Recently, I have received numerous calls
on the same subject, and so it’s time to respond. In this
article I would like to set the record straight on the
subject of "Big Bore" Carburetors used for our
Zenoah and other similar gasoline model engines. Once
again, let’s step into our ENFORCER time machine. This
time the year is 1985.
The first two years of Enforcer consisted
of building stock "string trimmer" engine powered
boats. Our new customer base was thrilled to own and operate
these types of models, but I and a couple close customers
(friends) wanted to make them faster.
We were all involved in competition Nitro
boating, and were part of (at the time) the largest model
boat club in the USA. The Broward Model Boat Club had
well over 100 members. There was a short time in (1985-1986)
when we set up our gas engines up to run on 20% nitro,
and boy did that wake them up! Unfortunately, the plant
that refined the majority of Nitro "blew-up"
and NHRA purchased most of the inventory around the US.
This left the hobby industry in short supply and man did
the price per gallon sky rocket. I remember having to
sell 20% for over $30.00 per gallon that year. These big
gas engines would consume nitro at a rate 2 to 1 over
gasoline. We were lucky to get 20 minutes out of a 24
ounce tank of fuel.
While we ran Nitro, we made leaps and bounds
on carburetor technology which in turn gave us the knowledge
to do the same for gasoline, so we started to internally
modify then the Mitsubishi T-110 23cc engine to perform
better with gasoline. To do this, I had to find a good
basis for carburetion. We determined that the .430-.450
intake bore was very adequate for use with gasoline, and
out of over 50 Walbro carburetors we tested, the WA167
seemed to be the best all around carb. At that time, I
had a customer in Walbro who helped with the testing,
he was a new gas modeler as well, so this worked out great
for the both of us.
I thought it would be great to market this
carburetor as an aftermarket product, (actually I believe
it was our first) and I needed a cool name for it. At
the time, I was involved with racing VW-engine-powered
dirt “midget” cars and was in the process of building
a new engine for my race car.
I had just received a new set of 88 mm jugs and pistons,
and in the VW industry, these were known as "Big
Bore Kits". As I looked at the WA167- with the larger
intake bore, the name came to me easily... "Big Bore
Carburetor." Today, many years later, this name has
become generic almost like KLEENEX. This is also the root
of many people’s confusion.
We began selling them, and over the next
couple of year- they became a big hit. The year 1989 brought
our biggest event- we hit 39.8 MPH on gasoline! Now you
are all probably laughing about this knowing what you
do today, but I can assure you I was one of the guys who
said that gas engines would never be able to break 40mph
in the early days. Good thing I wasn't involved in the
Space Program...
I was so close! I needed a better and bigger
carburetor! Here's where the story gets good.
A friend of mine (another customer) was into large-scale
flying and had a twin-cylinder 50cc Italian gas engine.
It had a European carburetor and needed a rebuild kit.
We couldn't find one, so I gave him my box (collection)
of Walbro carbs, and invited him to try and see if one
of them would work. It being it an aircraft, I wanted
no involvement with even recommending one much less bolting
one on his engine. The wrong carb on a $5000.00 model
airplane isn't easily retrieved with a Tennis ball and
reel!
I don't think it was a week later that he
came into the story raving about how great his engine
was running with one of the carbs I gave him. I met him
out at the airfield that weekend. He was right. The engine
ran smooth at all RPM's, and he said it had more power
than ever.
The carb in question was none other than
the Walbro WT257, go figure. I remember looking at the
boar a couple of years earlier and saying, "This
one's a bit too large" and put it back in the box.
I replaced the popular 167 with the new WT 257 "Big
Bore Carb" and it became another great seller, specifically
for racing. This carb was the best to date. I was able
to get more aggressive (now using the Homelite engines)
with the intake timing, and that same year, we broke the
40 MPH barrier for the first time in gas model boating
using a modified 25cc Homelite engine in our Team Enforcer
Pro. I still have the boat.
It was 1990 and competition (LSG) Large
Scale Gas boating was beginning to take off in the Southeast,
and would soon spread all over the country. The starting
point was The Broward Model Boat Club, my Alma-Ata and
Miami soon became involved, then Palm Beach, Georgia,
North Carolina, Las Vegas, and on and on. This prompted
even more of our race program and Enforcer boats were
in competition and winning all over the country.
I still had one problem to overcome- the
lag in transition from low speed to high. This amplified
when I took the intake timing further down, but the timing
also benefited at top end. I called my buddy (engineer)
at Walbro and explained the condition I was facing. He
recommended that I try the same carburetor body as the
WT257 but use an injector/accelerator pump (spray mister)
in the venturi. This carb was being made for a company
manufacturing a commercial "back pack blower",
they needed a quicker acceleration.
He assured me that this carb was exactly
the same as a WT257 only with the pump feature. We tested
it, and found it eliminated the low to high speed lagging.
I made a deal with Walbro to purchase this carb exclusively
for the hobby market. The CA5003 was born. So in 1991
the CA5003 "Big Bore" Carburetor replaced the
WT257. This became to industry’s number one choice and
was used in over 6,000 modified Enforcer Homelite 25-30cc
engines.
We moved the company to Lake Placid Florida
in 1993, and I made the tough decision to leave gas model
boat racing to apply all of our company's efforts into
what was becoming the fastest-growing segment of model
boating. I referred to this new customer base as the Sport
Performance gas model boater. I knew I couldn't devote
the time and attention that both segments of the market
deserved. We did, however, keep in touch and continued
to support our racing customers on a non-factory level.
On a side note, in October 1997 WHH was involved with
setting a new IMPBA world speed record for LS HYDRO at
56.991, with a wooden 60's style Shovel Nose Hydro designed,
built, and ran by one of my good customers Glenn Wiecek
of IL. This was powered by our "over-the-counter"
Enforcer 30cc Pro-Modified Homelite, with a Pro-Wet tuned
pipe system, and our CA5003 "Big Bore" Carburetor.
I really did enjoy working with guys like Glenn, and appreciate
what he and others did to help us grow in knowledge. As
a matter of fact, Glenn's boat prompted me to design the
Enforcer Stingray.
Recently, there has been a resurrection
of the WT257 and most people are replacing the WT644 (carburetor
supplied) with the Zenoah G260 engine. You need to know
that these two carbs are the same. As a matter of fact
our CA5003 is based on the same throttle body as well.
The only difference between them is that the 644 has a
primer bulb and a choke, the 257 has no primer bulb or
choke, and our CA5003 is the 257 with the accelerator
pump. I build modified Zenoahs and have tested all three
many times.
The difference, on the top-end, between
the WT257and WT644 is less than 50 RPM's under load. For
the competition racer every little bit helps, and I too,
would use a carburetor without the air restriction from
the choke plate, but as a Sport performance weekend warrior,
in my opinion the choke and primer bulb are a real nice
feature. They definitely make starting your engine easier.
Now between the WT257 and our CA5003, our
carburetor wins hands down. You will notice a much smoother
transition throughout the throttle range and both needle
valves can be adjusted for good low-end and high-speed
performance; this is due to the accelerator pump.
When comparing these three well-known carburetors,
just look at the specifications below. The throttle bodies
and metering are all the same, and there is very little
performance difference between them when used by the average
model boater.
I was on one site where it say's that the
WT-257 has a bigger bore than the WT644, but their specifications
show them the exact size?
At WHH you get the facts, but with some
other companies, like John BonJovi said, "They’re
all the same only the names have changed"
Before I go I would like to solve one of
the biggest carburetor mysteries, the number that is cast
into the venturi of a Walbro carburetor. It is very simple
and specific for Walbro, actually no real science but
a little bit of 5th grade math. Are you ready?
The number represents 64th's in fraction,
so for instance, if the number on the venturi is 32 the
venturi opening is- 32/64"
Like I always say, Education is the best
advertising.
Thanks and have a good and safe model boating
season,
Tony Castronovo
President, Warehouse Hobbies Inc. / Enforcer Mfg. Co.
CARB SPECIFICATIONS:
| WT-644 |
SOLD WITH ZENOAH G260PUM |
| VENTURI BORE |
12.7MM / 0.500" |
| MAIN BORE |
15.8MM / 0.620" BEST FOR SPORT/PERFORMANCE
USE |
| PRIMER BULB |
YES |
| CHOKE |
YES |
| MOUNTING |
1.25" / 31.75MM (ON CENTER) |
| WT-257 |
(AFTER-MARKET) |
| VENTURI BORE |
12.7MM / 0.500" |
| MAIN BORE |
15.8MM / 0.620" PREDECESSOR TO THE CA5003
ENFORCER CARBURETOR |
| PRIMER BULB |
NO |
| CHOKE |
NO |
| MOUNTING |
1.25" / 31.75MM |
| ENFORCER CA5003 |
(AFTER-MARKET) |
| VENTURI BORE |
12.7MM / 0.500" |
| MAIN BORE |
15.8MM / 0.620" BEST FOR COMPETITION USE |
| PRIMER BULB |
NO |
| CHOKE |
NO |
| ACCELERATOR |
YES |
| MOUNTING |
1.25" / 31.75MM |
