Difference between 1bbl and 2bbl on 225 slant 6 3.7L
Terence Yomogatsu
Plymouth Volare wagon. It have 1bbl carburator. Mechanic say 2bbl have
more power. engine big 3.7 liters so i think that 1 bbl good for big
engine. second, car have rust on fender. can maco or earl shibe fix it for
good dollar amount? i like to cruise ventora bullevard to pick lady up
after paint.
Cloaked
call "progressive" - especially in the mid to late 70's. That is, they
act like 1/2 of a 4 barrel. So they will run on one barrel until you
punch it. Then the other side of the carb will lick in. I believe most
of these engine/carb combos had EGR.
This is in contrast to the 60's 2 barrels commonly found on V8s like
my old Buick. Those carbs ran both barrels all the time. These babies
were long before EGR. The older 2 barrels were better than a 4 barrel
for someone who is a lead foot. Kicking in the other side of a 4
barrel carb is a major fuel drain!
I used to have an old Nova with a 250 CID engine - about 4.3 litre if
I am not mistaken. It had an old "B" style float in it, and was a 1
barrel. It ran just fine! Lots of power - Just not as much as larger
engines with 2 and 4 barrel carbs on them.
hth
Daniel J. Stern
> If I recall, and this is a generality, many 2 barrel carbs are what I
> call "progressive" - especially in the mid to late 70's. That is, they
> act like 1/2 of a 4 barrel. So they will run on one barrel until you
> punch it. Then the other side of the carb will lick in. I believe most
> of these engine/carb combos had EGR.
1) There were no progressive 2bbls on any factory slant-6, anywhere in the
world.
2) There were no non-EGR 2bbl installations on any factory slant-6
passenger car first sold in North America.
> This is in contrast to the 60's 2 barrels commonly found on V8s like
> my old Buick. Those carbs ran both barrels all the time.
This is the type that was used on the '76-'80 North American
Chrysler-product slant-6 vehicles with the 2bbl setup.
> These babies
> were long before EGR.
EGR has nothing to do with what kind of carburetor (or fuel injection, for
that matter) is fitted.
DS
Student-Mechanic
______________________________
Sort of a misconception. Put 3 deuces on a Chevy Six and it will not use more
fuel than a single Rochester on a lb./hp hour basis. The idea of "a lead
foot" is to get the maximum full throttle performance. Let us say for the
sake of argument (not reality) that with a single barrel, you could get 110
hp. And with six barrels, you could get 220 hp. Naturally, you would expect
(and NOT CRITICIZE) to burn twice as much fuel during the extra output. This
is physics and nothing to do with the number of barrels. The mixture to be
combustible at maximum power production has to be within a narrow range, just
rich of stoichiometric. Maybe 10 or 12 to one.
With the throttle backed off, the fuel consumption will be proportionally
less. In the case of multiple progressive carbs like three twos, the reason
for the progression was to maintain a minimum flow through the barrels. At
idle and part throttle, there isn't enuf air flow to feed fuel and fuel
starvation, not enrichment would occur with overcarburation. That is why the
extra four barrels kick in at 75% or more throttle depression.
The main reason for big V-8s being sold with two barrel carburetors as the
standard engine was cost, not to keep fuel consumption reasonable. Again, the
two barrel models only gave the superficial appearance of being more fuel
economical, but only because their horsepower was strangled by
undercarburetion. Fuel economy could have been even more "improved" by
limiting the butterfly to 50% maximum!! But then, you would have had trouble
outrunning your exhaust gases.
It is always more fuel efficient to extract more horsepower from ligher,
smaller displacement engines and durability, with all things being equal, is
inversely related to h.p./c.i. This axiom is amply illustrated by the 2.2
liter turbo, which is a marvel in that it is impressively powerful, but its
durability is seriously in question.
Cloaked
What I was getting at relates more to the habbits of drivers than
physics. I have noticed that a lot of people tend to race between the
red lights in traffic! ;)
Of course the other side of the 4 barrel has to open up in order to
get the performance. I have no problem with that. However, there are
circumstances where you want a little more acceleration, not a lot. Or
cases where drivers punch the accelerator perhaps heavier than they
need to. When you have a 4 barrel, these situations can open the other
side up - and when it does, it sucks a LOT of extra fuel.
Looking at the response curve of a 4 barrel, you would find a limit,
after which point the fuel flow jumps up by a step, then the curve
would continue in a linear fashion until the absolute limit of the
carb was reached. Compare this with the 2 barrel who response curve is
"linear" without the huge step attributed to the extra barrels kicking
in.
When operating in the range close to where the "step" of the 4 barrel
would be, the driver can get more power without jumping up over the
step. This prevents excessive consumption of fuel. If a driver punches
the accelerator, then the increase in fuel is directly relational to
the amount the accelerator is depressed - unlike with the 4 barrel.
For an average driver wanting average performance, then the 2 barrel
was the way to go. For a Hot-Rodder who wanted pure performance and
did not give a flying fig about gas milage, then the 4 barrel was the
way to go. And for a disciplined driver who wanted the best possible
gas mileage, who could resist the temptation of kicking in the other
side of the 4 barrel, then the 4 barrel offered better economy - but
ONLY IF the second side of the carb was not engauged.
My brother had a 350 - 4barrrel. He used to document his gas milage.
As I recall, his milage would drop between 5 to 10 MPG if he kept
lead-footing it and kicking in the other side of the 4 barrel. Seems
to me that after the price of gas started to rise he stopped
lead-footing it. :))))
As always YMMV
On Tue, 04 Mar 2003 21:26:05 GMT, "Student-Mechanic" <sm7...@msn.com>
wrote: