Anyone run a single carb?

[kyle.quamme]

Thank you for all of the information on here. Since I only have a 550 I'm thinking something that can flow 180CFM will be plenty. I am pretty sure I am going to go ahead with this project. My father owns all of the tools that I will need to make my manifold and I know that once I get it tuned in, I am going to be really happy with the dependability.

[Dan Ruddock]

You won't like it!! Will idle like a over camed V8. Dan

[kyle.quamme]

You won't like it!! Will idle like a over camed V8. Dan

Well I guess I'll just have to figure that out for myself now, won't I?

[Nerobro]

I'm fairly sure even an oversized single carb willl idle better than our racks of carbs. more consistant airflow means better metering. less reversion. less of everything that makes carbs unhappy. Except that a wet manifold ends up sucking fuel out of the airstream.

[drhach]

[QUOTE=Nerobro;625185]While that is "true" that's also assuming zero intake vacuum, and 100% VE.
You're right about the assumptions that I made. Considering that an engine without a compressor is not 100% VE the carb might be on the big side. Also, I'm not sure how much time anyone spends at 10000 RPM. Obviously you need when you want to operate at that RPM. Vacuum can be increased through restriction if the carb ends up being too big. As is the case with most formulae, it only gets you in the ballpark.

Please post a report how this works out. I'm curious to see how it goes.

[kyle.quamme]

My father is insisting that I make a header with tubes as close to equal length as possible, so he won't help me fabricate my original design, but from what I've gathered, it won't really make a difference. :? I'll try to make it happen but he seems dead set on making me stay with the setup I have, and well, I'll have to unless I have access to his tools.

[49er]

My father is insisting that I make a header with tubes as close to equal length as possible, so he won't help me fabricate my original design, but from what I've gathered, it won't really make a difference. :? I'll try to make it happen but he seems dead set on making me stay with the setup I have, and well, I'll have to unless I have access to his tools.

Your father is right. You should try to get the inlet tracks as close as possible to equal length. If you don't, you will compromise performance.

The timimg of sound resonance is almost a beneficial on the intake as it is on the exhaust. All purpose built performance 4-1/extractors, are designed with equal length headers. The correct tuned length, back pressure and sound resonance is the key to their performance. If you lengthen the intake tracks, you will reduce the rpms where your maximum HP is produced.
Some performance 2 strokes, fitted with expansion chamber exhausts, produce over 1/2 a bar (7 lbs per square inch) of vacuum at the port window/crankcase by cleverly utilising the effects of soundwaves.

[Nerobro]

There's a lot more to it than just that.

Equal length is HIGHLY important.

Tuning for resonance is much more difficult. As diameter changes the frequency it responds to. So does length. As does temprature, and vacuum level.

Now, you get to throw in the fact that you're running a wet manifold. So length is almost more important than tuning. Having crap mixture reach your combustion chambers is worse than not having good resonant tuning.

This is a situation where trying to copy a good wet 4cylinder manifold would be your best bet. :-) Problem is.. there aren't a lot of good 4 cylinder manifolds.

[49er]

There's a lot more to it than just that.

Equal length is HIGHLY important.

This is a situation where trying to copy a good wet 4cylinder manifold would be your best bet. :-) Problem is.. there aren't a lot of good 4 cylinder manifolds.

Another 2 good reasons to seriously look at a sidedraught twin choke setup.

[drhach]

Your father is absolutely right about the equal length intake runners. There is a formula that you can use that will optimize the length according to your chosen inlet diameter and which RPM you would like to boost. Unfortunately equal length runners only give you an increase for one area of you RPM range. That's not a bad thing though. You might want to also consider adding a plenum or an air box. That would actually give you something to mount the carb to is if you want a single and you could still have equal length runners. You could either do a side inlet or a top mount. I think if you did it right you could stuff it all under the frame and it would look pretty good. You may need to experiment a little but, the right size airbox will get you some pretty good throttle response.

[lecroy]

Notice the lengths...

http://cgi.ebay.com/ebaymotors/FORD-300-6-cylinder-4-barrel-INTAKE-MANIFOLD-CLIFFORD_W0QQitemZ230121367869QQihZ013QQcategoryZ42606QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

http://cgi.ebay.com/ebaymotors/Clifford-6-cylinder-Intake-Manifold_W0QQitemZ230120559111QQihZ013QQcategoryZ36474QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

http://cgi.ebay.com/ebaymotors/Chevy-235-Intake-Manifold-6-Cylinder_W0QQitemZ290104109743QQihZ019QQcategoryZ34202QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

http://cgi.ebay.com/ebaymotors/chevy-inline-6-cly-four-barrel-intake-manifold_W0QQitemZ330112469447QQihZ014QQcategoryZ38634QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[relic-rider]

One thing that I thought I'd mention. Won't the velocity of the air flow on the end cylinders be decreased unless you taper down the size to the end inlets. Or just leave the inlets the same and make the manifold opening larger by the carb for the feeders for the end carbs. I really don't know much about airflow, but we use this principle for metal flow in our aluminum die cast dies at work.

[kyle.quamme]

Notice the lengths...

http://cgi.ebay.com/ebaymotors/FORD-300-6-cylinder-4-barrel-INTAKE-MANIFOLD-CLIFFORD_W0QQitemZ230121367869QQihZ013QQcategoryZ42606QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

http://cgi.ebay.com/ebaymotors/Clifford-6-cylinder-Intake-Manifold_W0QQitemZ230120559111QQihZ013QQcategoryZ36474QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

http://cgi.ebay.com/ebaymotors/Chevy-235-Intake-Manifold-6-Cylinder_W0QQitemZ290104109743QQihZ019QQcategoryZ34202QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

http://cgi.ebay.com/ebaymotors/chevy...QQcmdZViewItem

Exactly what I was thinking.

[drhach]

Exactly what I was thinking.

I don't get it. What's the reference to? That they are all equal length? Or that he should buy one of those cast iron manifolds for his bike?

[lecroy]

"I don't get it. What's the reference to? "

"Notice the lengths..."

Yea, I was thinking that Ford manifold would bolt right up....

My point was that the distance from the inlet to the outlet ports are not the same, however the distance from the plenum to each port appears matched.

This would be an interesting problem to model.