Hi PeteH,
All the Subaru variants still confuse me, but I think this is generally
correct for the EJ20 turbo...
89-93 (90-94 in USA) Legacy have a less efficient port design, hydraulic
lifters, and occasionally crack
93 to mid-96 Legacy twin turbo used the then new WRX better ported head, and
still hydraulic lifters
mid-96 Legacy introduced the WRX3 head with solid lifters and over bucket
(cam follower) shims (flat 25mm disc)
Throughout all the above, there are definitely many variants of valve
material and size, and camshafts, but I am unable to advise specs. For
instance, even the cam profiles of a 98 BG Legacy are different to a 99 BH
Legacy.
The WRX STis may be sand cast (probably are), have solid lifters and under
bucket shims (size of an M&M sweet).
I would expect an WRX STi-type RA to definitely be sand cast heads.
I have actually seen and touched a bare STi prepared WRC head and Yes, the
ports can be opened up a little more than the standard version.... but not
much more. This genuine STi prepped WRC head was a work of art... nickel
plated, cross-hatch embossing on the external surfaces, hours of hand
grinding the ports out... the intake valve guide visible within the port
(what is left of it!) is knife-edged... and all for the princely sum of
approx USD15,000 for one head!, which is still cheaper than the Pro Drive
item!
A word of warning on porting... after seeing a "normal" WRX head sliced in
cross section... there ain't a lot of material to remove... as I recollect,
only about a maximum of 5mm at the flanges and 3mm deep into the corners of
the port runners.
As for my recommendation and erring on the side of being frugal, I would not
expect to find STi heads easily. A cheaper alternative would be to get 97+
twin turbo or WRX3 heads with solid lifters.
If you want to rev over 7500 rpm it would be wise to switch to the under
bucket shims as the over bucket shims tend to "walk about" off the top of
the cam follower. I suspect that this switch could be done to twin turbo
solid lifter or WRX3 heads, but may also require new cam followers (for the
shims) and valves (stem height).
I am really not certain about USA and N/A models... applying logic, the EJ25
DOHC will be the same casting as the twin-turbo and WRX... it probably has
solid lifers but may not... the cams and valves will definitely be
different. If you intend changing the cams and valves anyway... you could
probably make them into WRX3 equivalents.
John Gillon
----- Original Message -----
From: PJHARJ <
pjharj@sauk.com>
To: <
BC-BFLegacyWorks@egroups.com>
Sent: Tuesday, November 21, 2000 1:32 PM
Subject: [BC-BFLegacyWorks] cylinder heads ?
> John Gillon wrote:
>
> < big snip >
>
> >, the only significant internal mods to be made are replacing >the
cylinder
> heads with those from a WRX or twin turbo.
>
> John,
>
> I have been trying (unsuccessfully) to determine the differences between
> the available Sube cylinder heads. Rumor has it the STi heads come with
> solid lifters and better camshafts than the WRX or twin turbo? I also
> recall something about the STi/RA heads having thicker castings around the
> ports, true? Are there any port difference's between any of the models?
> What, in your opinion, would be the best head to start with for a max hp
> buildup?
>
> I thought I read that the US spec 2.5RS of '98 had solid lifters, is
that
> true? If so, is there any other US spec models that share these heads?
>
> Thanks for your help
>
> PeteH
>
>
>
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>
>
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