In a message dated 97-09-05 09:34:27 EDT, n196x@mindspring.com writes:
>Subj: Head specs
>Date: 97-09-05 09:34:27 EDT
>From: n196x@mindspring.com (Richard Taylor)
>To: fot@autox.team.net
>
>Fellow FOTers,
>I bought a junked TR-4A motor to rebuild incrementally whilst continuing to
>drive my machine. Step one is to rebuild the head. The head thickness is
>3.328in. Has this head been shaved? I plan to shave 90 thou off. Is this
>too aggressive?
>The valve seat width apprears to be only 1/8". Is a multi-bevel valve
>grind possible?
>Any other rumors, gossip or personal preferences with regard to rebuilding
>a head is greatly appreciated.
>Thanks for you help
>Richard Taylor, HSR # 96
>
>
OK, it's opinion time again...
Richard-
First and foremost question, is what do you intend to do with this motor ?
As I sit here in my jammies, I recall that the stock head is 3.330", so your
head is so close to stock that it really doesn't matter. (Measuring
inaccuracies or a minor skim could account for the minor difference).
Is this gonna be:
A race engine-
90 thou isn't really enough to be competitive, go for about 150 thou, and
open up the chambers a touch.
An autocross/solo engine-
If a dedicated parking lot racer, it still isn't enough... see above
A street racer-
90 thou is probably about all you can go here, and you will have to recurve
the dist, add some additional cooling, enrichen the carburation, use shorter
pushrods, open and balance the chambers, and watch your "driving style"
A "multi-angle", as well as cut valves will also enhance your driving
pleasure, and should be no problem with this head. You may want to pay
special attention to the "core shift" problem in the ports. The early "large
port" heads (TR3&early 4) were probably a little too big in the port
department to make useable power across an rpm range that a TR motor can
sustain, but had lovely looking ports. The later "smaller" port heads are
considered to be actually better across the board for the TR3/4 range. The
late TR4 head castings unfortunately often suffered from a mis-alignment of
the molds, resulting in a "core shift". This can be seen as a line parallel
to the port from the manifold side all the way in to the pocket, halfway up
the port wall. If your head has appreciable "core shift", it will be harder
to clean up the ports to flow more evenly.
I'm sure all of us on the list have our own theories, and could go on
forever...did I mention intakes, exhaust, cam, pistons... Tell us more and
I'm sure you'll get more OPINIONS than you can handle <g>
Gee I love spending somebody else's money for a change...
Nick in Nor Cal
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