My experience is with a TR4A which I had rebuilt
(throught a machinest) to factory spec except when it
came to Kastner's Competition Prep Manual, I had the
4A head milled close to 10:1 (the 4A now runs 8
degrees BTDC on 92 octane), and had it ported. I
BELIEVE IN PORTING! I went from 108 Hp to maybe 135+
Hp . Its the difference between a snail and a rocket
(I got 2nd gear scratch - not recommended). I also
had the valves and seats hardened (it now uses
unleaded), had the the flywheel ground, put in a "D"
rally cam (close to our 3/4 racing cam) and had the
engine balenced. Please note that I had the porting,
milling, and flywheel preperation done at a
competition shop. The 4A suffered some degration in
low end torque (0 to 2000 RPM), (2000 to 2500 RPM)
about the same, but 2500 RPM on up its a rocket. Gas
mileage suffered 20 mph as opposed to 24 mph around
town. My total cost (1990 prices) was $1900.00 (but
hay, what does a Miata cost?).
David G. Whitelaw (slasher_dw@yahoo.com)
66 TR4A IRS (being restored for VTR 2000)
--- Johntr6@aol.com wrote:
>
> Well, the engine's out and mostly stripped. The
> major discovery was tappet #8
> stuck in its sleeve and ground through by the
> camshaft! What a sight!
> Naturally, the camshaft is a goner...that "lobe" is
> 1.33 mm lower than the
> others. Curiously, I then examined the camshaft that
> came with the extra
> engine and found that it too was worn at that
> rearmost point. Then I
> remembered (it takes a while) that a few years ago I
> replaced the camshaft on
> the TR6 because the rearmost lobe (lifter?) was
> badly worn. Is this a
> congenital flaw in this engine series, due to
> inadequate oil flow maybe?
>
> Anyway, I guess I need a new cam. Should I get a
> rebuilt one, a new one, or a
> "hotter" one as advertised by Moss? Is there another
> option?
>
> I've been reading Kastner's Competition Prep Manual
> and am intrigued. Or was
> intrigued. I spoke to the machine shop today about
> shaving the head and
> matching the ports. Very pricey and he didn't think
> it would be worth the
> money.
>
> What do you all think? Kastner writes as if the
> grinding and matching
> operations could be done by hand; of that I am very
> skeptical. If I do shave
> the head, that changes the rocker"geometry" ,
> right?, meaning more machining
> of the push rods.
>
> Am I barking up the wrong tree? Since I've got the
> engine out, will pay to
> rebuild the head, will install oversized pistons,
> and have to buy a new cam,
> it makes sense to me to do what I can to boost the
> power.
>
> Your comments and opinions are as always
> appreciated.
>
> John
>
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