Runner length

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Having spent a good bit of time reading everything I can find here about the single carb set up about the only thing I'm having trouble wrapping my mind around is the need to have all the runners exactly the same length. Taken to an extreme, the intake runners on my Chrysler slant 6 were a study in "how different can we make them" and except for cold weather starting (below -35F forget it) they worked fine. Has anyone actually played with this and found a real difference?
 
Ideally they should be the same but it isn't critical. If they are the same there is a magic point in rpm where you have a boost power. All things come together at that point to create the perfect fuel charge condensed tightly and rushing toward the intake valve just as it begins to open. The rest of the time the charge is a little before or after the valve opening in the timing of the fuel charge bounce. The slant six was a hugely dependable motor but there was never any sweet spot where it had gobs of power.
 
[url=https://classicgoldwings.com/forum/viewtopic.php?p=138658#p138658:3t42xjol said:
slabghost » Sat Jan 03, 2015 8:58 pm[/url]":3t42xjol]
Ideally they should be the same but it isn't critical. If they are the same there is a magic point in rpm where you have a boost power. All things come together at that point to create the perfect fuel charge condensed tightly and rushing toward the intake valve just as it begins to open. The rest of the time the charge is a little before or after the valve opening in the timing of the fuel charge bounce. The slant six was a hugely dependable motor but there was never any sweet spot where it had gobs of power.

Thanks. That puts it in perspective relative to the complete design used. And actually I did have one 64 Signet hard top I wish I still had. Came with a factory four barrel and different exhaust header. Felt more like a 318. LOL
 
My runners are over an inch difference in length left to right banks.
I am getting some primary chain noise, or internal engine noise from this 1200. Was the same on the 1100 with this single setup. I can't say one way or the other if this difference is causing the engine noise because both engines I've had this build on are of unknown mileage.
The noise is similar to carbs out of sync and the 1100 had the same noises with synced stock carbs.
 
Interesting Dan. So what I'm getting out of this is that equal length might be a goal to shoot for but if a little off it's ok.

Had an issue with the old Guzzi yesterday. Started up and would only run on one cylinder. Turned out to be a bad plug but while trouble shooting the thought of a possible single carb jumped into my head. :idea: The battery is already moved so there is lots of space............ :nea:
 
I was able to get the runners on my '82 single carb build pretty close to the same length...within a millimeter or 2. With free swiveling elbows at the heads and fuel hose I am able to loosen the hose clamps off and move the plenum around to try and get equal runner length.
The bike runs pretty good but I don't know if the equal runner length makes much of a difference. I still get some primary chain rattle on take-off sometimes.

Brian
 
[url=https://classicgoldwings.com/forum/viewtopic.php?p=138650#p138650:1pnhjnqy said:
sparrowhawkdesign » Sat Jan 03, 2015 9:39 pm[/url]":1pnhjnqy]
Having spent a good bit of time reading everything I can find here about the single carb set up about the only thing I'm having trouble wrapping my mind around is the need to have all the runners exactly the same length. Taken to an extreme, the intake runners on my Chrysler slant 6 were a study in "how different can we make them" and except for cold weather starting (below -35F forget it) they worked fine. Has anyone actually played with this and found a real difference?

I noticed when i was servicing inline 4s, and a few inline 6 engines, that was made in the 50s, and the 60s, that almost all of them had darker color on the spark plugs in the middle, compared to the no 1, and 4, or 1, and 6. ( if they had that type of intake you probably talking about here)

So I believe they jetted the carb to feed as perfect mixture as possible to the furthest away cylinders, and then the other was ok to run a bit rich. Not sure, just a theory. But there is huge difference in length to the different cylinders on these engines.

The difference we are talking about here, are probably not noticeable.
 
The free swiveling elbows are an interesting idea. Have to think about that one.

Interesting observation of the plug colors on inline engines. I think you are correct in thinking the small runner differences we are talking about probably won't make any noticeable difference. Might be different if I was building a race bike but this 83 is just going to be a sidecar tug.

Barry
 
well anyone who thinks there not a difference is just blind ...runner length makes a difference for sure ...but most oldwing deals are at at small difference ...leaks of unwanted air is the big deal ..
 
In a perfect world, the intake valve would be the same distance from the fuel/air source on every cylinder, no matter how many cylinders you have. In reality tho, it's just not possible on a mass production scale. So what we get is the best compromise they can come up with. It works pretty well in most cases. Is there improvements to be made? Soitanly there are. That's what keeps the aftermarket, and specialty markets alive. OE manufacturers have to design something that will work the best for the masses, since they typically sell to everyone that has the $$$$ to buy their vehicles. The aftermarket/specialty parts suppliers do not. They design/build what the market wants. The rest is up to us...the end user. The single carb conversions on a 'Wing is just one example of someone building a better mouse trap. :good:

Speaking of equal length intake runners..how's this for a factory produced, optional equipment piece? Anyone remember these back in the day? :mrgreen:
Pretty much useless for everyday driving, but a terror on certain race engines. And you could order this from the factory on your new car. :yes:
intake-300.jpg
 
I had 2 of those !! a 1960 and a 1961 chrysler 413 HP with the long ram intake and 2 carter carbs!! Bitchen set up, but i must say, they looked better than they ran!! NO top end and were done about 4800 rpm as the runners were too lond and small inside to flow any rpm with power! If you wanted to make power in thos day's, you used a 62 to 64 max wedge heads and short cross ram and then she would rpm!! Great Times :cool:
 
Yup....long runners give you gobs of low end, but fall flat on their faces anywhere above 4000rpm.
And yer correct...early Chrysler Cross-Ram manifold. :eek:k:
 
I like reading about the single carb stuff and watching everyone work through the issues and decided that I wanted to know what my OEM runners were doing while running. Get out the old thermal gun to test temps and was surprised! Ambient garage temp of 62 degrees, the temp at the top of the OEM runner at the boot was 54 degrees. Check at the intake flange right at the head (warmed up engine) and it is still 54 degrees!

The fan came on and I waited for the fan to cycle off and even with the heat shield, the front runners temps on #1 and #2 went up to 72 degrees but the #3 and #4 runners only went up to 64 degrees. Just a curiosity, when the bike is on the road in 40 degrees weather, it would seem that the front runners always get warmed from radiator heat better than the back runners.

I guess I was more surprised that even with the engine running at 195 degrees F at the heads, the intake runners still remained between 54 to 72 degrees right at the intake flange.

I don't know if that is useful information or not, but it was a fun thing to do on a very cold winters night! :yes:
 
it is it confirms that when gas charge is made .. loss of heat is part of the process ... so the fuel feed can be classified as a cooling system ...on days when hooch runs perfect and theres no icing going on what so ever ..the grab bar runners are always cool to the touch ....
 
Exactly. It's an evaporative cooling system hastened by the venturi effect of lower pressure. As to the runners staying cool, you have to consider the enormous volume of air/fuel mix going though the engine. Heat is trying to move up through the runners, but before it gets far it decides it will leave the aluminum and go to the cooler air and back down it goes. Heat always moves into cooler objects, but takes the path of least resistance.
 
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