[Wichita-SCCA] Engine Rebuild

[Greg Laws]

Just to back up what Guy said about checking engine oil before coming to a 
solo, failure to keep engine oil level up can be VERY expensive!

Guy's engine had a nice, clean upper end.  That is to say that the cylinder 
heads, valves, camshaft, etc. all were in good-to-excellent condition.  The 
cylinder walls were slick and pretty.  The pistons looked almost new.  So 
far, so good.

The crankshaft had problems.  Connecting rods #5 & #6 (both on the same 
crank journal) had darkened to the point of turning blue.  Bearing material 
was squished out of both rod's big ends and the crank journal was worn down 
& ugly.  In popping the eight pistons out, I noticed that there wasn't much 
drag from the piston rings and also, in pre-teardown testing, the 
compression readings were all over the map.  Okay, we're talking replacement 
crankshaft, replacement of two connecting rods, and then the usual rings, 
bearings, and gaskets.  It could have been a LOT worse.

Lesson to learn:  Checking the oil is just something that you should do --  
every time.  This includes being prepared to bring the level to FULL even if 
it's down only a little bit.  Many experienced autocrossers run a half-quart 
over full just for insurance.  At redline while going through a sweeper, 
most if not all of the oil will be caught up in the top of the engine 
struggling to drain back to the oil pan.  This can leave the oil pump pickup 
high & dry, a situation that most engines can tolerate occaisionally and for 
only very brief moments BUT which which will lead to enivitable failure if 
done too often or for too long a period at one time.  Not to put too fine a 
point on it but Guy's engine failed from oil starvation and no other reason.

Guy would be the first to admit that he tolerated a long-term oil leak 
problem too.  Running an engine low on oil, even in ordinary driving, tends 
to overheat the remaining oil.  The oil turns dark brown and starts to smell 
bad.  It also tends to become gummy with brown varnish.  Such inadequate oil 
may be part of the problem with Guy's cylinder rings losing tension.  The 
rings may be stuck in their grooves by gunk.  I haven't gotten that far in 
the teardown to say for sure yet.  In any case, poor piston ring performance 
allows blowby pressure into the crankcase, thus overpowering every seal & 
gasket allowing engine oil to mist all over everything in the engine 
compartment and to blow back underneath the car.  Oil mist & dirt throughout 
an engine compartment is a sign of a very tired engine heading for failure.

Guy's clutch seemed to be in good condition.  In fact it may have been 
replaced sometime before Guy ever bought the car.  I say that because the 
flywheel surface had worn down well below the original surface of the 
flywheel but the pressure plate & driven disc didn't look that bad.  My 
guess is that the clutch had been replaced but that person did not take the 
much-needed step of resurfacing the flywheel at that time.  Thus the new 
clutch quickly became useless and the clutch diaphragm spring came out so 
far that it refused to release the throwout bearing.  I've never seen a 
clutch do that before.  It flat out refused to release tension enough to 
release the clutch fork even when we had every bolt out out of the 
bellhousing and everything else loose!  There wasn't clearance to allow 
access to the pressure plate mounting bolts so I finally had to grind the 
tabs off of the throwout bearing collar before it would release the fork and 
allow further disassembly.  This all because of excessive wear on the 
flywheel surface.  This regretable grinding operation destroyed the pressure 
plate assembly of course, but at least we were able to get the thing apart.

Lesson to learn:  Replacing the clutch properly includes at least checking 
the flywheel surface for being flat and then having a machine shop mill the 
flywheel surface smooth again if needed.  Slapping a new pressure plate and 
driven disc onto a worn flywheel achieves only more trouble not much further 
down the road.

And so it goes....

Enjoy,
Greg Laws