HIMNI Racing

I'm thinking about adding a little 4 carb action to my wifes 83 GSL.

I know I could always go with a Holley or Weber but, this would be sweet to do.

I would make the intake mani out of 6061 aluminum, Fab the lower plate to bolt to the block, using the stocker as a templet for mountting holes and ports. Then use 1"-1 1/2" T-6 mandrel bent tubes as the runners.

I have many extra carbs. The ones I would use for this are from a 900cc Super bike. They would bolt/clamp to the runners as they would on the bike, float boles parallel with the ground.

Fab the throttle cable bracket.

It wouldn't be a prob to make the mani or to have it match up with the carbs.

The main prob. I think I would have is injecting the oil.

I'm not sure of the size of each carb. Some place in the range of 30-40mm each.

I can get the jets in all kinda of sizes.....I think stock is 120 X 4

what do you guys think?

Here's a pic of the intake side of the cabs

HIMNI Racing

Outlet.......

81Rex6port13b

interesting... a bit big tho... can you get a way with 2?

one for each rotor.

rototiller1

That will not work! The float bowls are not large enough,
it will fuel starve at anything above idle

Jon_Valjean

That'll go great - really unleash some horsepower. You are running a bridgeport, aren't you?

Oil injection isn't a problem, just mix a little in with the petrol when you fill up.

HIMNI Racing

81Rex6port13b, Can't brake them in 1/2. It's all one chunk. When you say to big, what do you mean? If the fuel is there for the mad amount of air..........

rototiller, I don't think it would. Each one of the bowls are about the same size as the bottom of a soda can about a 1" high. One main fuel feed. rear hose in the 1st pic.

Jon_Valjean, not even a street port on this one.

What size are the stock jets in the stock carb?

Give me more input, flood me .....

Sterling

If you calculate the bike displacement and multiply by high rpm (divide by two if it's a four stroke) and copare the # to the 12a @ 1146cc x 8400rpm, that'll tell you if you're in the ball park.
The stock jets are .92 and 1.60 mm.

I think you will have serious low-end loss, both by the size of the chokes and the short runner.

HIMNI Racing

lets see,

(900cc, 4 stroke, 4 cylinder w/11,000 rpm red line)

Carbs from: 900cc X 11,000rmp = 9,900,000.

12a : 1146cc X 8,400 = 9,626,400.

Sterling, is that right?....what's your thought, will it work?

wwilliam54

put a vacume operated betterfly under the 2 middle carbs with a short h-piped runners to the middle intakes

then have the outer to intakes running through smaller diameter, longer runners

the primaries and secondaries would be reversed, but it should work great

wwilliam54

the intake volume for the bike should be half that since its a recip IIRC

Critoris

Yeah, since the bike displaces 900cc's in two revs, your equivalent displacement would be 2292cc's from the 12A.

Sterling

That just tells you if it enough carb.
I still think you'll have no low end whatsoever.

HIMNI Racing

I don't need to drop any low end. We suffer from enough of that with the rotary. This is the same reason why I put a to4b on my 10th ann and not some big dirty snail.

You said you think I'll drop it because of the size of the carb's runners & choke size? When you say choke, are you talking about the butterflys? ( just one in each carb)
How long should they be? I mean, They are about a inch longer then a coke can, that's from intake top and to outlet bottom.

HIMNI Racing

oops, devide by two. I forgot.

HIMNI Racing

See, with my TII being about done (dyno time needed to tune the Microtech) & ready to hit my 400+ RWHP mark, I thought I would put some time in my wifes 1st gen before moving on to her 90 n/a.

I'm a EFI guy all the way, but I'm not going to take the time to fuel inject the FB. I will drop a 6 port in it after the n/a is done, but I'm going to carb it too. That will not be for another 4-6 months though. I just wanted to add a little extra ***** to the 12a before the 13b goes in.

If I don't do these carbs, then I guess I could just get a webber or Holley lined up for the 6 port and just leave the stock carb and mani in for now.

But, wich of the two should I go with? What's the up and downs with the two diff carb and mani set-ups?

HIMNI Racing

I think I'll go ahead & do it. If it doesn't work out like I hope, then I'm only out the price of the aluminum stock and some time.

karism

HIMNI Racing : I like the idea!I thought of the same thing a while ago

Besides,Bike carbs are easy to tune!

Torque will be higher up the rev range ,but get a lighter flywheel...!

Great Idea!

Karis

bill Shurvinton

If the butterflies are around 32mm then 4 will be about the same as 45DCOE in terms of area to give you a reference for how they will behave. What you are attempting there is very similar to some plans I have for the same but using bike EFI throttle bodies. The aviation boys have been using bike carbs for quite some while so, provided you know how to tune those little mikunis I see no reason why they shouldn’t work