EA Head swap

[Bob E.]

I've gotta EA-71 with siamese ports. Are there any dual port heads that will work with this engine?

[Frank B]

SUB-4 heads might be what you want, how deep is your wallet???

http://www.ultraflight.dk/sub4_-_heads_and_cam__kit.html

[Bob E.]

Those are shinny.

 

Are there any heads from the factory on later model subarus I could use with benefit?

[GeneralDisorder]

No, and the Sub4 heads are for the EA81. They will not fit the EA71. There were no performance variations of the EA71 - not in the US market anyway. And EA81 heads will not fit - besides that they are not dual port anyway.

 

GD

[Bob E.]

How different is the EA-71 block compared to the EA-81?

I was under the impression the main difference was in a 7mm increase in stroke, and I would assume advances in the fuel/ignition system...but aside from the engine I have I'm a little low on the subaru knowledge...

[GeneralDisorder]

They are the same basic design, but there were changes to the block and head castings to accomidate larger coolant flow, and to incorporate the coolant by-pass that used to bolt on beneath the manifold on the EA71 block. The head studs do not line up from one to the other. EA81 heads necesarily have larger valves, but the intake and exhaust ports are about the same.

 

The stock fuel and ignition systems are about the same - the electronic distributor from the EA81 will bolt up to the EA71 without modification. But the manifold for the EA81 is longer and actually matches the EA82. Making SPFI possible on the EA81, and not on the EA71.

 

Also the transmission bell-housing changed such that the EA81 will not bolt to the older EA71 transmission. The starter was moved from the top 1200 posistion over to about the 1330/1400 position.

 

GD

[Bob E.]

how 'bout the rocker arms? Where any larger ratios made and would they fit?

[Phizinza]

There was a dual carb manifold from factory for the EA71 (yes, as well as for the EA81) but they are so rare.

Sub4 are the only after market guys that make heads for EA81's (BTW, I am pretty sure Sub4 supply Ram engines.)

Your better off just getting someone to put a WRX motor in there for the cost of getting good power out of that EA71.

The EA82t was the first production Subaru I know of without siamese intake ports. Although the EA81t heads had 2 injectors in them right? So they got around the siamese ports for that one.

 

If you want more power, I'd suggest getting your cam ground for torque or high end, putting a weber on it, and maybe giving it a port/polish. Plus a good 2" to 2.5" straight through exhaust. But really, anything over that and your just having fun building the engine, not trying to gain decent power for your subie.

[Bob E.]

...Right.

Well I'll go ahead and throw out the last couple questions I had bouncing around my head. Along with the rocker arm question; what kind of different cam grinds were offered from the factory, and would an 81 cam fit a 71?

Also has anyone ever tried to stroke a 71 with an 81 crank? are the main and rod journals the same size? in the same place? How 'bout clearances inside the block? any relieving needed? Where shorter rods used throughout production maybe from the smaller earlier engines? and lastly what about pistons? any with shorter lengths from the center of the pin to the top of the piston?

[Phizinza]

I am pretty sure for EA71's there was only 1 cam grind. For EA81's I think there was only the dual carb one and the normal one.

 

Try looking up Delta Cams or something like that, they are a US company I think.

 

Or take your cam to a shop that is fitted to grind it, and ask them for what you want.

 

EA71 pistons increase compression on EA81's slightly, they must be almost the same piston. So most of the extra stroke must be in the crank.