The
Oldcorollas FAQ
An FAQ dealing with KE1x to KE7x Toyota Corollas
Supplement to http://groups.yahoo.com/groups/oldcorollas
The heads on K motors are all aluminium, with steel valves.
There are two basic types, standard port and big port.
Standard port heads came on most motors. They have either 25mm ports
(known as a smallport), or 27mm ports (known as a standard port). The
combustion chambers are wedge shaped, the thick end of the wedge being
closest to the pushrods, where the spark plug threads in. The bowls in
these heads (specifically, the short radius) are fairly restrictive to
power.
Bigport heads came in Sprinter cars with K-B and 3K-B motors, they have
larger 30x32mm ports and a refined bowl area for increased flow, as
well
as a differently designed combustion chamber. Doug tells me the
combustion chamber of these heads is more like what's known as a
"canted oval" instead of a wedge. Some bigport heads also had water
jacket holes, to suit a matching twincarb water-jacket inlet manifold.
All these early motors have flat top pistons.
There are K motors with different heads and dished pistons, called a
heron combustion chamber. They are the 4K-E, 4K-U. All 5K and 7K motors
are like this also. Heron type combustion chambers are known to be
better in stock form, as the shallower combustion chamber provides less
valve shrouding, it's said you're looking at at solid 3-5% improvement
in power over a conventional design. The limitation being that the
combustion chamber is half in the piston, making changing its shape
drastically difficult. For maximum performance, a flattop design is
desireable, as there is only so far you can "port" a piston before it
becomes weak, of course you need the maximum performance head to go
with it. In a street application, the heron head is better, but 4K-U
and -E bottom ends aren't easy to come by, and
would be more difficult to replace if you destroyed a piston or two.
Manifold Studs / Bolts
Where possible, change to manifold studs and nuts. Studs locate the
manifolds alot better which makes it WAY easier to take them on and
off, and has also been known to solve leaking gasket problems. Bolts
are easier to strip, and just a general pain when trying to put stuff
back on the car. Early motors seem to have come stock with ALL studs,
I've seen some heads with 4 studs, most 4K heads I've seen have the
outer two boltholes as studs only.
Springs
All standard head springs are the same, 70lb seat pressure. Bigports
got slightly stronger 77lb springs.
Valve Retainers
The other major difference in the heads is the valve retainers used.
The earlier retainers are easily identified by an upside down "cup" on
top of the valve spring, sometimes they have an O-ring seal at the top
of the retainer, which is taller. These valves have two grooves, the
retainer collet fits into the lower groove. Later retainers have none
of
that, just a valve stem seal which clips onto the valve guide, which in
turn is
shorter. These valves have only one groove. The later model stuff is
the best to use, as you can run
higher lift due to the lower valve stem, and the clip on seal provides
alot better oil consumption. The newer valves and retainers will change
over onto
older heads, however the spring height will remain the same. I'm using
all newer 4K retainer gear on my
originally-early-retainer 3K bigport head.
Spark Plug Tubes
For some stupid reason, probably cheaper casting process, these motors
have a removeable alloy tube that the spark plug goes into. Every time
you tighten the plugs (such as when cleaning or changing), the bottom
of the tube deforms and squishes in to thread onto the spark plug,
disrupting the way the plug seats, eventually the o-ring seal at the
top of the
tube won't seal, and you'll get oil all over the place. Whenever the
plugs
are out, Brad came up with the idea of flipping them upside down on the
bench, putting a block of wood on top, and giving them a tap with the
hammer. I had success with some tubes that had threaded on, by filing
out the inside and just putting new o-rings on them. If all else is
lost, new tubes and o-rings are available from
Toyota, I paid $72 trade for two full sets.
Bolt Pattern
The head bolt pattern is the same across all K motors except 7K, which
has its own unique pattern of three more bolts around the pushrods,
where there are none on the older heads. This means you can put a K
head on a 5K if you want, a 3K head on a 4K, etc etc.
Torque order is as such, pushrod side on top, manifold side on bottom
8 6 1 3 9
10 4 2 5 7
It's recommended to do the head bolts up in several passes in order, to
prevent head warpage. Durapro gaskest recommend first pass 29ft-lb,
second pass 41ft-lb, last pass 49ft-lb.
Casting Numbers
Each head has a number cast into it, usually at the back between plugs
3 and 4. Here are some recorded casting numbers:
Mildport K: 45
Unknown, smaller deck height, mild ports: 4
Standard 3K: 5, 19
Smallport 3K: 25
Standard 4K: 3, 10, 57, 20
Mildport 4K - 11
4K-E: 8
5K: 24
3K Bigport without water jackets: 24010-190, 24010-141, 24010-200,
24010-217, 24010-195, 24010-155