Yet another single carb thread :) Dan's 1" runners from plenum to custom head flanges

maan takes some reading (and re-readings) to go over all the stuff you folks have covered in a short period, to start to really understand what you've been (and are) up to,

nothing quite like having access to current and all available info,

i had pretty much lost interest in a SCC single carb conversions cos of the mess of finding easy solid & accurate info,

didn't help that my original cod catchers are humming

what some folks do is have all vital pertinent, current and relevant info in a first post that everyone can contribute to, that is updated on the fly, but by one person, often, the original poster if they have access

@ dan, if you can setup access to editing original posts only (by the original author), i could go ahead with a SCC thread

that's just one way to go about it, you can also go with locked threads that only one or 2 folks can make changes to

[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=99427#p99427:1ov5rw8u said:

82a » Thu Oct 10, 2013 3:20 pm[/url]":1ov5rw8u]
maan takes some reading (and re-readings) to go over all the stuff you folks have covered in a short period, to start to really understand what you've been (and are) up to,

nothing quite like having access to current and all available info,

i had pretty much lost interest in a SCC single carb conversions cos of the mess of finding easy solid & accurate info,

didn't help that my original cod catchers are humming

Click to expand...

I hear ya.
I might not have gone the single route if my oem carbs were working as they should but I got so sick and tired of the spitting back into the carbs I had to do something. It's the way I am.
I'm still wondering what exactly causes that spitting. Noone has stepped up with an answer yet.

Hmmm.. Hey dan, i've rebuilt a lot of carbs and i've never had that problem. Maybe you can give me some insight on what you done to them..or didn't do. What year model carbs were they.

[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=99431#p99431:1px3jhag said:

backyardtrouble » Thu Oct 10, 2013 3:48 pm[/url]":1px3jhag]
Hmmm.. Hey dan, i've rebuilt a lot of carbs and i've never had that problem. Maybe you can give me some insight on what you done to them..or didn't do. What year model carbs were they.

Click to expand...

Would need to do this in a different thread or by PM.

[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=99431#p99431:atkhxqc3 said:

backyardtrouble » Thu Oct 10, 2013 5:48 pm[/url]":atkhxqc3]
Hmmm.. Hey dan, i've rebuilt a lot of carbs and i've never had that problem. Maybe you can give me some insight on what you done to them..or didn't do. What year model carbs were they.

Click to expand...

i'd suggest dan starting another thread on that if interested, and focusing this one on his single carb efforts

idea is just that it makes it much easier for new folks to get up to speed and prevents repetitive simple questions, when threads tend to stay focused,

not to mention that threads should just generally be focused on what an original author is interested in, and getting those results

the title, or subject we have is "yet another single carb thread" focused on the author here, dan and his efforts in that direction

As most know I Have been following these several threads on single carb setups.I don't profess to be an engineer, I don't profess to know more about anything than someone else and now I wana maka BUT. See in my family my dad and his brother in law used to work for Jaguar in the UK they were some of the engineers that worked on the D type. My dad and his bro didn't do the design but actually took metal and made it into the desired form. Now the old man is still engine savey even at 91 and we discuss this quite a lot using skyp.

There is an art in designing inlet manifolds and exhaust manifolds so much so that even my old man has made some pertinent comments. the first was why aren't the input tubes (arms) whatever you want to call them the same length? Exhaust manufacturers go to great lengths to design their systems to pulse down the tubes. This pulsing effect achieves two things a smother exhaust but also a bit of back pressure at the right time to push back into the cylinders unburnt fuel during valve overlap. the scavenging effect of the piston sucking in new fuel/air mixture is helped buy the exhaust port remaining open even if for just a micro second, and allows the un-burnt fuel/air mixture to mix with the new batch. now I know from racing small 1000 rear engined Hilman IMP's (that's when Chrysler owned the company) that the the way to gain more power and hence speed and acceleration is MORE AIR means moor oxygen, the more oxygen the bigger the BANG. The Hilman IMP engine was a 4 cylinder motor bored and stroked from 875 cc to 1100 cc. I used 45 DCOE side draught Webber carbs, effectively 1 Choke per cylinder. I used a short but quite straight manifold maybe 3 inches. at the exit throat of the Webber the size of the manifold was matched to the same size, the entry into the head and consequently into the valve chamber was matched to the inlet valve which had been increased, the throats were polished and the aluminium supporting the valve stem was gas flowed to allow minimal disturbance of the flow. There were no bends other than a splayed out inlet manifold to accommodate the difference between the centres of the carburettors throat and the inlet to the head. Bear in mind that this was quite simple as the engine was in line and not a boxer as ours are.

By using a plenum all the carbs 1,2,3,4,5,6,7 or 8 makes no difference it is the plenum that decides the amount of fuel to be given per cylinder and air as the WHOLE of the plenum is used. As air is drawn for outside (via the Air filter) the plenum will dictate the volume of air and consequently fuel that is atomised in the mixture. except in Fuel Injection.

at any one time only one cylinder will be making it's grab on the available air/fuel in the plenum. However, there are some other factors involved 1) being throat opening and the quantity of air passing through the throttle, When air passes through a tube it is restricted, so to ensure that the right amount of fuel is delivers to the right spot we need to make a vacuum in just the right spot to help suck through the right amount of fuel. Two things happen here 1) the area of the choke where the fuel mixture jet is placed the air is constricted so to enable the air to successfully pass the restriction it must move faster, in moving faster there becomes a partial vacuum caused by the increased speed of the air, quite often one will see a small hump where the needle jet passes through the venturi this causes a very slight but definite reduction in pressure which in turn is able to suck more fuel through the jet. as it passes the venturi the chamber expands quite rapidly, this rapid expansion has two effects on the mixture, the pressure drops which causes the gas to go cold so very slightly which causes the fuel to vaporise better before it hits the inlet manifold on it rush to the cylinder that is about to start it's inlet stroke. We all know that both exhaust and inlet valves have an overlap the exhaust encourages new fuel/air mixture into the cylinders.

I know this is a bit long winded but please bear with me. So at this point the piston starts it's return up the cylinder to compress the mixture where the required power stroke will take place.
On an engine like the Hillman IMP we didn't have a plenum, each cylinder had its own choke, one choke one cylinder. What we are doing here is utilising one big volume full of air fuel mixture that is mathematically being allowed to move via a low pressure being created in the cylinder this in turn will influence the direction taken by the fuel/air mixture. Now come the part that the lines as you like to call them are in fact failing (please note this is my opinion and view on these discussions) surly to ensure equal charge of fuel/air into each cylinder then the mixture must travel the same distance from the plenum to the cylinder head via the valve. By having two straight tubes (looking from the back of the bike nr1 front left, nr2 rear left nr3 front right and nr4 rear right) #1 and #3 are a) straight from plenum to head, with a distance of X" or Y mm of travel. The other two are longer by virtue that they have to bend to reach the cylinders from the plenum ERGO they are different length whereas the OEM pipes are equidistant.

Surly this 10mm or 1/2" or 3/4" whatever has a bad timing affect on the fuel reaching it's destination IN TIME. You cannot deny that all the tubes in these discussions are in fact different lengths this will result in incorrect fuel delivery times. it may be almost minimal but it will have a big affect on the firing and power produced. You will be effectively be running on 3 and a 1/2 cylinders without noticing.

Engine manufacturers go to a lot of trouble to attain equality as timing is the key word. So I am wondering weather the current consensus is maybe overlooking a simple but very important point. That point being that the inlet and distance travelled by the fuel/air mixture should be equal and matched over all 4 cylinders?

I have no doubt equal intake tubes lengths would be the ideal.
This is one of the reasons I think using the stock rack with a carb on top deserves more attention.

Or vw manifold with a frame modification??

Here is my first Venturi

You can see the reduction in ID open widest at the vw manifold and smallest near the head

From VW plenum Outlet, to OEM manifold.
1.300 ID, 3/4" long, 1.170" ID x 2.00" Long, 1.050" ID x 1.00" Long. then opening back up to 1.300" again

This is the 1.050" Last part of the Venturi before it enters the 90 degree turn down word

You are seeing down into the Venturi, looking down from the VW manifold end is 1.300" x 3/4" long then 1.170" ID x 2.0" long, then 1.050" ID x 1.0" Long

You are seeing down into the Venturi, looking down from the VW manifold end is 1.300" x 3/4" long then 1.170" ID x 2.0" long, then 1.050" ID x 1.0" Long

hmmmmm my chokes are somewhat different ...and the stock rack plenum is not forgotten by me it going to :builder: :mrgreen:

i don't think the stock plenum or frame hacking will catch on

bolt on simple simple simple, known to work well, easy and cheap is what i'm after

once i have that, i'll start looking at other stuff

[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=99973#p99973:uk034poc said:

82a » Mon Oct 14, 2013 12:05 pm[/url]":uk034poc]
i don't think the stock plenum or frame hacking will catch on

bolt on simple simple simple, known to work well, easy and cheap is what i'm after

once i have that, i'll start looking at other stuff

Click to expand...

+1 :yes:

i'm not clear as to what's goin on in those runners? can you take them/it (plastic parts?) out and snap a pix?

[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=99910#p99910:20f2k06w said:

westgl » Sun Oct 13, 2013 9:16 pm[/url]":20f2k06w]
Here is my first Venturi

You can see the reduction in ID open widest at the vw manifold and smallest near the head

From VW plenum Outlet, to OEM manifold.
1.300 ID, 3/4" long, 1.170" ID x 2.00" Long, 1.050" ID x 1.00" Long. then opening back up to 1.300" again

This is the 1.050" Last part of the Venturi before it enters the 90 degree turn down word

P1020183

• westgl
• Oct 13, 2013

1.050" ID Smallest opening of the Venturi, this is the last 1" of the venturi

You are seeing down into the Venturi, looking down from the VW manifold end is 1.300" x 3/4" long then 1.170" ID x 2.0" long, then 1.050" ID x 1.0" Long

P1020184

• westgl
• Oct 13, 2013

A look inside the completed Venturi

You are seeing 1.300" x 3/4" long then 1.170" ID x 2.0"...

You are seeing down into the Venturi, looking down from the VW manifold end is 1.300" x 3/4" long then 1.170" ID x 2.0" long, then 1.050" ID x 1.0" Long

P1020185

• westgl
• Oct 13, 2013

A look inside the completed Venturi

You are seeing 1.300" x 3/4" long then 1.170" ID x 2.0"...

Click to expand...

It looks like my thread has been hijacked, oh well it's all good stuff.
Keep it coming guys.
Like the mikuni head clamps in the other thread, it's amazing what comes to the table when we can freely brainstorm and present them!

[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=100095#p100095:of5fgoxj said:

dan filipi » Tue Oct 15, 2013 11:08 am[/url]"f5fgoxj]
It looks like my thread has been hijacked, oh well it's all good stuff

Click to expand...

"Right turn, Clyde..." :smilie_happy:

[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=100095#p100095:8qszy8tb said:

dan filipi » Tue Oct 15, 2013 11:08 am[/url]":8qszy8tb]
It looks like my thread has been hijacked, oh well it's all good stuff.
Keep it coming guys.
Like the mikuni head clamps in the other thread, it's amazing what comes to the table when we can freely brainstorm and present them!

Click to expand...

nah, may be sidetracked a bit :whistling: :hihihi:

heh, you started this (Yet another single carb thread ) party, you can jump right back in anytime

plus, easy enuff to sum up stuff in a fresh thread

Ok picking up where I left off.......

I'm continuing forward to use the 1" runners because I think 1" is big enough and curiousity has got the best of me how they will perform with smooth flows and air tight.

Starting with adapting the 1" pipe to the orange VW rubber couplings, I'm after a smooth transition from the plenum to the intake ports at the heads.
This first brazing is a trial to be sure I can mate the parts by brazing and get the fitment I'm after:
























More filler and grind smooth.

After more filler braze and smoothing with a dremel sander wheel.
The finish is smooth as glass.

Very nicely done. I can't wait for the finished product and ride report.