Does anyone know the changes that were made to the three generations of heads for the EA82 ?

I assume you are refering to the three generations of EA82 *turbo* heads? To my knowledge there were only a single generation of non-turbo, single port heads made.

 

They were made succesively thicker in the area of the exhaust ports to prevent cracks between the valves extending into the coolant jacket. The problem was never adequately solved and only by controlling the mixtures to prevent excessive exhaust gas temps and limiting the level of forced induction to about 12 pounds or less are they capable of holding. Eventually the engine was outmoded by the EJ20T and attempts to solve the problems of the EA82T beyond 175 HP were abandoned.

 

Further, the last (third) generation of heads were never actually put into production engines. They were only availible through the parts channels.

 

GD

So I can assume that they all flow the same? Thanks GD

If anything I would say the earlier gen heads might flow more due to there being less material. But overall I've never heard of anyone noting a difference. There's no indication of that from Subaru either as there was never anything put out about not mixing them if the need arises. Also the valves are all the same sizes and that is likely to be your limiting factor more than the port dimensions. Porting and polishing can yeild some improvements with less turbidity in flow, but is unlikely to flow more CFM without a change in the valves themselves.

 

GD

attempts to solve the problems of the EA82T beyond 175 HP were abandoned. GD

 

so, how did they solve the porblems up to 175 hp?

so, how did they solve the porblems up to 175 hp?

 

They had access to parts that we do not and they designed the thing in the first place. Careful mixture control, timing, and boost settings via custom ECU programming. They also increased the RPM quite a bit.

 

Mind you I'm refering to the european rally race versions that semi-reliabily produced around 175 HP. That is not to say this did anything good for the engine life (it didn't), and it's also not to be intended as a hard limit to the HP the engine can make. It can make more - it just won't last very long. The EA82 engine was designed on paper - a stop-gap solution till the EJ engine was ready. It's an EA81 with overhead cams - nothing more. It does not have the crank stability, nor the head, head gasket, or mating design stability for high-rpm/hp applications. The EJ20T was computer designed from the outset for turbo-charging. It produced over 200 HP in it's first variation in the late 80's.

 

GD

I Agree, Absolutely.

 

...the last (third) generation of heads were never actually put into production engines. They were only availible through the parts channels. ...

 

I Guess That`s Why the Newer Heads for EA82`s at the Dealer, came Heavier and the EGR Passages Comes Closed!