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Yes, we’re still skipping over a lot.

So the cylinder heads came back from the specialist, and they looked great. The springs and seats and seals and ports and the rest, all good to go. The surface of the block was fine, so after minor cleanup we fitted the copper gaskets and torqued down the high-strength head bolts.

Assembly lube went on all the valvetrain bits, from the Lunati cam to the Crower roller lifters to the fancy Comp pushrods to the Jessel rockers. We set the valve lash following our previous method, and diligently checked again after some full cam rotations. We double-double checked the clearance on the numbers 4 and 6 cylinders that’d had the problems, but all was pleasingly consistent and boring. 

Intake manifold, on.

This seems like a great time to do a compression check; before the throttle body goes on.

Well that’s sub-optimal.

Then we asked ourselves…

What if the loose pushrods on 4 & 6 during our initial running prevented those two cylinders from experiencing ‘strong combustion’?  They were certainly colder than the rest of the cylinders, that’s how we first found the problem. What if running the motor had a positive effect on the compression of the cylinders that experienced combustion? Perhaps the gas ports in the heads of the piston, in concert with the heat of burning fuel and the shock of the high compression ignition, acted to free up piston rings just in those cylinders that actually ran?   

Hypothesis: running the motor with good-functioning cylinders 4 & 6 will improve the compression measurements in those cylinders.

Our cunning plan

We’ll test this hypothesis by continuing to assemble the motor to get it to the point where we can again start it; then we’ll fire it up, doing our normal checks on temperatures and pressures, and let cylinders 4 and 6 “warm up” and burn some gasoline.

Yes, we’re skipping over a lot.

One of our explorations involved seeing if the motor could start.

Because the car had been sitting for some years, we took pains to drench all of the moving motor parts with oil first. After a few tentative motor rotations, done without spark plugs in, we set the valve clearance on all eight cylinders.

That mundane task gave us more insight into the nature of this beast. The radical roller lifter cam, acting through a set of 1.7:1  ratio rocker arms, produced prodigious valve lift: on the order of .77 inches at the valve. The springs are quite stiff, and the whole valvetrain is under tremendous forces. Finding the base circle of the cam lobs to be able to set lash was tricky; the high lift cam is also a long duration cam. And because there’s no easy way to crank the motor over with a wrench by hand, we were rotating the crankshaft by bumping the starter.

Having set all the valves, we put in fresh gas and coaxed the engine into life. Even with our auxiliary mufflers plugged into the headers, it was horrendously loud. During the initial running, we did determine that two cylinders on the right hand bank were colder than the rest and we shut it off to determine why. Under the valve cover … a mystery.  Both the intake and exhaust rockers for cylinders four and six were loose—free of their pushrods, which were accordingly bouncing around free. The ends of the four pushrods were mushed up pretty badly, as they’d been hitting the rocker arm adjustment cups. 

All the other rockers on both banks were fine. But those four rockers in the center of the right bank were all loose, and all the related pushrods were damaged.  There followed a considerable amount of self-doubt and process-doubt and theorizing and … to no avail: we never reached a satisfactory conclusion of the inquiry, and never reached understanding of the cause.

But everything we’d removed in the quest was overhauled to a high standard before it went back on. The pushrods were replaced en masse with thicker-walled units with more relief (a.k.a. “layback”) around their ball ends. The new pushrods look to have more tolerance for the extreme lift in the valvetrain and its accompanying rocker arm geometry.

 

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While the Flying Pickle drivetrain is re-examined and re-fitted and re-inforced, we’ve acquired a new (to us) land speed racing car. This is a late 70’s Buick Skyhawk, a first cousin to the Chevy Monza with which more people are familiar.  The Skyhawk has a small-block Chevy engine, hooked to a four-speed manual transmission and a Dana rear end. It all sounds so regular compared to the SAAB.

But stand by. The more you look at the car, the more unusual it seems. For instance, under the hood, the valve cover and intake manifold shapes look nothing like a normal small-block Chevy. They also don’t look like a factory Buick V8. In fact… wth is this thing?

To answer that, we must mention the Grand National; this mid-Eighties muscle car used a Buick V6 engine with a performance-oriented cylinder head design. The intake and exhaust runners were all identically shaped, and identically located vis-a-vis their respective intake and exhaust valves, very unlike the standard cylinder heads that GM was producing across its V8 engine families.

Some innovated racers hatched a plan to build a set of “Buick V6 style” style heads for Chevrolet V8s, and thus the “Dart Buick Heads” were born.  Used only for racing, the heads allowed much greater airflow and combustion chamber flame spread than existing Chevy heads and so had a moment in the sun – but sanctioning body rules put a stop to the fun pretty quickly, and relegated Dart-headed small blocks to niche classes in drag racing and circle track.

Eventually the Gen III Chevrolet motors (the “LS” style) arrived with Buick V6 style port layouts, and the LS motors now dominate hod rodding.

So this Skyhawk is a bit of an anachronism – but a pretty cool bit. The motor has the most extreme valve lift and duration that we’ve ever encountered, and an 8650 rpm redline to boot. It’s said to have “at least” 14:1 compression. And aside from whisperings and rumors, we know almost nothing more about it, so our first tasks are investigation and research.

 

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