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(Crazy Idea thread) What'll happen if...


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#1 fbh

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Posted 18 February 2006 - 09:05 PM

... I fab a second carb onto my EA82? :burnout:

Basically, take off the intake manifold, and pretty much fab one hitachi carb onto each head...

power gains? fuel economy changes?

all-out stupid idea? :-\

#2 keltik

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Posted 18 February 2006 - 09:11 PM

If it worked, you would have a seriously mean sounding suby.

Let us know how it goes if you try it :brow: .

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#3 fbh

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Posted 18 February 2006 - 09:13 PM

I'm definately gonna try it :D pick-a-part down the road's got a ton of EA82 subies, can grab a second carb from there, and I have a mate who might be able to fab me a whole new intake manifold for twin carbies.

so it's going to sound better - how about power and fuel economy? ballpark figures? 90 horse / 28mpg roughly atm.

Just a quick thought right now, if I don't want the wee pipes of coolant flowing all over the place, I could just take the chokes off?

#4 keltik

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Posted 18 February 2006 - 09:19 PM

Well as you can see from my miniscule amount of posts - im no subaru expert but we ran twin weber cars on our 74' MGB and on my brothers Ford Capri and it made quite a difference in low end pick up.

Youre on your own as far as gas mileage goes tho - it went downhill quite a bit for us. :-\

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#5 Phizinza

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Posted 18 February 2006 - 09:21 PM

I have a dual carb EA81 (its got different heads then a normal EA81, just for better flow, there more like EA82 design) fuel usage is REDICULUS. Power is WICKED, compared to..stock...

The EA81 dual carb still uses a manifold. But you could fab up the carbs direct to the heads. Alfa 33's with the flat four in them have this same setup. check out this site http://www.hbpsystem...o.uk/engine.htm and this one http://alfasud.alfis...et/asus18d.html

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#6 Phizinza

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Posted 18 February 2006 - 09:23 PM

Oh, if your not using a manifold you are going to want the carbs running togther perfectly. Other wise you might start ripping your engine apart. I dunno for sure tho.

EDIT: AND...... you will have some fun with the all the pipes and EGR stuff that go onto the manifold. Like all those vacuum leads and stuff.. But it would be a pretty sweet subie. I haven't seen any body do this before, but I have thought of it myself

#7 fbh

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Posted 18 February 2006 - 09:26 PM

you mean running together perfectly as in throttle position etc?

I thought of making linkage arms, so that the throttle cable comes on to one carb, and that carb in turn controls the other...

otherwise, just two 1" or so high adaptor plates, with a pipe running between the two?

#8 Phizinza

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Posted 18 February 2006 - 09:34 PM

The linkage arm is how its done on my engine. works well (unless I forget to bolt on one of the mounts for it after pulling the engine apart.) I am pretty sure the linkage is also how alfa done it. So its prolly the best idea. Also you need to run the choke to both. If you use auto chock you may find it won't work very good. Or it may work even better then manual. I don't really know... Also you may need to get the carbs rejetted. Adding twice the fuel may not be good for the sparkplugs or the running of the engine.

Basiclly dual carbs will make the engine run freer. You should get more power all over the rev range. Also it should let the engine rev higher. My EA81 gets to 7500 fine and I bet it would goto 8000, but I'm not game to test it. I normally only take it to 6500. And with the 2" straight thru pipe it sounds so sweet.

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#9 fbh

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Posted 18 February 2006 - 09:43 PM

Cool stuff.

I just had a look under the hood. There are one or two things that work off the vaccuum lines - the weird blue thing I posted about a while back, and the brakes.

Would it be fine to work the brakes off one cylinder bank only?

#10 Phizinza

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Posted 18 February 2006 - 09:53 PM

As for brakes: I would think so. If the brakes feel not good after the conversion you could run another line from the other head to a T and do it like that.

One of the things that runs off the manifold is the controls for your heater and the rest of the air system in the car.

I know theres alot of stuff under a carbed EA82's hood. But I bet 90% of those wires and pipes can go. Of cause it would be at the expence of fuel economy and law.

BTW I get about 13L per 100KM, thats 18MPG

#11 fbh

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Posted 18 February 2006 - 09:57 PM

sweet. Question - if I went and built the brake vaccuum line into say the #1,3 head and the vaccuum lines fail, how strong will my brakes be? would I still be able to stop reasonably quickly?

#12 Phizinza

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Posted 18 February 2006 - 10:01 PM

Do this test to find out... roll down a hill at about 30mph, throw it in neutral and turn the engine off, then try to stop. They will work, just not so well

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#13 breaffyaviation

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Posted 18 February 2006 - 11:39 PM

... I fab a second carb onto my EA82? :burnout:

Basically, take off the intake manifold, and pretty much fab one hitachi carb onto each head...

power gains? fuel economy changes?

all-out stupid idea? :-\



You need a single control rod between the two carbs for throttle,then balance your carbs.You also need to link the inlets on both sides with a small hose to balance the vacuum. If you tee your brakes off this balancing pipe it will equalize when the brakes are applied.I have two mikuni carbs with separate manifolds but only a quarter inch balance pipe ,since I dont need the brake pipe on a plane.If you are going to do this why not go the whole hog and lose the hitachis ,put a couple of webers on there.
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#14 Subarian

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Posted 18 February 2006 - 11:45 PM

You also have a coolant crossover in the manifold.

#15 fbh

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Posted 18 February 2006 - 11:47 PM

so coolant enters the manifold on about the middle left, and gets distributed to the #1,3 and #2,4 cylinder banks via tubing in the intake manifold?

Also, what's up with the little pipe squirting coolant into the bottom of the carb?

#16 leadfootracin

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Posted 18 February 2006 - 11:51 PM

use smaller carbs, the stock carb is designed and jetted for a single carb on a 4 cyl engine, 2 carbs of that size will have great topend but suck at throttle opening and midrange. my 2 cents

#17 Phizinza

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Posted 19 February 2006 - 12:09 AM

I forgot about the coolent. That's why I original dumped my idea of doing something simular. It would bi kinda hard to fab it up, but it can be done.

#18 breaffyaviation

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Posted 19 February 2006 - 12:28 AM

I forgot about the coolent. That's why I original dumped my idea of doing something simular. It would bi kinda hard to fab it up, but it can be done.


Made a plate to fit over the head opening .Drilled a inch and a quarter hole for the intake.Drilled a oval shaped hole for the coolant .Brazed my intake pipe and coolant stubs to the plate. Link the coolant pipes and tee off for thermostat and top hose.Took a few hours.Sorry I dont know how to post pictures ,wrong generation.
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#19 fbh

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Posted 19 February 2006 - 12:30 AM

I return from under the hood of my EA82. It seems that fabbing the carbs directly onto the heads (more or less) would be impossible, because the alternator's in the way.

Instead, what if I was to saw open the manifold to the left and braze on a block to mount a second carb on?

#20 Phizinza

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Posted 19 February 2006 - 12:38 AM

Thats where you need a small elbow manifold and some weber side drafts :slobber:

#21 fbh

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Posted 19 February 2006 - 12:42 AM

hmm, is there any recommended length for the piping that's between the carb and the head? if I can have it long enough I could shove the spare in the back and have a play with the extra space...

#22 Phizinza

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Posted 19 February 2006 - 12:55 AM

basicly, shorter the better. If it gets too long your fuel may get to warm. Also I would imagine you would get a slight delay in the throttle response.

#23 Phizinza

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Posted 19 February 2006 - 03:18 AM

just thought this: if your fabbing up a mount for the carbies why not fab up a new mount for your alt. Just put it in the middle like the EJ's are...

#24 fbh

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Posted 19 February 2006 - 04:29 AM

thought about that - unfortunately the p/s pump is there :( maybe if I shove the alt further over to the right-hand side, though I'd need new belts for it then...

#25 Phizinza

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Posted 19 February 2006 - 05:55 AM

Ahh.. forgot about the power steering, I don't have that one my Brat.. New belts arn't normally a problem. And seems you don't have a disty there it would be a good place to put it. (seems EA82's have the disty on the left head, not in the middle of the block.)




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