Topic: 1 into 4 intake, 1 cam, 4 into 1 exhaust

[AstroWing]

I am really happy with how well my SOHC is running, had to tweak the jets a few times but now it is really nice. My college student kid is setting up a small business to help other SOHC owners convert from the stock carbs to this.

 Find out more at:  www.GaryNelsonRacing.com

Riding season is here, finally.

[Vinhead1957]

Is the one carb as big as 4 in fuel volume?

[lwahples]

That intake sure looks nice,welding wise. Be interesting to see how this works out.

[AstroWing]

Is the one carb as big as 4 in fuel volume?

I did not attempt to match the area of the stock Honda carbs. My bike engine was pretty much stock but is now bored to 836, stock cam, 4 into 1 Mac exhaust. The stock engine with stock carbs had pretty disappointing acceleration and a top speed of around 100mph.  I wanted to start with a small carb and work my way up. I started with a 36 mm Mikuni. The first ride I took, I knew it was close to what I wanted. The acceleration was dramatically improved, way better than I had expected.  Then, I bored out the cylinders and expected that my 36mm would now be too small. On the first ride, the stock clutch would not hold. After installing a new clutch, I found the bike to be perfect for my use. Arm stretching acceleration and ok top end (95 mph) If I wanted more top speed I could easily put a 38 or 40mm on. But I am so happy right now, I may not touch it. I've heard plenty of reasons why this single carb and manifold won't work.. All I know is, I will never go back to those stock carbs because I gave them away.  I apologized to the guy I gave them to. My jet changes take less than 10 minutes, several pounds lighter, no leaks and in my opinion, looks better.

[Vinhead1957]

Interesting!   

[MCRider]

Auto set ups looked like that. No reason it can't work. But 100 mph top end, stock or otherwise, if its due to the carb, is unacceptable. IMO.

[Retro Rocket]

Auto set ups looked like that. No reason it can't work. But 100 mph top end, stock or otherwise, if its due to the carb, is unacceptable. IMO.

Also, POSA had a manifold like this back in the 70's, same basic set up and carb position,  Terry has one, they were known to run the 2 outside cylinders lean so i wouldn't be riding it flat out anyway, of course they work, but not as good as 4 carbs.  It needs to be remembered, the cars that ran these type of manifolds didn't rev to 10,000 + RPM...

[AstroWing]

I have been riding this bike for a few months now. I plan to hook up some EGT's (exhaust gas temp sensors)  to confirm what I'm feeling. Arm stretching acceleration. We installed a diverter inside the manifold to direct flow outward. Once I have the actual  temps, I will post the results. I have been reading spark plugs for 40+ years in race winning engines at the highest level and I don't see any distribution or lean issues here. On single carb V8 engines the furthest cylinders from the carb weren't the problem for poor distribution. It was always the two cylinders next to each other that were close together in the firing order. Remember the piston on it's downstroke with the intake valve open pulls air thru the carb. The speed of this air over the jets regulates rich or lean conditions. The manifold does not decide to send more or less fuel to any particular cylinder. Anyway, all I can say is my bike runs great. Easy to work on, in my opinion looks better. On paper, certainly a carb for each cylinder makes the most sense. If Honda had done a nicer job on the stock carbs, I would have never done this.

I gave the stock carbs away and apologized to the guy I gave them to.

[Retro Rocket]

Cool, i love the fabrication, i was just posting what i had read about the single carb set up, if you are happy with it thats the main thing.... ....

[AstroWing]

Thanks,

My bike of choice for longer rides is my Kawasaki ZX 14. I  have over 30,000 miles on mine, rode it 600 miles last weekend. My cafe racer CB750 is more for around town riding and local bike nights. I just can't believe how the little Honda  accelerates. I have no way of racing myself with both bikes but after riding both bikes on the same day I really think my honda is as fast up to around 45-50 mph. My ZX is by far stronger after that.
All I know is this Honda is perfect for me as it is right now. Single 36mm carb, 836 bore, Mac exhaust, dyna ignition and stock cam. If I wanted to ride long distances and higher top speeds I could easily go to a 38mm or a 40mm carb, they will go right on my manifold with no modifications. It may be partly because I took so much weight off the Honda, but I believe the acceleration I am feeling is the small carb.

I am open to all opinions but I'll have to argue with anyone that tells me it won't work like this.

Thanks,

[Retro Rocket]

Well, if you can get it working over 50 MPH  like the ZX lets us in on that won't you....

[kghost]

What is the advantage?

Having just one carb to fiddle with?

You say that your bike pre-mod would not accelerate.....now it does.....

Mine have always accelerated. My 836 power wheelies in the first 2 gears and does 120 + mph......

Maybe I've missed something?

[Retro Rocket]

Mine have always accelerated. My 836 power wheelies in the first 2 gears and does 120 + mph......

I love hearing this, can't wait to get my fuel injected 1000 on the road....

[trueblue]

The manifold does not decide to send more or less fuel to any particular cylinder.

It is obvious that you don't grasp what actually occurs inside a log type manifold at high RPM's.  When the air fuel mix reaches the bend where it enters the outer two cylinders, the fuel is heavier than the air and seperates out due to centripetal force.  This causes fuel sheeting on the corner of the manifold and causes the outer two cylinders to run lean.  You can't compare a V8 valley type manifold distribution characteristics to that of a log type manifold, they don't behave the same.  I would be very dubious about running it at high speed for any length of time.

[AstroWing]

I know there are a lot of smarter people around here than me. Smart people stopped messing with carburetors a long time ago because of the inherent short comings. A throttle body for each cylinder and direct injection into the chamber is better then port injectors. I'm not smart enough to make my '76 Honda direct injected with 4 individual throttle bodies.

My goals were to make a simple system that runs well, is easy to work on, reduces weight and looks good. Anyone here is welcome to question any of my goals. Please send a picture of the system you built that is better.

A person could take a SOHC Honda remove their complete induction system, install my kit and be riding in less than two hours. In doing that job, it will take you longer to remove the old parts than it will to install the new parts.

I posted a picture of an old Offy manifold that won't work either, just does, somehow. Technology is certainly moving past dinosaurs like this, I'm very happy with the technology on my ZX14. I just have different goals for my SOHC Honda... I feel met those goals. If pure speed is the goal, I'll ride my ZX. I just don't feel like trying to make my Honda in a ZX. I wanted something different for my Honda.
Check it out. www.GaryNelsonRacing.com

[70CB750]

And what part of it suppose to look pretty?  You should move this thread to Service Offered:

http://forums.sohc4.net/index.php?board=50.0

[kghost]

Well you've probably reduced the weight......

What's the decrease vs 4 carbs?

[Retro Rocket]

I know there are a lot of smarter people around here than me. Smart people stopped messing with carburetors a long time ago because of the inherent short comings. A throttle body for each cylinder and direct injection into the chamber is better then port injectors. I'm not smart enough to make my '76 Honda direct injected with 4 individual throttle bodies.

My goals were to make a simple system that runs well, is easy to work on, reduces weight and looks good. Anyone here is welcome to question any of my goals. Please send a picture of the system you built that is better.

A person could take a SOHC Honda remove their complete induction system, install my kit and be riding in less than two hours. In doing that job, it will take you longer to remove the old parts than it will to install the new parts.

I posted a picture of an old Offy manifold that won't work either, just does, somehow. Technology is certainly moving past dinosaurs like this, I'm very happy with the technology on my ZX14. I just have different goals for my SOHC Honda... I feel met those goals. If pure speed is the goal, I'll ride my ZX. I just don't feel like trying to make my Honda in a ZX. I wanted something different for my Honda.
Check it out. www.GaryNelsonRacing.com

I think i made the point earlier that you can't compare car engine manifolds to anything on a bike, the bikes operate at revs the cars will never see, this effects the rate of flow immensely, besides, that log six cylinder "old Offy " manifold is no where near as efficient as the triple carb set ups we used here on our six cylinder performance applications....Look up GTR XU1 and E49 Charger for example, both performance six cylinder cars running triple carbs.... Here's a pic of the Chrysler E49 engine with triple 2 barrel webers, these engines came stock with these carbs and were as fast as the 5.8 liter ford Cleveland HIPO V8{GTHO}, the E49 6 was 4.3 liter.  The E49 effectively had a throat per port



I know you aren't going for all out speed, i was just commenting on the car log manifolds....

[kghost]

Awesome pic retro

[OLD BILL]

  If Gary says it works, I  believe him. He was / is one of the smartest cats I ever met in the Nascar garage. I may try this on my 78F build, gotta be easier to tune.
 

[AstroWing]

Love the picture of the engine on a dyno. Back in the 70's before we had much in the way of reliable sensors we would turn off the lights in the dyno room and look at each header tube for how far the header tubes were red. The engine in the picture looks slightly leaner on the front cylinders. Most engines in those days had much worse distribution. Now days with 02 sensors and ECU's, we don't need to use the old analog ways. Some how our engines ran at high RPM and won races.. We even ran full throttle for extended periods. Really did.

[Retro Rocket]

Love the picture of the engine on a dyno. Back in the 70's before we had much in the way of reliable sensors we would turn off the lights in the dyno room and look at each header tube for how far the header tubes were red. The engine in the picture looks slightly leaner on the front cylinders. Most engines in those days had much worse distribution. Now days with 02 sensors and ECU's, we don't need to use the old analog ways. Some how our engines ran at high RPM and won races.. We even ran full throttle for extended periods. Really did.

You sure did, but a a lot lower revs than a bike....    Getting back on track though, what sort of fuel economy are you getting..?

[AbbyRider]

I'd be curious to know performance vs Cycle X's dual Mikuni setup. Roughly the same price. I'd be happy to test 'em both out if someone wants to send me the setups.