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Carter Side Draft

Bill Blue

Platinum Level Sponsor
One of the better kept carburetor secret is the Carter side draft used on the Nash Healey, Corvettes and Corvairs. They came is various sizes, I decided to use a big one, installing it on the Iron Headed 1725 in the '69 Fast back. I decided the carb designed as a performance upgrade for the the big Harely. was a wipeout. It is fine if your feeding a big aircooled engine that needs a consistent diet of rich fuel, especially off idle up to about 2500 rpm. The carb, while tunable, was strange. The low speed jet had no impact on idle or off-idle mixture. The idle adjustment and progression jets being the main controllers. The idle jets impact on the high teens and up. This meant the 1725 ran rich at low speed. It became clear I would need a carb that had a high speed enrichment circuit. Enter the Carter YH.
Here is my Ebay-sourced unit. Remanufactured and equipped for life in the Fast Back with the Iron Head 1725. Also a shot of the engine and manifolding. I have made stuff to mate the Alpine cables compatible with the Carter rod actuated controls.
Bill
 

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Bill Blue

Platinum Level Sponsor
Here it is,complete with a spiffy new air cleaner assembly. One big oopsey. No vacuum port. Will take it off and install a ported vacuum port.
 

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Bill Blue

Platinum Level Sponsor
Finally able to give it a quickie run, the carb performed beautifully. Just hope I continue to be positively impressed as we become better acquainted.
Bill
 

Bill Blue

Platinum Level Sponsor
Another couple of short runs and still looking good. The Carter seems to fire up easily on each attempt, something I could not say about the CD or motorcycle carbs. They could be very difficult if startups were a week or so apart. Especially the CD. It it did not fire up immediately, I would be looking at a severly drained battery by the time it started. The Carter seems to have some engine flutter at low rpm/light throttle. But it may be a transitional warmup phenom, my trips so far have not been long enough to fully characterize it.

Something I should make clear about my diddling with the carb. I did not remove the factory carb - that was done long, long ago. The carb I removed from the engine is a basic CD 150, identical to the Series V carb. The Fastback was supposed to be fitted with an emissions carb, which I definitely did not remove.
Bill
 

husky drvr

Platinum Level Sponsor
Another couple of short runs and still looking good. The Carter seems to fire up easily on each attempt, something I could not say about the CD or motorcycle carbs. They could be very difficult if startups were a week or so apart. Especially the CD. It it did not fire up immediately, I would be looking at a severly drained battery by the time it started. The Carter seems to have some engine flutter at low rpm/light throttle. But it may be a transitional warmup phenom, my trips so far have not been long enough to fully characterize it.

Bill

Bill,

I was hoping you'd been able to take the coupe to Invasion so you could've given some road usage insights. Oh well. I don't know a thing about Carter carbs so was curious.


Something I should make clear about my diddling with the carb. I did not remove the factory carb - that was done long, long ago. The carb I removed from the engine is a basic CD 150, identical to the Series V carb. The Fastback was supposed to be fitted with an emissions carb, which I definitely did not remove.

As to the 150 CD you removed, are you sure about it not being the OE carb? The Haynes manual lists 150 CDS #3162 to be your OE fitment. The CDS models have a separate enrichment valve for cold starts. which is in operation with the starter bar - I think (stuck piston). Considering one of the Alpine's twin CD's used for the entire engine displacement, it would seem to not be an issue generating enough vacuum behind the deployed starter bar to richen the mixture enough to start.

Just for the fun of it, my carb number isn't listed in the Haynes manual, even though it is a Sunbeam fitment.

I also notice my manifold doesn't have the "gulp valve" that's mounted on your unit. A gulp valve is an emissions device designed to keep a fuel/air supply flowing when the throttle is snapped closed to prevent misfires. I know the ones mounted on the Ford SOHC 2000 engines were problematic, expensive, and bypassed or removed, when replacement was required. You might consider playing with the gulp valve to see if it might be affecting your tuning efforts.

Just a thought,
 

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Bill Blue

Platinum Level Sponsor
Don, I will get a couple of photos up, but right now will explain my conclusion about OE carb fitment. I was told that the OE carb was not a CD150, but a derivitive of the CD 150. In addition, the owners manual contains information about tuning the carb. This info mentions adjustments for things that are not present and have no attachment points. I wanted to take the car to the Invasion but life's unwanted demands and a leaky fuel gauge sender gasket (located in the middle of the tank sidewall) were playing dirty pool with us.

Bill
 

Bill Blue

Platinum Level Sponsor
Don, here 'ya go.
Bill
 

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Bill Blue

Platinum Level Sponsor
Drove about 200 miles yesterday, an Old Car/Old Friends get together. Carb did fine, loads up on shutdown. What's the cure? Big problem is that in order to clear the carb, the accelerator must be opened all the way, shooting even more gas into the carb.

Another head scratcher is the shifter. Often gets very stiff, even in the neutral gate. Still shifts okay, just very stiff. Alternator fan became loose, creating a perfect ringing din. Will look into alt problem today, don't know where to start with the shifter. Yeah, I know, always start in low gear. Also, my fingers started cramping. Too much time spent wrapped around a skinny, vibrating steering wheel. Fifty year old cars and 80 year old fingers are not compatible.
Bill
 

husky drvr

Platinum Level Sponsor
Drove about 200 miles yesterday, an Old Car/Old Friends get together. Carb did fine, loads up on shutdown. What's the cure? Big problem is that in order to clear the carb, the accelerator must be opened all the way, shooting even more gas into the carb.

Another head scratcher is the shifter. Often gets very stiff, even in the neutral gate. Still shifts okay, just very stiff. Alternator fan became loose, creating a perfect ringing din. Will look into alt problem today, don't know where to start with the shifter. Yeah, I know, always start in low gear. Also, my fingers started cramping. Too much time spent wrapped around a skinny, vibrating steering wheel. Fifty year old cars and 80 year old fingers are not compatible.
Bill


Bill,

Sounds like an interesting outing. Hope it was fun as well.

Considering your pics and my lack of knowledge on Carter carbs, I can only venture some generic thoughts. To start, it appears you could use a better thermal break between the carb and manifold. Along with that, a heat shield below the carb might help lessen heat soak as well.

Your pic of the mounted carb seems to have it with a slight upward angle. Wasn't the carb mounted level in the OE application? Short of an angled adapter to mount the carb level, you might try to drop the float level to reduce the tendency for fuel to overrun the bowl.

As to the shifter, I'm not sure. It might be as simple as a lack of lube and a bit of rust on the shifter extension rod to something that's loosened and dragging or binding. Hopefully someone else has a better idea. IIRC, the remote shifter for the coupe is the same as a series Alpine with an all-synchro transmission which would simplify sourcing one, if needed.

Just some random thoughts,
 
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Shannon Boal

Platinum Level Sponsor
Um, 50 years ago, my 1965 Corvair Corsa, with that type of carb used to hot soak rich. I would crank at half throttle for a second or two to start, then fast idle to clear it. I guess maybe isolate the carb from heat....if possible.
 

Shannon Boal

Platinum Level Sponsor
I see that our British group use a check valve in fuel line to Alpines for hot soak prevention. GM used them at the fuel inlet nut filter on every variety of Rochester. The reasoning for it seemed complicated, but it might help.
 

Shannon Boal

Platinum Level Sponsor
Ooh! The corvair used a vapor separator filter near the carb! Fuel in and out 5/16" and a 1/4" line off the top of the filter tank return. The return nipple was restricted, had an internal hole maybe 1/16". So, they knew they had a problem....
 

Shannon Boal

Platinum Level Sponsor
s-l500.jpg
 

Bill Blue

Platinum Level Sponsor
Thanks for all the input. Shannon, it seems to me that in this situation, a check valve is not called for. My problem seems to be heat induced oil over. Fuel that sneaks back to the tank would lessen the amount left to be ejected into the manifold. So the check valve seems to send me off in the wrong direction.
Discovered the problem causing the alternator racket. The nut holding the pulley and fan in place loosened and fell off. The pulley was setting on the shaft at an angle. Woodruff key and seat worn into oblivion. Ordered a new alternator on Rock Auto. Cheaper than a rebuilt and the only way I can get a new pulley and fan.

Bill
 

Shannon Boal

Platinum Level Sponsor
On the fuel thing, some thoughts (my own)....1) check valves in the fuel pump and needle valve in the carburator work fine with liquid fuel. In a "hotsoak", the carb fuel vaporizes and vents into the air horn, (over-fueling the intake), the float valve opens as it is not floating anymore. The fuel line did not boil when it was under fuel pressure, but when the float drops it will boil. The vapors escaping the fuel line would go the way of the rest, into the intake manifold 2) So, if with an internal bowl vent, a check valve in the fuel line near the carb would remove some over-fueling during hot-soak.

Having said all that I agree with you, because the primary problem remains heat boiling the carb. Things that reduce carb heat, and maybe things that cool the fuel, oughta help.
I have had good results wrapping the exhaust and opening the hood. I don't have an electric radiator fan, but if I did, I would try a shut-down-run timer.
 

Bill Blue

Platinum Level Sponsor
Finally! Got the correct vacuum port installed, carb setting at an almost correct angle, valve cover breather piped into the air filter assembly and an insulator under the base of the carb. As a side note, the new alternator performed nicely. Warning light is on when the key is in the "ON" position and off when the engine is running. I'm calling that good enough.

I made the insulator out of a piece of bakelite that is probably older than me. It is 1" thick at the top and narrows down at a 5 degree angle to about 3/4" at the bottom. Two birds with one stone. I installed a Pex 1/2" pipe X 3/4" adapter in the bottom of the air filter housing and ran a 3/4" heater hose to the valve cover outlet. Strange, but it appears the stock configuration did not insure burning of the blowby gases or filtration of air sucked into the valve cover.

Made a short (10 mile) shakedown. All went well. The Carter is very easy to live with. On startup, the Strom and cycle carb wanted to fire a time or two, then die. When the Carter fires, the engine is running. It is very smooth with good response. Prolly not as strong as the cycle carb from idle to about 1500, but otherwise very good. Not stock, but better than the non-stock Strom that was on it.
Bill
 

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