6 Motorcycle carbs on my Pontiac OHC 6... any ideas?

[Chrisinestes]

I'm building a hot rod from the frame up. I'll be using a Pontiac OHC 6 for power. I thought it would look sweet having 6 MC carbs on it. I've done a ton of Googling on the subject and it's been done, but it's a tricky thing. Nobody I've talked to has actually done it themselves, they just have seen it done succesfully by somebody else. It seems the main problem is MC carbs don't have accelerater pumps and aren't designed to run with much fuel pressure at all. It's a budget build, so I can't just go buy 6 new Mikuni Harley Davidson carbs at $500 each.

Has anybody here done this, or know somebody who has? Any Ideas? They wouldn't have to be MC carbs, I'd just want 6 1 BBL carbs.

Thanks!
Chris

 

[Charley Davidson]

Mikuni's have accelerator pumps, don't remember if CV's do or not. Yo may want to look at the Honda 6 cylinder carbs. Sounds cool but tough to properly pull off

 

[Sam_Fear]

My first thought is, if you've never ran dual or triple carbs, your going to have a nightmare on your hands trying to synchronize 6 of 'em.

 

[rainman]

A kid I know put some on a Honda, (car) engine, never did get it quite right!!
But he wasn't very mechanical either!! I'm sure it could be done, but probably not easy!!

And yes the CV on my harley has an accelerator pump!!

 

[sneakysnake]

If you used a carb that was designed to be stacked it might help on linkage and fuel rail supply.If not then may could steal some ideas from them.

 

[railroad]

I bought some carbs with this in mind, also. The price on the carbs was so good, I bought them on the chance I could use them. I tried to rationalize the total carb size needed by comparing cu in on the both engines and then took 75% of that figure, due to the lower rpm of the car engine. On carbs without accel pumps, I figured the intake velocity would need to the constant and fast enough that it would not need them. I do not think sync ing the carbs would be a problem, but if you have to mount them individually, as opposed to a bank, the linkage or cables may become a chore.
Good luck, keep your progress posted.

 

[Old Iron]

First off, motorcycle carbs are gravity fed so, you'll have to regulate the pressure down to around 4psi. and they are not made to be on a single manifold so you'll have to mount them with their own standoffs, you'll see that the standoffs can be removed from the cylinder head of the motorcycle in the video then you'll bolt them to the manifold you build.
This allows you to adjust each carb for idle, wide open throttle (wot) is not as critical if you make sure the same size jet is in each carb.
The carbs can be separated using a longer throttle shaft between each carb and one common throttle cable.
Here's a video on how to tune them:
http://www.youtube.com/watch?v=t0qf11BOx6o&feature=related

Good luck and keep us posted on how things are goin [P

 

[RPM]

Check out Lectron carbs and Fast by Gast. This is what they use on the fastest drag bikes.

 

[jakas66]

Another thing to think of when usin MC carbs, they must be balanced properly to each other. Takes specialty tools, specifically, mercury based based balance tubes to set them up to run eficiantly.

 

[jmlcolorado]

I've worked on 3 or 4 suzuki's with a bank of 4 carbs very similar to the photo above. They DO need to be synced together or it won't run right.
I built my own sync tool out of clear tubing (1 leg for each carb) all connected together at the bottom, filled with some colored water then the tops attached to the vacuum port on the carbs. I balanced mine all together, rode for a few months till I could get my hands on a "real" carb balancer. When I checked it, they were all dead on.

Here's a quick link about tuning:
http://members.dslextreme.com/users/bikecliff/images/carb_sync_notes.html

Actually syncing is quite easy.
I would LOVE to do this to mine!
I think the hardest part would be jetting properly and finding the right size carb.

I will defiantly be following this thread to see how it turns out!
Good luck!

 

[jmlcolorado]

Boy you got my head really wondering on this one now

Each of the carb sets I've worked on have tubes between them. They are used to ballance each out with each other. Syncing relates to making every butterfly match the others EXACTLY.
So when you build your manifold, take into account that they all will have to connect together.

The other thing is, are you setting it up to have 1 carb per cylinder?
Maybe it would be easier in the long run, and less temperamental if you built a manafold that bolts to a regular 4 barrel carb intake. That way if 1 carb isn't tuned exactly right, it won't affect the cylinder.
I think it would look pretty cool to have 8 tubes meet into 1 going into your intake.

 

[zzrodder]

I hope this isn't a dumb idea, but I think jmcolorado may be onto something. Multiple carbs is nothing new - 6 Stromberg 97's for instance. Just build a log manifold with 6 flanges to mount the MC carbs, the log manifold really helps even out slight tuning discrepancies between the carbs. Also creating a progressive linkage so it works mainly on 2 or 3 carbs and the rest kick in as you mash the throttle down could make it way more driveable. Trying to run the carbs so each feeds it's own cylinder makes for a tuning nightmare for the average guy, as pointed out previously, another reason you don't see too many guys running Weber Carbs that way .

 

[jmlcolorado]

I hope this isn't a dumb idea, but I think jmcolorado may be onto something. Multiple carbs is nothing new - 6 Stromberg 97's for instance. Just build a log manifold with 6 flanges to mount the MC carbs, the log manifold really helps even out slight tuning discrepancies between the carbs. Also creating a progressive linkage so it works mainly on 2 or 3 carbs and the rest kick in as you mash the throttle down could make it way more driveable. Trying to run the carbs so each feeds it's own cylinder makes for a tuning nightmare for the average guy, as pointed out previously, another reason you don't see too many guys running Weber Carbs that way .

I hope it's not a dumb idea too

 

[sneakysnake]

The new "Streetrodder" has a pic of Honda carbs on a inline 8.
Looks bada$$

 

[Rev Tex Devlle]

as far as sync the carbs,, a manifold that they all dump into is the best bet,, i like the harley cv carbs very tunzable as far as linkage, i have a idea, its not that hard to do, each throttle has a adjustable cable, connected to a levered axis ,, the carbs all point to the side divided evenly,, left and right,,the levered axis is a butterfly type sett up.pulls from the middle between each row of carbs