working right. The problem
with most carb tuning is that you tune at idle, but that's not
where you drive. A smooth idle is nice, but I like being able
to chirp the tires in second. (Of course, the fact that the tires
on my car could double as train wheels makes it easier to break
traction...) Clean them inside and out, too, to make sure that
they're operating correctly and that the dashpot is raising
freely when the throttle opens. And experiment with the right
kind of oil in the dashpots; I've tried 3-in-1, Singer sewing
machine oil, Marvel Mystery oil, and plain old Castrol 20W50 GTX,
and I think I like the Castrol best. After all, it's the right
temperature range for the inside of the engine...
Install clean air filters (or clean the reusable ones you've got),
then try tuning the carbs one flat too rich; dial your vernier
advance mechanism on the side of the distributor three or four
clicks toward advanced, install new plugs and points, and see
how that goes. You could also check the valve clearance while
you're tuning; I don't know of anything on the B that works like
the neat, free power trick on Spridgets (where you adjust the
cold valve lash from .012" up to .015" and get a boot at about
3000 rpm), but valve clearances *can* affect power if they're wrong.
As a set of bounds, try advancing the timing till it pings,
then back off a click; enrich the mixture till it doesn't run
right, then back off half a flat. B motors like 12.5-13:1 air:fuel
ratios for maximum power (this is 5%-6% on a CO meter if you've
got one of those).
That's about the only way to tune a B without either adding or
removing metal, though, which gets expensive. If you decide
to get any more bolt-on stuff, though, here are some suggestions
in approximate order of expense:
- Locate some 1967-or-earlier throttle plates for HS4 carbs;
these don't have the spring-loaded button that keeps the
idle high and the airflow low
- Bosch Platinum plugs provide a touch more power and smoother
ignition, but if your engine is prone to oil fouling, it will
foul the platinums permanently
- Mufflers before headers (on pre-'75 cars, the header is OK
unless you want to change other things)
- Get two K & N air filters and cobble up a low-restriction
housing (the cast aluminum plate looks cool but I have
other things to spend $100 on) out of old filter housings
That's about all the bolt-on you'll want to do to an old, stock
motor. If that still doesn't bring the power up to snuff, then
you need a valve job, possibly a new cam, and probably rings
and a few other things -- call it a rebuild. (Note that I
haven't included things like high-lift rocker arms or Weber
carbs, which would only accelerate any wear already present
in the engine.)
Good luck!
--Scott
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