Working on half-cuts

Posted on June 5th, 2005 in Opinion by Julian Edgar

A while ago we covered the costs and benefits of buying a half-cut versus just a bare engine, loom and ECU (see Buying a Half-Cut). In short, the positives of a half-cut are huge – sure, you pay more, but you get the gearbox, front suspension, gearbox, dashboard, ECUs and so on. But as I said in that article, man-handling a half-cut around is a much bigger ask than doing the same for just an engine. In a front-wheel drive, a half-cut may well weigh 60 per cent of the mass of the entire car – so even with what today is a fairly small car, three-quarters of a tonne.

Click for larger image

Most often, the half-cut is bought for an engine transplant – one modification that has major benefits when taken via the half-cut route. Not only do you get all those ECUs and looms, you also get the instrument panel and the radiators. But irrespective of whether you’re buying a half-cut for an engine transplant or simply as a spare driveline, inevitably you’ll have to get the mechanical bits out of the body shell.

I’ve done it a few times over the years – with an R31 Skyline half-cut from which I took the RB20DET six cylinder turbo engine and RWD gearbox, and more recently, from a first generation FWD Toyota Prius hybrid. In fact, it was only a few hours ago that I was working on the Prius half-cut. In each case I removed the engine and trans in much the same way.

But what’s the problem, you’re asking? What’s the big deal of removing an engine or an engine/gearbox combination from a car? After all, all you do is undo the engine and/or gearbox mounts, disconnect the wiring loom, radiators, driveshaft(s) and steering shaft – then lift the bugger straight out. But doing it that way gets a bit harder when you have only half a car. And no forklift. For starters, the half-cut is only going to be supported on bricks or jack-stands – no where near as secure as a car sitting on its wheels, or a car with its rear wheels on the ground and its front on jack-stands. Secondly, separating the driveline from the rest of the mechanicals in this way is quite likely to be a retrograde step, causing you to waste time later on extracting the other bits that you want.

Nope, I do it differently. (And I am sure that plenty of others do it the same way – it’s just that I never see it mentioned.) What I do is to reverse what the factory does.

Click for larger image If you ever go to a car factory, inevitably you’ll see a car assembled in much the same way. After the body has been near completed, it’s mated with the mechanicals that have also been completed. Irrespective of whether it’s a front-wheel or rear-wheel drive car, the body is lowered over the engine and front-suspension, the latter normally bolted to a sub-frame that also supports the engine. In the case of a front-wheel drive, the front mechanicals consist of not only the engine and gearbox, but also the driveshafts. (In this Volkswagen Phaeton assembly, you can see the complete driveline is installed at the one time!)

To work the opposite trick with a half cut, you can start with it sitting nearly on the ground. In fact, it needs to be elevated by only 100mm or so – just enough room to get a spanner underneath to loosen and then remove the subframe bolts. The upper front damper (or strut) bolts are undone, the radiator hoses removed and the wiring loom plugs all unclipped. The steering column is disconnected (often easier when you’ve already started the next step) and the other bits and pieces that I always forget – like the heater hoses and air con lines – are separated.

Then – and here’s the key step – the body is lifted up over the engine.

It’s pretty hard to do that when you’re working with a full car body, but when you only have the front half, it becomes a lot easier. If you have a four or so hefty blokes around the place, the body can be physically lifted up over the engine/gearbox/subframe/driveshafts/suspension assembly and placed to one side. In my case, where I was working alone, I used an engine crane to lift the front of the half-cut shell up over the mechanicals beneath. Once you get the half body shell tilted high enough, it can either be rolled over onto its back, or propped in the ‘up’ position and the same engine crane used to lift the mechanical assembly so that it can be wheeled away. (Obviously be really careful that the body shell is supported in such a way that it cannot collapse on you when you’re shifting the mechanicals out from under it.)

Click for larger image In this way, using just an engine crane (and in the past I did it with just a hydraulic trolley jack and lots of timber blocks) allows you to easily extract pretty well all the mechanical bits of interest in just one operation. In the case of the Prius, which has a very tight engine bay, the driveline can only be removed from underneath, but irrespective of the car, it’s a quick and easy method. In fact, while this morning I wrote on my list of today’s things to do ‘remove Prius driveline’, I expected it to take at least a few days of solo effort. But to reach the stage shown here took only about 4 hours.

For a slow worker like me, that’s quick!

Comments are closed.