more heads on the way-2.5 heads for sale-valve timing input

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ssspoon@aol.com

more heads on the way-2.5 heads for sale-valve timing input

Post by ssspoon@aol.com »

OK I jumped,

Found a pair of 93 Turbo Legacy heads with seven thousand (7000) miles (they
say) in my price range. Tried to hold off and keep looking, but after
keeping my nose open for many months, I know a good price if they're clean,
and at 7K miles, I'm not likely to do much better used, and I didn't want
them to slip away.

So I'll be looking to start over with true EJ22 turbo heads, though they may
not be as sano as the later stuff, but I want easy no hassle REAL bolt on
upgrades, not bolt on then tweak this, adapt that. At least not for the
heads, I'll have enough of that with fitting a watercooler and diff turbo.

For those of you that don't know my story, I'm still sitting on a pair of
EJ25 heads that have been worked over by Dan Paramore Racing that I decided
not to use due to some turbo application issues not available in the normally
aspirated head design. Those 2.5 RS heads are for sale.

But, back to our story.

Subaru says in a 1991 a model Year Update Course
....The intake valves and seats have been reduced to 27mm for the Turbo
only....

Reduced to 27mm from what? and Why?

I always thought with valves, bigger was better.

Maybe reducing the valves reduced the weight and cost, and with a turbo
pressurizing the valve, engineering could get away with it. Shit they got
away without an intercooler. Maybe a smaller valve promotes greater velocity
and mixing. I don't really buy any of that. I have always heard of going to
larger valves for more performance. Have to be careful talking about more
performance. More racecar performance at 6000 RPM where the engine's going
to spend most of its' time?
And at the sacrifice of low end torque where I'm going to spend most of my
time? If someone can tell me the smaller intake equates to more low end or
midrange torque it would cool me out. My instinct (not always correct) is
to go larger AND lighter.

Subaru says in a 1991 a model Year Update Course
....The camshaft has a new profile designed to match the characteristics of
the turbo engine...

Now camshaft profiling is a very interesting subject.

On a normally aspirated (N/A) engine, we can sometimes gain additional
performance by varying the cam profile, so the valves open and/or close a
little faster, or lift a little higher, or stay open a little longer, or any
combination. We can also adjust the overlap, so that the intake valve opens
a little sooner before the exhaust valve can close helping to clear out the
exhausted charge.

On a turbo engine, the overlap on the intake is usually not as radical
because we can end up clearing out the exhausted charge and a fair amount of
our new unburned mix, causing a loss of performance if we're not careful.


But at least two very well known Subaru tuners sell upgraded cams for
turbocharged Subaru engines. So there may be room for improvement on our
stock valve timing too. But again we (or at least I) have to be careful not
to jump for the sake of jumping. What do those aftermarket turbo cams do?
And what is the resultant change to the engine power and torque curves?

I will let you know if I find out

Don't forget, if you are toying with the idea of upgrading to reworked 2.5RS
Phase II heads, my price is going down, was eighteen outright, thinking I'll
try fifteen. Contact me for pix and details.

Larry Witherspoon
ssspoon@aol.com
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