Quad Carby Setup

[Twinky]

Just had a crazy idea of fitting a quad carburetor setup from a road bike onto a 4k, something like the ones the honda 750's used.

So basically an individual small capacity carby for each cylinder.

Yes some custom fabrication will be required to fit them (I can do this at work :) ) and a new intake manifold. Probably also an electronic fuel pump

for increased flow. But maybe not. but maybe. By looking at the intake on the original carby it looks too small to supply the engine with enough air to breathe, thus my inseration to modify.

On the exhaust side of things what is the most beneficial system to use? My current setup is a 4-2-1 system but only like a 1.5" system. Funny thing tho, I havent actually looked to see wether I have a catalytic converter, I assume it does so would it be good for a 2" system from that point or an entire new system from the manifold? I don't see mutch benifit with going any larger than the port sizes on the exhaust.

I'm too used to modifying newer engines that are pretty mutch bolt on mods. Carby motors are actually quite fun!

The main issue I have with the stock manifold is that it looks too mutch like a log type setup, which seems pretty primative but correct me if I am wrong.

 

Cheers guys!

Edited February 12, 2010 by Twinky

[Evan G]

i belive it has been done by a member from here (can't remember name)

 

I'm also thinking to make a custom intake manifold and use 2 4k carbies for a hot motor

[KENut]

Yeah has been done, the guy has some good photos of it.

No cat. 2 inch would be ok..

Make new intake manifold I say, don't mdify the stock one

 

Evan 4k carbys are gay, stay away from them

[BReNt]

yep they're right, it's been done. I found his thread.

 

http://www.rollaclub.com/board/index.php?s...19886&st=75

[ke71-rolla]

Quad carb for suuuuure, would be wicked, how good does it look on the 4k in the ke11!!!

[Bamboo]

Check out some early Honda sports cars. Bike type engines in cars. I know these have been done in early Civics (my second love). It can and will be done!!

[Hiro Protagonist]

Check out some early Honda sports cars. Bike type engines in cars. I know these have been done in early Civics (my second love). It can and will be done!!

 

 

Honda 1300 Coupe 9S is the one you want, 1.3L quad Keihin carbies, air-cooled, dry-sump and 87kw :) Pretty damn good for a FWD car in 1970

Edited February 12, 2010 by Hiro Protagonist

[Evan G]

i was telling a motorbike expert about how someone on the rollaclub put bike quad carbies on a 4k, he said "your better off just putting a bike engine in it!"

 

have been looking into prices :)

[Twinky]

Thats some good digging of threads guys, I get too impatient sometimes. Especially when I have these ideas racing through my head.

That car is absolutely wikedsick! I think the 900cc carbies may be a little too big tho. My boss has told me that the 750 bike carbie is an excellent idea because the carbies were made bigger (more fuel flow) because of 12,000rpm hits.

And that requires alot of fuel. So then he started to drone on that back in the day blah blah Honda 750 carbies were are very popular choice. So basically what I'm saying is that a 900cc carby setup would be better for a 1.5-6 ltr.

Okie dokie going for a pricing as soon as I can.... just need to find a bike wrecker close by.....

 

Cheers guys

[Old fella]

G`day mate, good choice..... I did it many years ago on a 1200 cortina engine in a 1961 Anglia and it worked a treat. I used CB 750 k2 carbs (1969) and made a custom manifold. Not hard to do. The one down side was that the car didn`t like to start without choke and those particular type of carbs had a lever choke located on the side. If you go ahead, take the time to look for a set that has a cable operated choke because just about all of the early bike carbs have no accelerator pump. If it were me, I would be looking for a nice simple set like CB900f `79to `83(32mm from memory) or CB 750f (30 mm from memory)

Absolutely avoid anything that has rubber diaphragms , coz replacement of diaphragms will cost your first born.

I didn`t change the fuel pump setup, but instead made a larger fuel distribution tank that gravity fed the carbs after the stock fuel pump had filled it.(illegal I think) Most bike carbs only run about 2 psi inlet pressure so if you do want to use an electric setup, start looking for an SU pump from a Range Rover and a pressure regulator. Bike carbs do like to run with an airbox, so give that some consideration too.

I have recently seen these types of carbs advertised on ebay for not much money and the same for the fuel pump.

Most or any mororbike workshop will be able to synchronise the carbs. Its a speacilist thing that is not really possible to do in a back yard situation. 4 Vacuum gauges are needed. They are actually very similar to su`s in that they use a butterfly and slide setup.

It sounds a bit daunting at first, but is very achievable for something different, so don`t give up.

 

I got the bug to do mine from watching a `61 Anglia race car at Lakeside Raceway, that had a 170 Falcon super pursuit motor and six Amal Concentric carbs.Usta go like a dog shot in the arse and the induction noise was like nothing else.

Anyway, good luck with the conversion and be sure to post some piccies at the end.(or even during)

Old Fella.

[philbey]

Don't worry too much about running without a choke though, you just need to get creative about pumping the throttle and cranking it for a bit. Other than running rough when cold, I've never found my dellortos that difficult to start.

 

As oldfella said, watch out for the Diaphragm carbies, they're CV (constant velocity) carbs. I've only ever noticed them on XS650 yamaha's and they're a nightmare to replace the diaphragms. They're also a lot bulkier than slide carbies, and they tend to hunt when trying to maintain steady speed.

Edited February 13, 2010 by philbey

[Jono.C]

theres a video of bike carbs on a 4k on youtube..

 

[Twinky]

Mechanical work does not scare me nor does fabrication. Only thing I am scared of is buying these types of things from ebay..... I bought some velocity stacks from ebay recently for my 20 valve and when they turned up they were of a horendous build quality.... A blind monkey could have machined them better. I was even very cautious reading up on sellers history and all that but still..... Got butt stuffed.... So I just forked out a few dollars more and bought them from Tweakit.net and all way merry. So during the week I will visit a parts dealer and get a price for the quads.

Someone from toyota should be shot..... I tried taking off the sump today and there are two bolts that are unreachable because of a god dam brace support for the gearbox, which means I can't get a socket in there, so I have to spend more time and take the fuker off. So I thought fukit I'll just have a beer and do it another day.

 

Cheers guys1

[philbey]

Yeh, ebay can be dodgy but I've been buying for years and only got stitched up once.

 

Look for Mikuni or Keihin quad setups of the jap 4 bangers. Lectron make carbs as well, but they're pretty rare. Also, there are Dellorto PHF motorbike carbs, but you probably won't find them in a quad setup.

[Twinky]

Hehe! Woot! My boss has kindly donated some quad carbies from his old Kawasaki GPZ 750. Unfortunately they are a diaphragm carbie, but for free I can't go wrong.

He told me that they require a thorough cleaning cause they have been sitting around for a few years. i have taken off all of the float bowls and the diaphragms and all looks good.

One of the diaphragms have a pinhole in them which can be fixed with an epoxy but will require a close eye over the years because the epoxy will be eaten away over time by the petrol fumes.

They were working when they came off so I presume they will work when I put them on. Lots of things to do before I can do that though.

Going to finish of the twinky soon and then i will start on the 4k. Updates as they come including a tutorial on how to strip the carbies and give them a good clean.

Hopefully I don't encounter something bad :) .