multiple bike carbs

[mrloboy]

I am building a 1928 Model A "rat-rod". The engine is a '55 270 CID HEMI. I would like to custom build an intake manifold (the easy part!)and use multiple carbs. My Idea is to make a cross ram style manifold and run single carbs for each cylinder. My thoughts are to use cycle carbs and jet them according to the required flow of each individual cylinder. Anyone tried this before, or am I just crazy for considering it!   rj

[Bib_Overalls]

No, I don't think you are crazy.  But I do think that the complexity of it all; sizing, linkage, adjustments and synchrization, will be too much to overcome.  If you can sort it all out it will be trick!!  Something like this can get out of hand and consume time and resources better spent on getting your rod running and on the road.  I'd get the old A Model rolling with a small 4 barrel.  If you still want the multi carbs you can revist them as an upgrade project.  I want 3 twos on my roadster so bad I see them in my sleep.  But I need interior and some other upgrades more right now.  And the deuce runs just great with the single 4 barrel.  So the trips can wait.  I'm crusing now.

[purplepickup]

Rick, your question brings back memories of a post on the old, old RRT about 5 years ago about using motorcycle carbs that was one of the classics.  I'm dumb and got CRS but some of the people are still here that might remember what the concensus was.....two banks of 1200 Suzuki carbs??

[mrloboy]

Hi George;

The 1200 Suzuki set up is exactly what I had in mind., although I am more familiar with Honda Multi set-ups. I am open for suggestion as to which units would may work best. Using two banks of "4 carbs" should not be hard to work with. They can be set using 8 individual vacuum gauges. The linkage from the bikes should simplify the job. One only needs to join the two separate banks.

How would one determine the required CFM of the engine and determine the proper carbs for the application. Where should one start with jets? Fabricating an intake is the easy part for me, but how long should I make the runners and how many other characturistics do I need to consider in building the system?

Steve;

I agree! A 4brrl would get the "A" on the road and that will likely be the case for the first portion of the cars life, but, hey! we have a gazzilion feet of snow here for the next while and that gets a guy to dreaming! The engine is on a stand here in the Rod Shop and on an evening or two, we could easily fabricate an intake manifold, fire the engine up and play with the settings. If it isn't read to go come "cruisin' season" we can always bolt on the single carb for the summer. It's only a set of gaskets away!

I want the car to work well, but performance is not a major goal. Visual appeal and uniqueness is what I would like to convey. rj

[Ralph]

Hey Rick!
You got a frame done for it yet? How far along are you?Or is it just an engine on a stand, a junker in the yard, and a dream - like my Model A/500 Cad project!
Answering your question from a previous post - I sold my truck to a guy in Moorhead, MN. I'm still driving the 41, and I'm working on my wife's six cylinder 68 Camaro.
Oh yeah, and the motorcycle carb thing - ARE YOU INSANE? (Yes, you are.)
Ralph

[autocol]

i have not read the whole thread, but there's a fairly big discussion on the australian hot rod forum that's probably worth a read...

you can find it here...

[1FATGMC]

The engine is a '55 270 CID HEMI.

This is purely a guess, but since the 270 Hemi would be about 500 cc per cylinder then a good place to start might be to look for a carb that would be about the right size for a 500cc cylinder.  The Suzuki ones are for cylinders that are about 300cc's, but then that motor is a lot more effecient than the 270 Hemi probably is, so maybe those would be a good place to start.

Let us know what works if you do proceed down this path.

c ya, Sum

[mrloboy]

I agree that the 300cc comparison would be an excellent place to start. The Hemi would be running at a much lower RPM than the cycle, therefore, I assume the CFM requirement would be considerably less. I was guessing that at 50% of the RPM would translate to 50% of the CFM, resulting in an approximate equivalent to 250CC per cylinder cycle carb. Does this make sense?

The link to the aussie thread is quite helpful, but I am not sure how applicable it is in comparison to the small V-8 I am using. Any ideas?

Will I run into problems running a cold manifold with no heat generated to assist in fuel atomizing. Will the high humidity of our summers translate into freezing problems? We do have freeze-up problems with gas regulators on our wire welders on hot summer days with high humidity. Can I expect the same on this set-up? Cycles don't seem to have problems, but then again, I am a car guy, not a bike guy!

Ralph! You know my ecentricities!    rj

[Ohio Blue Tip]

Go for it!  Back a long, long time ago, in a town far away, I was in to dune buggy's.  Back then, it least in Michigan, most buggy's were just cut down VW pans, so I started with one of them.  Well, being a young Hot Rodder, that wasn't good enough, so I built a rail using 1" square tubing and it was one of the first rails ever run at Silver Lake (Silver Lake, MI is a big set of dunes on Lake Michigan about 50 miles north of Muskegon)  Of course the stock VW engine (36HP) wasn't good enough, so I added a Porsche crank (stroker) and a fabricated tubing manifold and used 2 Honda 305 carbs and it worked very well (wheelies all the way up the dunes).
To make a long story short (too late) the pair of Honda 305 carbs were just right for the 1200 cc engine.  So give em a try and adjust as needed.

[purplepickup]

How about two sets of Goldwing carbs?  They look like they might be fairly easy to adapt and they seem to be a few around.  Here's a couple of ebay auctions.  
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2466974017&category=10066
and http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2467157289&category=35597
and http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2466378017&category=35597

[choco]

Because you are contemplating multiple bike carbs, you obviously don't have the "nostalgia" look as a priority. So why not try Electronic Fuel Injection? If you can find a Hilborn stack injection setup, so much the better, but multiple throttle bodies are a much easier option. No more worries about running rich/lean and trying to sychronise carbs. If you can get an alloy manifold, you can machine the runners for full Multi-Port EFI, but if using a cast manifold, go TBI. I still think the stack injection is the best bet, though. I have just written a book on this very subject, you can get it from Larry. Try www.graffitipub.com.au

[bcal]

From my own experience I'm with choco on the EFI being easier to set up.
If you can get hold of a manifold that suits quad IDAs or the like.
Buy two sets of quad Suzuki GSXR throttle bodies.($100-$200 ebay)
Adapt them to suit the manifold. (imagine 8 of the little suckers   )
Use the Suzi injectors mounted in the TBs. (no need for welding bosses to the manifold)
Run it from a megasquirt ECU ($150)

[spark]

 mmm. I have seen quad Weber (downdraft) intakes (RedLine?) that would give you 8 bases....mmm..   [no..no I must resist ! choco & bcal]   ....but it would look cool –multi carb with injection

mmm.   set up side draft with 90 degree  polished stainless elbows with flange to suit intake one end and carb base the other.
   :?      


.

[bcal]

[no..no I must resist ! choco & bcal]

Come on spark
You can do it
Just jump in.
The water's nice and warm  
We promise  

Well the more that jump in the warmer it will feel.