Andy,
My WAG for the missing ring is as follows: During my old drag racing
days, I built a 306 c.i. small block Chevy engine. The pistons I
bought for it had *extremely* narrow ring grooves. The piston rings
were, of course, also very narrow. The reason for this was to reduce
parasitic horsepower loss from piston ring drag (thinner rings = less
surface contact = less drag). I suspect that if this car was used
only for racing, the engine builder decided to try and get by without
the second ring to extract a few extra ponys from the engine. OR, he
may have had a few too many Bass Ales while assembling the engine and
simply forgot the second ring on #2.
FWIW, I have known of a few racers that use special two-ring pistons
with good success.
As for the nylon bushing in the connecting rod holes, since you said
the pins are floating rather that press-in, I suspect these were put
in to ensure that if a pin retainer broke and fell out;
1) The pieces wouldn't get to scratch up the cylinder wall.
2) Maybe these are the pin retainers?!
Regards,
Chad Jester
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Jester.c.c%wec@dialcom.tymnet.com |
'74 TR-6 (4) Bitten by the british car bug BAD. |
305/797-1544 (7-5 m-f) |
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From: INTERMAIL-BT (TUMS) Delivered: Fri 21-July-95 11:07 EDT Sys 31000
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Subject: Mail from: <triumphs-owner(a)triumph.cs.utah.edu>
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From: Andrew Mace <amace@unix2.nysed.gov>
Subject: "No more 'ring around the piston' "?
Disclose-Recipients: TRUE
OK, fellow Stanpart Scions, especially you who revel in the hallowed
traditions of Triumph motorsport, this one has me stumped.
Background:
1964 Spitfire 4, built, as best we can tell, as an SCCA-legal GP race car
from a very low mileage wreck (or two), probably in the late 1960s. The car,
in most respects, appears to be a "textbook" example of the original
"Competition Preparation Manual" and practically screams of "V" part
numbers. ;-)
Recently, I brought the car to my house to try to find the problem that has
led most notably to greatly increased fumes, primarily from the crankcase.
Having sat for over two years, the car nonetheless started almost
immediately. And, given the confines of a small, circular, dirt driveway, the
engine felt as strong as ever. (BTW, it is the 1147.)
A compression test, though, told a different story. Readings from cylinders
1-4 were approximately as follows: 158/0/162/160. A repeat test yielded
identical results. A squirt of motor oil and a recheck of #2 yielded a 120
reading. OK, rings are shot; that would explain everything. I'll deal with
that.
Last night, I finally finished getting the head and sump off and the #2
piston out of the block. (BTW, bearings, standard size mind you, still looked
almost new, as did the journal.) As the piston came out through the top of
the block, I immediately saw the cracks in the top piston ring, which fell to
pieces as I finished removing the piston. All else looked quite good, though:
piston looked clean, no scuffing, oil ring looked good, the top two ring
grooves looked pretty clean.
Only one thing was strange: I have yet to find any evidence of the middle
ring! And this brings me to my only real question at this point. Does anyone
have any good ideas as to 1. where the middle ring went or 2. why it would
not have been used when the engine was last assembled (long before we got the
car)? I've never claimed to know EVERYTHING about Triumphs, but...
AM I MISSING SOMETHING HERE?
There's nothing in the sump, there's no markings on the piston or cylinder
wall to indicate that the second ring somehow went astray and wreaked havoc
anywhere? Is this some good ol' racer trick, not to use the center ring?
Forgive my naivete, but I'd really have expected all three rings to be
present! Note: I haven't yet pulled the other three pistons; now I'm really
afraid to!
Oh, one other thing. The pistons appear to utilize "floating" wrist pins. The
piston/rod assembly I pulled last night also has some sort of white nylon(?)
"buttons" inserted as caps on each side. Another racing trick? What for? (I
didn't pull the caps off, so I don't know what is behind them.)
Fellow Scions, I humbly ask your advice, speculation, WAGs, learned
treatises, etc.
Andy "at least as baffled as the sump" Mace
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