I absolutely agree with everything that has been said. First, the power
band for a supercharged motor & a turbo charged engine are different,
although improved turbo designs have widened the lower rpm power range.
I can only speak from my SC experiences. When I first decided to attempt
a SC engine I pulled the motor, disassembled it & sent it to a local
speed shop to rebuild & assemble it for me. Up to this point I have
always worked on my own cars but have never actually assembled an engine
from scratch. I wanted this checked & assembled by a pro for piece of
mind & lots of fun summer driving. After receiving the long block back
it was in the car & driving with in a couple of weeks. I loved the
power difference. The car ran well but never seemed 100%. I learned
allot over the next two years, unfortunately some bad stuff too. With in
500 miles of break in, the car leaked oil from the front engine
block,rear seal, & oil pan and oil pressure was anemic. With in 5,000
miles the car started to use a QT of oil every 500 miles. After doing
my homework after the fact, I realized this engine rebuild was a piece
of crap. I drove the car for two years like this until I couldn't take
it any more.
Eventually I pulled the engine again, disassembled it my self & studied
the handy work of a looser. Five out of six top piston rings were
cracked, the valve guides were knurled not replaced, gaskets were
missing & lots of RTV silicone held the motor together. The list goes on
& on. It's amazing what black spray paint can hide. There were many more
things but you get the idea.
This time I did my homework. I decided it was time to build a motor. I
found a machine shop that built pro drag engines & sat a talked with the
owner for a couple of hours. Great guy with an even better reputation. I
explained what happened with the previous motor & I wanted him to do the
machine work & prepare the block, crank & head, I would do the complete
assembly. This way I could check everything & only blame myself. I will
say that it was the best experience mechanically I ever had. I read
about setting a crank, installing pistons, rings but never actually did
it. By assembling every part I saw things that could be improved as I
put it all together.
To make an all together long story short, this motor has about 15,000
miles on it. It doesn't leak a drop, uses a quart every thousand miles &
runs really strong. I don't abuse it but it has been driven the way was
intended too. The key to any engine project are quality parts (new
camshaft, just kidding Randall :-) ) preparation & execution. If a
great mechanic puts together an engine with bad bearing clearances,
poorly ground crank journals & sloppy tolerances it's going to be a
piece of crap no matter what.
This motor uses 6-7 lbs of boost , produces most of it's torque & HP
between 2,500-5,000 rpm. Keep in mind that a typical normal induction
high performance motor must increase it's compression ratio & use higher
rpm's to create HP. I am using 7.75:1 stock compression & can pull a
tree out of the ground at 2,500 rpm. My boost & increased load are
momentary. A high compression engine is under additional load stress all
the time & especially at higher rpm. Time will tell what long range
effects will have & I will be honest & give you the facts, good or bad.
Keep in mind though that Dick Taylor has been running a turbo'd 6 with
motors lasting well over one hundred thousand miles at higher boosts
than I'm using.
--
Mitch Seff
Oceanside, N.Y.
75 TR6SC
http://www.triumphowners.com/384
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