Engine Mounts Started

Well after a night to contemplate my engine mounting choices I made a few decisions

1. The engine will be hard mounted... it is quite a long way from the perimeter of the chassis so I'm hoping it will be OK
2. I'm going to externally bridge across the two mounts on each end of the cylinder head to distribute the loads across them.
3. The front mounts will be triangulated to the existing mounting ears if possible. and the rear gearbox mounts will be fitted to the chassis floor members.
4. The upper gearbox mounts will be connected to the main diff hardware, and I'll stabilise the diff hardware by connecting it to the rear chassis rails, thus stabilising the rear gearbox mounts.
5. If possible I'd like to get the engine in and out easily... which means no inaccessible mountings like the cylinder head fittings on the ZX12r.

So having got it all worked out in my head, I then went into the garage, looked at the engine "in the flesh" and then spent a further 45 minutes umming and aaarhing as I reworked my ideas.

First job was to align the engine height. This was easily achieved as I simply sat it on some 2 inch box section that was positioned on the sheet of blockboad. This positions the sump about 1 inch above the main floor level, but it actually still sits in the airflow as the floor slopes upwards towards the rear. I did this deliberately to get the sump in the airflow as I think I'm going to need the additional oil cooling.

Next I was necessary to align the engine so that the output sprocket points along the longitudinal axis of the car. It took me a while to work out how to do this. But eventually I spotted that the center of each camshaft is marked on the casing. The cams will be definitely be perpendicular to the output shaft so measuring from the bulkhead chassis rails to the centre of the exhaust cam on each side of the engine and ensuring the measurements are identical should align the sprocket correctly

So I spent three or four hours today cutting welding, measuring, drilling and tapping bits of steel. By the end I had ended up with two pieces of the first mount as shown in the picture. The piece that is bolted to the block bridges the engine mounts. It has some standoff sleeves welded into each end to move the mounting away from the engine so that it can clear the water pipe union that you can see just below it. the middle boss is actually tapped M12x1.75 and has sufficient room at the rear for a jam nut to be fitted once the mounting bolt has been wound through it, that way it shouldn't come loose from the vibration. Incidentally this sleeve isn't threaded all the way through, the first 5mm or so is drilled to 12mm clearance to allow the bolt to get a start in the correct alignment. My experience with holes threaded right to the end is that they are a pain to get started, particularly if you trying to align heavy stuff like engines, but with a short section of clearance the job is much easier, having changed an engine in the paddock I'm hoping that little things like this will help a lot should I ever have to do it again. This was another reason for going for the single bolt connection on each side of the cylinder head.

The other section of tube connects to the existing mounting ears on the upper bulkhead chassis rail. The sleeve in the end is not threaded but is accurately drilled to a 12mm bore. Next I'll triangulate the end of this mount down to the mounting ears at visible on the lower chassis rail in the left of the picture. So I've made a start... just this side to finish... the other side to do and the gearbox mounts to get done. Then I can say the engine is mounted.

The threaded bushes and clearance sleeves are all made from 5/8th OD, 12 gauge wall steel tubing. One of the oddities of steel is that it is still mostly sold in imperial measurements. However it is important to buy tube that has smaller a bore than required and then drill it out to the bolt shank size. This will stop the bolts rattling in the tube and hold everything together nice and tightly. I'm using M12 bolts and 5/8th x 12g is a very handy size as its bore is about 10.2mm. This means that it can be perfectly tapped to M12x1.27 without the need to drill a pilot hole and it can of course be drilled out to 12mm for a nice snug sliding fit. Lastly it's OD is almost exactly 16mm which makes it easy to cut mounting holes in the box section tube using as stepped hole cutting bit.