Street Machine - - Dirty Stuff - WIL­LIAM PORKER

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 high­vol­ume 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.


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