Hi Bruce:
Your post (below) reminded me of this experience, my first in engine
rebuilding, and please recall that my recollections (technical memories) are
from 40 years ago, and I was an inexperienced youngster then, hence the
explanation given may not be completely accurate. But the essence is
valuable information.
When in high school, 1960, at age 14, a young, fresh out of college, a
colleague of my fathers at Griffiss Air Force Base had an early 50's French
Simca, which threw a connecting rod. Of course this was in the middle of a
horrible blizzardy winter, and of course my father offered our garage for
the rebuild. This meant our '56 Dodge had to sit outside behind the single
car garage, which I had been delegated (and enjoyed keeping)to keep snow and
ice free (as well as the driveway) in our Mohawk Valley, Upstate NY home.
We had to go to Utica NY, a 20+ mile drive from our home in Rome, NY to the
Chrysler dealer to order parts. There were few options in internal
components as I recall. In the meantime, we disassembled the engine. Several
weeks later, upon receipt of the new bearings, I was delegated the important
job of installing the bearings properly in the bearing caps,and installing
them. With specific and detailed instructions from my father, which included
how to place the plastigage on the bearing cap (exactly perpindicular only,
and not 'stretched'), I was to carefully place the assembled bearing cap
onto the rod bolts (the rod top bearing installed and pressed onto the crank
from above by pushing down the piston-slowly and gently, so as to not
'scratch' the new bearing), tighten the bearing cap nut (with the locking
washer installed) to EXACTLY the specified torque. Then I was to undo the
nuts, and careful remove the bearing cap, observe the spread plastigage and
compare it to the scale. Somehow three thousands clearance rings a bell. Now
this was in the winter- with howling winds and blowing snow outside, 10-20^
temps even inside with only a small electric heater.
Job completed, we go to start the engine- and all we got was a repeated
'Thump' -'Thump'- 'Thump' when engaging the starter..
The engine would not turn over, yet the starter would spin fine off the car.
My father, an experience engineer and mechanic since his Army Air Corp Days,
knowing I had the PLASTIGAGE proof of proper spec, was convinced they gave
us undersized bearings. So another disassembly, ordered the next size
bearings, and repeated the entire process. This time the engine started and
ran like a dream.
I asked my father how he knew it was the bearings. He said PLASTIGAGE only
measures the center specification of the installed bearings; where the
bearing and the crankshaft meet, the areas were the two (upper and lower
halves)bearing interlock, adjacent to where the the connecting rod bolts
are, have less 'give'. He said if it was summer, maybe we'd have been OK,
but since it was winter, and the engine need to breakin, we needed to make
sure oil would flow and protect the bearing surfaces-all areas of the
surfaces- and the crankshaft, especially at start up, for this was the most
critical time for wear. Especially with new bearings, we didn't want to
'score' them, So the wise thing to do was to re-do the job with slightly
more clearance.
Our family friend ran that car another 125,000 miles. Herb lives in Oregon
now, long retired from the Gov't service. We linked for the first time in
over twenty five years this summer on my Jensening Across America trip ( I
bought a '75 Jensen Interceptor Convertible in Vancouver,BC; and my wife and
I drove it home to Maryland after a week of serious prep in Seattle). We
joked about the 'MOPAR' reunion (the Jensen is Chrysler 440 powered).
Shortly thereafter, as my scoutmaster we took a '54 TR3 (with thin plywood
floorboards) on a Boy Scout camping trip(My first Triumph experience). At
age 76, he still drives a VW min-van and a Honda.
Bruce, be very careful with the PLASTIGAGE, use assembly lube on the final
assembly of all internal engine components. I'm sure you'll have years of
dependable enjoyment and pride from your diligent work. And make sure you
have the proper bearings given the crankshaft work.
Enjoy that TR7!
Sherman
Sherman D. Taffel
Columbia MD
'65 TR4
'72 Jaguar E-Type Ser III FHC (V-12)
'76 Jaguar XJ12C (wife's)
'89 Jaguar XJS Convertible
'96 Jaguar XJR 4.0 Supercharged Saloon
'75 Jensen Interceptor Convertible
'76 Jensen GT (J-Healey GT)(Getrag 5 speed)
'86 Pontiac Fiero 2M4 (wife's)
'86 Pontiac Fiero 2M6 SE
'89 Dodge Daytona Shelby 2.2 Intercooled Turbo (5 speed Getrag) T-Tops
'96 Dodge Caravan 3.8 ES Touring suspension, Wood Trim, Sunroof (wife's)
Date: Sat, 14 Oct 2000 18:49:11 EDT
From: Eganb@aol.com
Subject: TR7 BFH #7
The continuing saga of the TR7 with the Bearings From Hell continues....
Well, there was a delay getting the crank turned, since the T. Hoff crank
man
was sick for about a week, but I finally picked it up on Friday and they
only
had to take off .010, and the bill was only $60 and the crank looks fab.
AND
they introduced me to PLASTIGAGE Clearance Indicators which I had never seen
before -- leading the T. Hoff guys to roll their eyes at me trying to
rebuild
the TR7 -- in a half-joking sort of way.
For those of you as in-the-dark as I was, this stuff is nothing more than
what looks like a stiff piece of dental floss. you take a half-inch or so,
and place it on the inside of one of the new bearings, then put in the
crankshaft and tighten down the bolts for that one journal to the right
torque. then you take it apart again, and retrieve what is now a flattened
piece plastigage and measure its width. The more it is flattened, the less
clearance you have in the new assemble, and the TR7 manual should tell me
how
much clearance I should have. In this way, you can make sure that the newly
ground crank and new bearings are going to have enough oil flow. Really
neat
trick.
Apparently race car mechanics check every journal this way.
As always, thanks for the help.
Bruce
1980 Inca Yellow TR7 5-speed convertible
Chapel Hill, NC
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