Requiem for a Small Block

The end came quickly and unexpectedly, with a sickly-sweet puff of burning
Mobil 1 hitting my nostrils a few seconds before the hoarse death rattle hit
my ears. And though I wanted to hope for the best as my '71 Mach I rolled to
a stop, I knew in my gut that the car wouldn't be moving under it's own
power again any time soon.

Up until that point my weekend at Road Atlanta had gone perfectly. The new
steering rack and coil-over front suspension from Total Control Products was
making the car handle incredibly well. With the stock steering gear, you
moved the wheel and after some monkey motion you would eventually feel the
front end begin to move. Now, a flick of the wheel and the car changed
headings like an F-16. My first few laps in practice were my best ever at
Road Atlanta. After seven years of racing the car, I was finally back to
being motor-limited rather than chassis-limited.

In practice, I usually start out following someone as I try to get my rhythm
down and learn or re-learn the track. This time, I was running with a '70
Firebird and a '67 Camaro, both 302-powered Trans Am cars. The Firebird was
an old and quick nemesis from two summers ago at Watkins Glen, but I was
having no trouble staying with him this weekend.

Even my repair of the stripped head stud from the race a few weeks earlier
at Roebling Road in Savannah, Ga., was holding. I'd tried a heli-coil, which
wouldn't take. An insert was marginal, too. Finally, I drilled a hole
through the block 90 degrees to the stud and inserted an aircraft-grade
7/16ths bolt through it to pin it in place. A good squirt of epoxy sealed
everything up.
Needless to say, that was a non-standard repair, and if I'd been paying
closer attention it should have tipped me off that the block was getting
tired.

A dozen laps into the Friday morning practice, I was coming out of Turn 7, a
downhill right-hander. In third gear, accelerating uphill to the bridge with
the motor right at 8000 rpm, I got that first whiff of synthetic oil smoke.
Nothing else smells like it, that simultaneously sweet and putrid aroma, and
it was strong.

The just a little bit and then a cloud of oil smoke came
through the car. I immediately looked at my oil pressure gauge and could see I still had 60 psi. of pressure. Maybe things weren't catastrophic after all. But then the car shuddered harder, and I could see the Firebird start  to quickly recede into the distance.

I flipped the kill switches to try and save whatever was left, coasted off into the grass and pulled it in behind the wall. After climbing out and looking underneath the car, I could see Mobil 1 gushing out of holes on both
sides of the pan. The smoke had come from the oil hitting the Dr.Gas X-pipe just past the headers. car shuddered 

One of the holes was perfectly round and the same size as a rod bolt. It
looked like a snake had bitten the pan, with a pair of holes on each side
right at the 5-6 journal. For the second race in a row, my weekend was over
early. I watched the rest of the practice from the side of the track, took
the tow back to the pits and put the car on the trailer to go home.

The long drive back to Hilton Head gave me plenty of time to ponder the
irony of my engine dying at the same track that had given it birth. In 1994,
I had found out in my first vintage race at Road Atlanta just how much more
horsepower it would take to be competitive against former Trans Am series
cars. It would take a lot more than I had then, well over 400, I was
convinced.

Working with the engineer for Connie Kalitta's drag racing team and NASCAR
engine builder Jim Allen of Morristown, Tenn., we concentrated on making
horsepower with flow work and a good solid top end.

I started with a block I found for $100 in a Tennessee wrecking yard, a
Mexican-made piece from a 1971 Ford pickup with thicker webbing of the main
journal and sidewalls. Not a Boss block by any means, but stronger than a
standard unit at a fraction of the cost. (Despite the folklore that the
Mexican blocks are made of a stronger, higher nickel-content cast iron, I
was told by Ford Motorsports engineer Rod Kack that they're made of the same
metal as American or Canadian blocks, just more of it in some useful
places.)

The block got Boss-style screw-in freeze plugs and a lot of polishing of the
oil parts and opening up of the galleys. A '69 Boss crank, Keith Black
hypereutetic pistons, and timing components from Comp Cams completed the
bottom end. Small chamber Dart Windsor heads were cut down to 54cc volume,
and with pop-up pistons the compression ration was almost exactly 13.0:1.
Rotating parts were externally balanced with the flywheel, clutch and
pressure plate on the engine.

 

On the dyno, it made 530 horsepower and 475 ft/lbs. of torque and was so
strong and reliable that I was able to race for almost five years without
needing any major work.

I'd hoped it was just a rebuild I'd be needing when I got the car home.
Sunday, which would have been race day, I dropped the oil pan with the
engine still in the car. The first thing I could see as I removed the pan
was the broken timing chain, hanging down. As the pan moved around, it
sounded like a slot machine paying off $50 in quarters and felt very heavy.
The outside looked like someone had hammered a bag of marbles into it. Not
good, not good at all.

Once the pan was out, I could see a wrist pin lying in it, along with half a rod broken and twisted, the small end beaten flat. Everything looked burnt. There were lots of pieces of moly ring, and a blizzard of pieces of piston the size of my thumbnail. The windage tray was shredded. The stud girdle at the 5-6 journal, made of
laser-cut 4130 chrome-moly steel, was bent into a U-shape that looked like Superman had been battling criminals somewhere inside my engine. I could look up from below and see four camshafts, which is also not usual and not good.



A few days later, I pulled the engine and began tearing it down on the stand. The camshaft was broken into four pieces.  Timing gears were still intact, but a lifter was sheared in half. The No. 7 piston, I couldn't get out of the block. It jammed itself past the bore, almost on top of the crankshaft, and wouldn't come out. The crank itself was in good shape, and the ARP studs all held even as the rest of the engine came apart. The block was cracked and broken in multiple places, although I noted with grim satisfaction that my pinned head stud repair was intact. My belief after looking at the motor and talking with Ford Motorsports, is that a rod bolt failed on No. 5. It sheared off at the nut, shot into and through the pan causing the initial puff of oil I smelled; the big end on the rod let go and it was showtime at the Apollo after that

.On a two-bolt-main block, making over 500 hp is a recipe for an engine failure because the block flexes and eventually crumbles. The key word is eventually; 150 hours of road racing across several years in my case. SVO has post-mortemed a lot of small blocks, and has seen these failures enough times to know both the causes and the solutions to them. Since it looks like I'll be starting over with a new engine, I'll have a chance to think about what I need from the perspective of several years of experience with the car. A four-bolt-main block maybe in the cards, and I'll want the finished motor to spin to 8000 rpm, make 600 to 700 hp and 500-plus ft/lbs. torque, and do it with a compression ratio of no more than 12.5 - 12.9:1 or so. Will it live as long as the last, lower-output engine did? I hope so. Vintage racing on a budget is a series of gut-wrenching tradeoffs between making things last as long as possible and going fast enough to be competitive. Using higher-quality parts should let me balance the output I need with a reasonable life expectancy. Maybe start with a SVO aluminum 302 block, with Victor Jr. or GT-40x heads. A 347 stroker or a 351, would be a nice addition, as would a Comp roller cam, push rods and lifters. If this were November and not mid-May, I could spend a leisurely winter getting parts and doing the build-up. But missing the rest of the racing season is distinctly unappealing, so I have to reconcile my wants with what will get the Mustang back on the track as quickly as possible. Making the Watkins Glen event on June 1 is all but impossible, but mid-July at Danville, Va., might just be doable. I won't know until I try.