Boom #8, blown head gasket, melted both poly motor mounts, wounded Opti

Intro  Boom #1  Boom #2  Boom #3  Boom #4  Boom #?  Boom #6  Boom #7  Boom #8  Boom #9  Boom #10

Many of you will recognize these symptoms.  Its starts with the occasional need to top off the coolant.  When that need becomes more frequent, you go into aggressive denial.  Denial becomes more difficult when backing down the driveway after a cold start leaves a trail of black water puddles that stain the concrete.  But when I pulled my y-pipe after a 30 minute drive and poured several ounces of water out of the Mufflex, there was no escaping the fact that I had a blown head gasket.  The pix below show the details.

The driver side pic on the left shows no damage, but the passenger side pic in the middle shows that 2 and 4 took a hit.  In fact, #2 gushed coolant out of the spark plug hole as I turned the engine over for torque converter bolt access.  Note the gasket deformation in the close-up.  Engine builder Mike Blackstone told me he had never seen anything quite like it.  Gee, what an honor.  Also note how clean the piston tops are after just a quick wiping with a shop towel.  This engine had 10,000 street miles and a bunch of strip passes on it.  Mike thinks the cleanliness is a sign of running too lean, so I'm building 2 of the DIY-WB (Do It Yourself Wide Band) O2 sensor circuits that will be used to dial in WOT fueling next time.  But maybe it's just due to the steady diet of Chevron premium.

A couple of other problems surfaced as a result of this rebuild.  The first one was the melted (as in *ruined*!) poly motor mounts.  The passenger side poly, which had started to melt *a little* back at Boom #7 is now flopping around in the clamshell.  The driver side poly, which had only been in there for a few months, was melted so much that the through-bolt hole was way off center.  I was wondering why the engine has developed a bit of a lean.  My application may be a bit extreme, but I've heard stories of other guys melting these things, too.  Not recommended.  I'm going with solid mounts this time.

The next problem came to light as I disassembled my Opti to install a new cap and rotor.  I found the head of a machine screw rattling around under the metal shield.  It looks like it backed out, rubbed against the timing wheel for awhile, then snapped off.  As usual, my attempt to salvage the Opti came to an abrupt end when the EZ-out broke.  Seems like they always do, even when I am very careful applying the torque.  Note how much the head of the machine screw had worn down.  It amazes me that the car ran as heard as it did (9.94!) with this Opti.

After ordering a new Opti (from Chris Slack of Team Chevy this time chriss@teamchev.com), the next step was to enlarge the idle air holes in the intake.  These holes, visible in the port floor, admit air metered by the Idle Air Controller (IAC) into the engine.  In my quest to conquer the dreaded Split Block Learns, I'm trying to get *all* of the idle air to flow through these passages.  Problem is, my engine won't idle with the throttle blades closed even with an IAC of 160 (max open).  My working theory is that the idle air holes leading to the ports may be undersize for the 15+ gps my engine inhales idling at 900.

After tracking down a 9/16" allen wrench (not all that common, it turns out), I pulled the 4 plugs on the bottom of the intake and found what's shown below-left.  7 of the holes were drilled to 15/64", but 1 is only 5/32".  That couldn't have been helping my split BLMs.  The new holes are *all* 9/32", and I cleaned up the inlet ends because, well, because I could.  BTW, I know the holes looked mangled, but hey, I used a cheap cordless drill with a *very* sharp bit.  That bit would catch the soft aluminum and almost pull the drill out of my hand.  I'll let Blackstone handle all the important machining :-).