->
->Connecting rod bolts are what we're discussing here. I've ordered
->new ones in spite of having been told that the old ones should be
->reusable (they're specially hardened, or so I was told), and we
->were discussing ways of keeping them from loosening up in the caps.
->The general consensus seems to be to dump the tab washers and go
->with a better solution such as safety wire or Belleville washers.
->
->~ If you want to go with safety wire, I've got a safety wire drilling
->~ jig which makes it a snap.
->
->Thanks, but I've already lined one up. I don't know whether it will
->really buy me anything other than the warm feeling I will get motoring
->down the road knowing that I safety-wired the rod bolts in my motor,
->but maybe that's worth something. :-)
->
I stopped in at the machine shop that has my Spit engine last night.
They've got all the machine work done save drilling one hole in the
block. ( a whole 'nuther story...) While I was there, I got talking to
the guys who build motors. These folks build nationally competitive
drag and circle track motors. We got looking at my con rods and talking
about building motors. I had brought them 10 con rods in the hope that
we'd be able to get 4 that matched and were not cracked, a known
problem with racing Spit motors. They got exactly 4, might have been 6
except for the fact that 2 were rebushed at the top end already, and
they didn't like that idea for a motor they thought might see 7000
rpm...There were a few other tweaks that they made as well.
We talked about the failure mode of the previous 2 engines, an apparent
oil starvation problem, leading to con rod failure. The conclusion of
well over 70 years of building fast motors was that they had never seen
a con rod bolt fail. Bearings due to lack of clearance, the very
occasional rod failure due to a pre-exising crack not found due to
someone being cheap and not magnafluxing the rods. (Really easy to
determine btw). The majority of failures was due to bad bearing
clearances which lead to bearing meltdown, which is followed by the
crank smacking back and forth in the big end, which is followed very
shortly by either the rod cap or rod bolts failing. But they all said
rod bolts get blamed alot because it's easier to blame a bolt for
failing than it is to blame one's self or partners for getting bearing
clearances wrong....
Given the current dillemma, I asked about tab washers, etc, and they
said the same thing that Carrol Smith said, if the washer is going to
deform under the 40-60 ftlb load of torquing, what is it going to do
under the 4000G loading of a race engine @ 6000 rpm? (Note, F1 engines
are 8000-9000G's at the piston...) Torque it to the right specs, use
loctite if needbe (but only the right stuff) and move on to other
engine parts. And as far as safety wire goes, the concensus was "You spend
bunches of time getting the rods lightened as far as possible and matched down
to the last 10th of a gram. Whyinthehell are you going to add more weight of
an unknown amount.
About that hole being drilled in the engine...We discovered while
rattling around the garage one night an interesting fact. The standard
Spit spinon oil filter is a 3/8" thread. The other standard oil filter
thread size is 1/2". 1/2" is used in Amurican cars, and more
importantly, Volkswagens. Why are VW's important? Because the garage I
work out of is a VW/Audi shop. I was talking to the proprietor, Lenny,
about my oil cooler being full of debris from the last engine
detonation, and thinking about replacing it. Lenny wondered about
doing an oil/water intercooler and then using the car's cooling system
to handle the rest. I thought about it. The temp Delta (I *want* a
delta key....)isn't as high, but the transfer is much better. After a
minute or two of discussing it, I determined that it was a neat idea
but that it wasn't worth persuing due to the inherent difficulty of
fabbing the intercooler. That's when Lenny said "Fabricate?! Why would
you do that when a perfectly good one is available? If you can't
improvise, we can't use you." He wandered over to a dark corner of the
garage (of which there are many) and out rolls a small aluminium box
about 4"x4"x2.5" with two pipes coming out the side. Instant
intercooler. Stock part for VW Vanagons. We cleaned it up and sure
'nuff, if we change the oil filter fitting from 3/8" to 1/2" it bolts
right up. And conviniently enough, in the race car, there's this pair
of hose fittings where the heater used to go...Stay Tuned.
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