DIRTY STUFF

IWORK on many high-performance engines, most of them heavily modified, and I’m often amazed to find major stuff-ups by previous engine builders who really should’ve known that you must be meticulous in the way you bolt a mill together, right down to the most insignificant things. I just had a case with an older race engine (the ’plugs fired by conventional coil-and-distributor ignition) that still has me gobsmacked as to how the original engine shop overlooked a small but absolutely vital component and totally ruined the owner’s past two years of competition.

He would turn up at race meetings with his car, which should have been really competitive in its class, only to run around at the back of the pack until all the onlookers assumed it was his driving ability that made him so slow. The poor guy couldn’t understand why he wasn’t up there with the hotshots at the front of the field.

I got his engine to repair after it broke a cam follower foot while the original builder was overseas on a long holiday.

Before I tear down any engine, I always fit a degree wheel to the crank and use a dial indicator set to check both the valve timing and the ignition timing so that I have a grasp of how that engine was set up.

The ignition was set at the usual 18 degrees static, the valve timing was as expected with a full-race Cosworth cam, but when I tried to manually check the amount of centrifugal advance in the Lucas distributor, I couldn’t get any movement when I tried to turn the rotor.

With these distributors, it’s quite common for the cam to rust inside and seize on the shaft. This car hadn’t turned a wheel since the engine died eight months earlier, so I lifted the cap, found a ring of rust and figured that was why this cam didn’t move.

Didn’t think any more of that and went on to pull the engine down into small pieces, finding a stuffed cam lobe and exhaust valves made from sil-chrome instead of stainless or austenitic steel, so the guy was lucky that not one exhaust valve head had dropped off and smashed into a piston.

Mostly, it was all good bits inside this mill: billet steel crank, forged conrods and pistons, steel main bearing caps, billet steel flywheel and an uprated chain-drive to the camshaft to cope with heavier valve spring loads. Even the cylinder head shaping and porting were about as good as you can get with a stock casting.

But when I lifted the point plate out of the distributor, intending to unseize the cam and see how many degrees of advance that would allow, I looked into the bowels where the double weights and springs live, and damn near dropped my screwdriver in total astonishment. Some nong had got to the base of that cam with an oxy welder, right where these Lucas parts have a flat metal dogleg specifically to limit the amount of turn that the cam can make and thus control the degrees of available centrifugal advance. Lucas even stamps a number on that leg – anywhere from 10 to 18 degrees – so you know what you’ve got in the spring-controlled space between the end of the leg and an upright pin welded into the bottom weight plate.

But for some idiotic reason, this nong had welded a piece of steel onto the end of the leg, locking the centrifugal advance facility solid – and that’s why the cam wouldn’t turn!

How do you miss something like that? Apparently, when this engine was being built, the owner had a distributor modified by an auto electrician specifically for the engine. But the builder wasn’t too fussed when he saw it. He said he had a better unit and he fitted that instead, not realising or checking that this had zilch centrifugal advance. He set the static at 18 degrees, the engine was dropped back into this race car and was never tested on a chassis dyno.

So for two years, the owner was racing with really retarded ignition timing, not knowing that he was getting less than half the power his engine should have been producing! No wonder he was struggling at the back of the field.

WHEN I TRIED TO CHECK THE AMOUNT OF CENTRIFUGAL ADVANCE IN THE LUCAS DISTRIBUTOR, I COULDN’T GET ANY MOVEMENT. IT’S QUITE COMMON FOR THE CAM TO RUST INSIDE AND SEIZE ON THE SHAFT

At least I was able to fix the problem. I know a guy who was an auto-electrical rep for many years and he used to buy up old Lucas stock wherever he went, so now he has a large shed filled with catalogued NOS parts, from starter motors through lights and fittings to distributors and their pieces.

He located a brand new 12-degree cam that fitted my distributor, and as the dizzy shaft only rotates at half engine speed, that distributor works out at 24 degrees crankshaft. So with the static ignition timing set by my crank-mounted degree wheel at 18 degrees, we had a total of 42 degrees all up – about right for these engines.

Wrong ignition timing in any engine will always lose teams of horses, so with this stuff-up fixed, the driver is going to need lots of brave pills!