RIGHT, now I’m a believer. My sainted mother often said that bad things happen in threes. And after this disastrous chassis dyno session involving a totally rebuilt HJ Monaro – mate, I reckon I’ll be seeing bunyips next!
It went like this. Got a ring from a guy who wanted to hand over cash money if I would sit in on his dyno test session. Over a couple of years, he had torn apart his HJ two-door, right down to the bare metal, and finished the ground-up resurrection. Left Holden’s 308 V8 in situ, revived with an overbore and stroker crank, sucking through a fat Holley into Yella Terra heads, valves lifted by a savage hydraulic cam and running modified Bosch ignition, out back was a brass button-clutch driving a Tremec five-slot ’box, the thickwall driveshaft coupled to the original rear axle.
So we all met Sunday arvo at the dyno shop, ’cos weekday-working neighbours get upset during noisy damn dyno runs and often threaten violence to the testing crew. So we set the Munro up on rollers, then lit the fuse. That initial run proved his worked 308 had bugger-all grunt, and refused to run over 5000rpm. Not unexpected, as the cause for this could be a lean or rich fuel/air mix, weak valve springs, dead-wrong ignition timing or inadequate fuel flow. He had fitted a Holley Blue, so that should be okay. The valve springs were new and rated at 340lb fully open, and the initial exhaust gas sample was on the high end of 14. And the bloke who owned this machine said the Bosch dizzy had been set up by the expert, dead-right for his Oz V8.
So I grabbed a strobe light, running the engine to see the timing marks, lifting the revs to check that the marks were actually separating, and they weren’t. Bloody seized centrifugal advance mechanism inside the distributor. So I ripped the unit out of the engine and into small pieces on a work bench. The ‘expert’ sure had been busy, ’cos he had fitted new weight springs that were so strong they effectively stopped the distributor from advancing. So the spark was on full retard.
I fixed that by bolting in another stock distributor, and got serious grunt – until we suddenly had a fierce fuel fire inside the engine bay. By the time somebody got to an extinguisher, a lot of new paint had blistered, the plug leads were stuffed and the Holley was looking real second-hand.
With the heat and fury shut down and the owner sedated with a large dose of Valium, we gave the bay a quick clean and replaced the burnt bits. Turned out, the cause of this disaster was a ruptured braided fuel line feeding the four-hole carb – a brand new piece that had suddenly let go at the union. That was another quick fix, and then we got ready for a final run, as the shop was about to throw us out and lock all the doors. We should have quit right there. In fourth gear at 6800rpm, there was one hell of a bang-crash noise from underneath. Sparks flew everywhere as the car tried to leap into the air against the holding chains, with a sudden stench of burnt oil and yelling from the terrified testing bloke behind the wheel. Then silence and smoke, and a piece of bent pipe hanging out from just ahead of the right rear wheel.
That was the tailshaft, which had sheared at the front universal joint. And with no safety strap fitted to contain the shaft in case this happened, the damn thing had flailed around everywhere, broke the rear of the gearbox, stuffed exhaust pipes, and badly bent the floorpan. The dyno was damaged, the poor car owner is still weeping, and I’m still looking for bad-luck bunyips!
One engine problem that rarely gets a mention is oil retention in high-revving mills. As you cannot see what is happening inside a sump when the crank assembly is spinning at warp speed, it’s difficult to imagine that a huge amount of vital lubricating oil has been trapped and is spinning around with the crank and conrod assembly. With a high-volume pump working, as much as two litres of oil gets wrapped up, and this takes away horsepower. Smart engine builders fit crank scrapers and windage trays that physically scrape off a lot of the trapped oil and returns it to the sump well.
And when we modify pushrod OHV engines, that often causes yet another oil problem. With big-lift cams and super-strong valve springs, stock pushrods are then too weak and bend, altering the valve timing. So we fit fatter chromemoly pushrods through the same small holes, totally forgetting they share this same space with oil trying to get back to the sump. So this oil – as much two litres in a V8 – is trapped inside the rocker boxes. And in extreme cases, between the oil wrapped around the crank assembly, plus more upstairs. You will either suffer oil surge or run out of the stuff real sudden-like. And at upwards of 7000 rpm, your expensive engine has only a few seconds left to live.