Thanks Bob for that intelligence. Wow - a .200" overbore....wild!
I truly am not worried considering the performance of my engine to date. But I
might not be so frisky if I had .200" bores
in there.....
I also suspect most who overbore from max spec looking for the ultimate
horsepower machine would run their engines
much harder than I will mine. I like to give it a shot every now and then, but
mostly my wife and I are just out traveling and
cruising.
Apart from the great power that comes with stroking a given block, is the shift
of the power curve down the rpm range with
a proper cam, so there's no need to rev the guts out of the engine to get some
serious power to the ground.
Long live strokers!
Dave
----- Original Message -----
From: bob@hermitagewood.com
To: dave@munroe.ca ; tigers@autox.team.net
Sent: Tuesday, December 16, 2008 3:48 PM
Subject: RE: [Tigers] Machine shop questions
Hi Dave,
I too have a 66 Mk1A Tiger and 20+ years ago I embarked on an engine
rebuild. The thick-wall-tiger-engine-block story (as told in Performance
Tuning the Sunbeam Tiger) persuaded me to have the block bored .200 over. I
should say here that the machine shop thought me mad, and that they told me
that there would be nothing left of the cylinders when it was done. They also
told me that it would take two passes to cut that much material, and I paid
them to do those two cuts.
While the block was off at the machine shop, I continued reading and
talking to others (including people at Ford Motorsport) about my project. I
heard all the horror stories (that overbored cylinders flex, have poor ring
sealing, and have a propensity to overheat) and ultimately I decided not to
risk my rebuild on an extreme overbore. It was the 1980's and nobody near me
had a sonic checker with which the thrust faces of the cylinders could be
checked. Estimated cylinder thickness looking inside the water jacket might
have been .125 (if memory serves), but this was between cylinders and not where
the thrust load of the piston applies.
So I didn't use my original block, and it still sits in my garage today.
Would it hold up under use? I honestly doubt it, I would not risk using it
then or now. The significant point is, it took a .200 overbore with a good
bit of material left. My opinion is that your .060 overbore will never have
an overbore-related problem.
Best regards,
Bob
Bob Burruss
Tiger #382000782
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