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What Model Year EA-81's have Dual-Port Head?


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22 replies to this topic

#1 RAVC1

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Posted 10 January 2007 - 06:16 AM

Can anyone here answer this question for me? I'm more familiar with the older generation EA-81, but now that I need a replacement engine I'd prefer the dual port or an EA-81T.

Thanks,

Rick

#2 Jerry DeMoss

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Posted 10 January 2007 - 08:57 AM

The dual port engine that you are looking for is about as rare as finding an old gsr subie here in the states.I am not really all that sure what year that engine was built but it is more than likely you won't find one unless you go outside the country.But with an ea81t you shouldn't have too much trouble with finding one of those.

#3 suberdave

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Posted 10 January 2007 - 10:41 AM

i could be wrong but i think they only came on the duel carb setup.

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#4 mikeshoup

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Posted 10 January 2007 - 12:31 PM

There wasn't ever a USDM dual port head. Anything is going to be JDM if they existed.

EA-81T heads are nice as they have fuel injector bosses. Other than that, they're the same as other 83+ heads (or was it 82+ that the larger valves came out?).

#5 GeneralDisorder

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Posted 10 January 2007 - 01:45 PM

They made dual-CARB heads, not dual port. They are still siamesed ports, but the valves are reversed like the EA82 for better flow.

Dual port heads are essencially unicorns - rumored to exist, but no one has ever seen one. The exception is the RAM performance heads - they are dual port, but they are modified stock heads.

GD

#6 Frank B

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Posted 10 January 2007 - 06:01 PM

Years ago, on the old board, someone posted pics and info about this, Yes they are rare, but they did exist. I believe the true, initial dual carb engines were dual port. That is where the aviation guys got the inspiration to make those trick dual port heads. I remember reading about it on an aviation site years ago. A guy had one, it was dual port, and it was dual carb, and he was not living in the USA. Most of his site was dedicated to talking about replicating it. Also, if I remember correctly, Subaru ran the dual port EA81 in the early rally cars. Most likely a Japan only item that none of us will ever be able to see in person. I'll try to find that stuff, but that was two or three PC's ago so I doubt I have it!

#7 75subie

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Posted 10 January 2007 - 06:11 PM

if thats the case, stratus2000.com has many of those dual carb heads.

#8 Ross

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Posted 10 January 2007 - 06:17 PM

Years ago, on the old board, someone posted pics and info about this, Yes they are rare, but they did exist.


yeah they certainly exist, i saw an engine with them a few years ago....in a jdm ea81 rx..... unfortunately the owner didn't want to sell it!

#9 GeneralDisorder

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Posted 10 January 2007 - 07:49 PM

This is the only pic I've ever found - it's of a race spec EA81 advertisement. I don't beleive these ever came on anything stock - possibly even in Japan as all the dual carb EA81 RX engines I've seen were single port. That's how us US guys can bolt on the dual carb manifold.

Clearly it's a monster, and used for rally racing. HP.... who knows but the JDM single port dual carbs were 108. I'm betting this is pushing quite a bit more than that.

Posted Image
Posted Image

The difference is clearly seen as the standard production RX dual carb has the kidney shaped blue air filter box, just with two studs instead of 3, and covers dual Hitachi carbs. This engine has two carbs (god knows what, but clearly MONSTER downdrafts), and NO manifold. It uses two seperate air filters, and in the rally cars they had dust control snorkel attachements and such. Crazy stuff, but as I said I've never, EVER seen a picture of one of these in a production car. I'm guessing because they were special limited production items, and possibly not street legal. Hard to say.

Here's your RX dual carb:
Posted Image
Posted Image

As said tho - good luck ever finding a set. Better bet is to just buy a set from RAM.

GD

#10 Matty B

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Posted 10 January 2007 - 09:29 PM

The General is correct as usual, please let me add that there were various tunes available factory with the twin carb EA81's.

I have owned a 110 (or 108) and a 120hp version.
Definately more aggressive cam cut and differently jetted carbs.

Perhaps a competition tune?.

Revved its tits right off, used to bury the tach and SCREAM.


Posted Image

#11 crazy D

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Posted 10 January 2007 - 09:35 PM

sorry to butt in on the thread but i need new heads in the near future and i was wondering what should i do....i want power....but i need them cheap....i have an '81 ea81 engine w/ 125k on it....can i use those heads?

#12 GeneralDisorder

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Posted 10 January 2007 - 09:40 PM

sorry to butt in on the thread but i need new heads in the near future and i was wondering what should i do....i want power....but i need them cheap....i have an '81 ea81 engine w/ 125k on it....can i use those heads?


Not if you want power. 80/81/82 EA81's came with smaller intake valves. 2mm difference in valve size. You need 83+ heads. They are all the same beyond that, and performance heads like the RAM dual's are extremely expensive and require custom manifolds.

GD

#13 Frank B

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Posted 10 January 2007 - 09:59 PM

I was a bit off on what I posted earlier. What I was thinking of was the early or Subaru racing dual carb engines. They had a larger intake port in the head but it still was a siamese port for the two cylinders. It wasn't round or oval, it was more like an 8 shape. Said to have an insane cam and compression numbers to make crazy power(for an EA81).

Short of buying some SUB4 heads with the matching intake, I'd say your out of luck.

#14 daeron

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Posted 10 January 2007 - 09:59 PM


Revved its tits right off, used to bury the tach and SCREAM.


I love it :grin:

Those carbs in the pic that GD posted, of the dual port head (not the standard dual carb setup) REALLY REALLY LOOK ALOT like sidedraft Solex/Mikuni carbs that came on datsun roadsters as a performance option.. very similar to the weber DCOEs that are another popular datsun performance carb.

Mikuni is a japanese firm that made knockoff Solexes.. Solex being a British carb (I think?)

Posted Image

There is a pic of the underside to give you an idea.. google image search mikuni +datsun and you should have plenty to look at.

A guess, but probably a good one. The sort of thing my dad calls a swag.. Sophisticated, wild-a$$ guess.

#15 75subie

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Posted 10 January 2007 - 10:07 PM

your gonna also need some taller gears to match that power:grin:

#16 Ross

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Posted 10 January 2007 - 11:28 PM

This is the only pic I've ever found - it's of a race spec EA81 advertisement. I don't beleive these ever came on anything stock - possibly even in Japan as all the dual carb EA81 RX engines I've seen were single port. That's how us US guys can bolt on the dual carb manifold.

Clearly it's a monster, and used for rally racing. HP.... who knows but the JDM single port dual carbs were 108. I'm betting this is pushing quite a bit more than that.


GD


yeah thats the one i saw in a rx.... may well have been aftermarket of course. I bet someone would pay a lot of money for one of those.....

#17 Matty B

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Posted 11 January 2007 - 12:03 AM

I was a bit off on what I posted earlier. What I was thinking of was the early or Subaru racing dual carb engines. They had a larger intake port in the head but it still was a siamese port for the two cylinders. It wasn't round or oval, it was more like an 8 shape. Said to have an insane cam and compression numbers to make crazy power(for an EA81).

Short of buying some SUB4 heads with the matching intake, I'd say your out of luck.


This is an awful photo of the exhaust port before rebuild,
I tapped the blank and installed a third stud in each head for the header flange.
I also hand ported the intake and exhaust openings and the manifold to match.
..... it almost breathed like I wanted, but still no torque to speak of.
Posted Image

This is a head after planing.
I was not the first to plane this head.
Posted Image

Opposite valve position from a normal EA81

#18 GeneralDisorder

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Posted 11 January 2007 - 12:33 AM

A guess, but probably a good one. The sort of thing my dad calls a swag.. Sophisticated, wild-a$$ guess.


They do look similar, but remember the EA81 picture clearly has them as downdrafts, not sidedrafts. Mikuni's are also used on many motorcycles - great little carbs avalible in some gigantic sizes. The Bonnevile Justy GSR used three 40mm mikuni's on a 997cc engine. :eek:

GD

#19 naru

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Posted 11 January 2007 - 04:00 AM

They do look similar, but remember the EA81 picture clearly has them as downdrafts, not sidedrafts. Mikuni's are also used on many motorcycles - great little carbs avalible in some gigantic sizes. The Bonnevile Justy GSR used three 40mm mikuni's on a 997cc engine. :eek:

GD


They look like Weber 40 IDFs w/sube specific airhorns to me.

#20 daeron

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Posted 11 January 2007 - 04:33 AM

I failed to spell it out in my first post, because i got distracted looking for a pic tp link to....But my point was, I bet they are mikuni downdrafts. they certainly look like no downdraft weber I have ever seen. The primary reason I make the guess is, that was a common "weber-like" carb for japcar maunfacturers to use in the 60s and 70s.. triple solex/mikuni 44's are viewed in a higher light than the same sized webers.. I cant remember who, but one of them had jets available only in increments of 5.. i am guessing that likely to be solex.mikuni, but my carb knowledge is all a little more abstract than it could be.. I have never owned a car with a carburetor. :rolleyes:

#21 Phizinza

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Posted 11 January 2007 - 04:41 AM

Posted Image

That's interesting, mine have places for 4 studs, but of cause only have two. If I were to get a new exhaust I would make it have all four. But now it's time for EJ :eek:


if thats the case, stratus2000.com has many of those dual carb heads.

I think you'll find the site is http://www.stratus2000.homestead.com
Also check out the weberized EJ22 in there :)

#22 GeneralDisorder

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Posted 11 January 2007 - 04:41 AM

They look like Weber 40 IDFs w/sube specific airhorns to me.


Yeah - they do appear to be either modified IDF's or possibly asian copies of same.

Perhaps one reason these didn't come stock is that there wasn't a good source of japanese carbs suitable for this type of setup. That, and the messy linkage and tuning with two carbs on seperate manifolds.

GD

#23 naru

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Posted 11 January 2007 - 05:39 AM

[quote name='daeron']I failed to spell it out in my first post, because i got distracted looking for a pic tp link to....But my point was, I bet they are mikuni downdrafts. they certainly look like no downdraft weber I have ever seen. The primary reason I make the guess is, that was a common "weber-like" carb for japcar maunfacturers to use in the 60s and 70s.. triple solex/mikuni 44's are viewed in a higher light than the same sized webers.. I cant remember who, but one of them had jets available only in increments of 5.. i am guessing that likely to be solex.mikuni, but my carb knowledge is all a little more abstract than it could be.. I have never owned a car with a carburetor. :rolleyes:[/quote

I`ll take that bet.Here are some 36 IDFs from a different flat 4 engine.
http://www.ultimates...70&d=1168510514




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