Single or dual carb question.....

[ericheath]

My 0.0002 cents. Watched various designs for over ten years now. The one spell where there seemed to be quite a few “successful” converts was after HOTT did his Weber 32/36 on an 1100. Now one “expert” had ridiculed anyone that attempted a 32/36 for being too large. His worked well. He made his own manifold, I think, others began using the VW adapter. Some with the VW adapter had issues until using the 2into1 adapter. Jake2012 also had a successful 32/36 along with a neat hidden alternator modification.

That was the major difference in HOTT’s though, and counterintuitive to what you’d think, he used a two-into-one carb adapter. They were designed to place a two barrel on a manifold designed for a one barrel. He used it in reverse. In the couple years that followed there were a number of people who reported similar successes with different carburetors. Theories are just theories, but most guessed the 2into1 adapter maintained or even sped up the charge as it moved into the lower manifold plenum.

HOTT has a couple successful two- carburetor transforms as well.

Another that I saw a video of in action and looked impressive used the VW adapter and a one barrel, but he used smaller runners from the VW manifold to the elbows of our Goldwings. I think they were only 1” in diameter. I thought that might choke it, but in the video he did a few higher rev accelerations through the gears and it was impressive. Speculation there was small runners helped maintain charge speed.

Whatever you design, I suggest trying to make one that can be adapted easily.

I’m leery of the big plenum without sloping the base towards the runners or welding whatever tubes you use to get right to the bottom. If you do have a place where fuel can pool and have a backfire, it could become more powerful with a puddle of gasoline there. I recall one PVC manifold that blew to bits. No one was hurt, but it could have been bad.

Good luck. Your starting out absolutely perfect: lots of pics.

[83Interstate]

I'm using a larger inner plenum to create somewhat of a "swirl pot" if you will. I think one of the reasons the single carbs tend to lose upper RPM Power is the fuel does not get a chance to mix well enough in a small plenum area. I may be wrong but this will be my first complete manifold I have built other than using a Type 3 Volkswagen manifold and a Ford
Escort carburetor with some rubber hose as runners.

I have always been of the mindset that it is the long intake runners that effect the high rpm power in
the single carb conversions.
Every single carb manifold that I have seen puts the carb farther away from the intake valves than the
stock setup does.

Generally the runners are close to 6 inches each side (as for the 3 single carbs I have previously run) these will be 3 inches when complete. I am building a tried and true steel tube with an x design if this doesn't do what the speed shop says it will. This manifold will also have the ability to be split front cylinders from rear and run a dual carb set up once I figure out the linkage. Hopefully I can prove some skeptics wrong and deliver a great new way to easy tune and have all the power.

[83Interstate]

My 0.0002 cents. Watched various designs for over ten years now. The one spell where there seemed to be quite a few “successful” converts was after HOTT did his Weber 32/36 on an 1100. Now one “expert” had ridiculed anyone that attempted a 32/36 for being too large. His worked well. He made his own manifold, I think, others began using the VW adapter. Some with the VW adapter had issues until using the 2into1 adapter. Jake2012 also had a successful 32/36 along with a neat hidden alternator modification.

That was the major difference in HOTT’s though, and counterintuitive to what you’d think, he used a two-into-one carb adapter. They were designed to place a two barrel on a manifold designed for a one barrel. He used it in reverse. In the couple years that followed there were a number of people who reported similar successes with different carburetors. Theories are just theories, but most guessed the 2into1 adapter maintained or even sped up the charge as it moved into the lower manifold plenum.

HOTT has a couple successful two- carburetor transforms as well.

Another that I saw a video of in action and looked impressive used the VW adapter and a one barrel, but he used smaller runners from the VW manifold to the elbows of our Goldwings. I think they were only 1” in diameter. I thought that might choke it, but in the video he did a few higher rev accelerations through the gears and it was impressive. Speculation there was small runners helped maintain charge speed.

Whatever you design, I suggest trying to make one that can be adapted easily.

I’m leery of the big plenum without sloping the base towards the runners or welding whatever tubes you use to get right to the bottom. If you do have a place where fuel can pool and have a backfire, it could become more powerful with a puddle of gasoline there. I recall one PVC manifold that blew to bits. No one was hurt, but it could have been bad.

Good luck. Your starting out absolutely perfect: lots of pics.

Hey Eric, I appreciate the advice and information. I have a thought already about the pooling fuel. I'm going to crease the bottom of the manifold upward like a jelly bean. Then any pudding will be minimal and once the runners AR all in place I will lose some of the mass of the plenum. What I am creating is called a roost boost. As long as my carb and engine are right then it should in theory charge the plenum and keep it moving so the next charge is already there to head down the runner the instant I twist it. If this doesn't work I will use the mass produced stype till my 2 into 1 manifolds are done. I do very much appreciate all the help I can get.

[83Interstate]

Really don't want to take any chance of having an intake detonate some puddle fuel by way of a simple backfire and blow me and my gonads off the seat.

On that note I ordered a 2nd carb and going to go ahead and build a simple pair of manifolds that will put each carb above the head. Always fun trying to reinvent the wheel lol. Now my only hard part is linkage adjustment and jetting.

Thanks guys for all the replies, help and advice. planning to start my manifolds this afternoon. I'll post pics as it comes together.

[ericheath]

It isn’t likely to have a lot of force as it isn’t compressed. As long as you have a decent filter on your carb, I doubt there’s much chance of being killed from it, minor burns if any. But under way and startled by it, could cause a spill or mishap.

[taunusrainer]

Every single carb manifold that I have seen puts the carb farther away from the intake valves than the
stock setup does.

No other option on a flat 4.

The plenum further up:
A good rule of thumb for making a plenum like this is making each runner's volume the same as one cylinder
and the plenum volume the same as the engine.
Make sure that inside the plenum the runners have flared ends.
Look here

[dontwantapickle]

taunusrainer;
in the above link, notice where the injectors are located.
they are pretty much right on top of the intake valve.

I would think that that particular manifold would suck if you were to try to run it NA
by replacing the throttle body with a carburetor.

first.... that carb would be a long way from the valve, and fuel air mixture doesn't like turning corners.
I would totally expect pooling in the plenum.

but.....I ain't no expert on the topic, so......

[gregforesi]

Stock carbs, just a different look. It runs like a stock 1000 and they use the stock synchronizers and air cutoff valve. I run them about 2 months a year (until I miss the bark and performance of the Webers).

IMG_0263.JPG

[CYBORG]

Still a great looking bike!

[gregforesi]

The build is getting a little long in the tooth. So are we. Keep your chin up Eric.

[ericheath]

Wow, how’d you know I was looking at the weather?

83FFC191-876D-4E59-961F-6436DA8BE12F.jpeg

I have a right to hang my chin for the next week.

I think I need to visit my Dad for a while in St. Pete.

Still taking Brutus fishing?

[ob1quixote]

How well does that set-up run with the uneven intake lengths?

[83Interstate]

Scrapped the whole project. Still doing dual carbs and using a pair of Harley super e carbs but totally gone back to the drawing board.

[Rat]

How well does that set-up run with the uneven intake lengths?

Gets to the local pub OK ...

Gord

[83Interstate]

Stock carbs, just a different look. It runs like a stock 1000 and they use the stock synchronizers and air cutoff valve. I run them about 2 months a year (until I miss the bark and performance of the Webers).

IMG_0263.JPG

This is a beautiful machine.