Peter Beyl asked:
> I'm planning to rebuild the engine on my 1975 TR6. From doing my homework, I
> realize that the compression was lowered to meet emissions requirements. I
> know I've got Tim Allen syndrome. I can't leave well enough alone!What's the
> most cost effective way to give my car some spunk? Oversize pistons, mill
> the head, cam? What are the advantages/disadvantages of an aluminum
> flywheel? I still want to keep the strombergs. The car came with SS headers.
> Can my head or pistons be replaced with those from an earlier model? I know,
> so many questions!
Searching the archives for a few hours will give you a tremendous amount of
information, but I'll try to answer some of your questions here.
Oversized pistons: Have a look at http://triumph.hottr6.com/TR6motor.html.
There is a lot of interest in using inexpensive, yet well-made and tough
+.020" Mazda Series E pistons, which give you 0.110" oversize (2.7 liters).
This is apparently a popular conversion in the UK and Australia. Yes, it
can be done, but to do it properly costs. The main problem is that the
cylinder walls are quite thin. I've sonic tested several blocks now, and
though 0.110" overbore will not punch through to water, the walls are 0.050"
thinner than recommended for a stock motor. Some people do this, but I
expect they will be tearing down their motor pretty soon to repair the
damage. The solution is to bore the cylinders for new sleeves. About
$1,000, plus pistons (about $180) plus machine work to the gudgeon pins.
Aluminum flywheels will eventually walk on the crank nose bolts, even if you
pin the wheel. This is probably fine for a Sunday-drive bench-racer, or
someone who will not mind replacing the flywheel, but for serious work, stay
away from them. Kas Kastner came down pretty hard on aluminum flywheels,
which resisted all his efforts to make work. In addition, the alloy wheels
weigh 11lbs, which is too light for street use. The Brits sell 16lb steel
wheels for around 350bsp. Why someone in the US is not making them is
beyond me.
AFAIK, heads are interchangeable, but have different port specs between
pre-73 and post-73, so if you want to retain the SS headers, your search
will be confined to whatever port specs you have now.
How much spunk you want from your motor depends on how much you want to
spend, and what is your intended use for the car. You can go anywhere from
a shaved head and balanced fun motor for $2,000, to $7,000 bulletproof
150rwhp 7,000rpm motor, to a $15,000 national motor.
Enjoy!
Shane Ingate in Maryland
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