V8 engine trial fitting

V8 engine trial fitting

Another break from bodywork required today, so I thought I’d have some fun with the V8 to give me some much-needed motivation. I’ve spent months stockpiling parts for the engine build, but so far haven’t actually checked that everything fits together correctly. On the bodywork side of things I’m also getting dangerously close to turning my attention to the front of the car and the engine bay, so I wanted to trial fit the engine and gearbox in position to validate the exact modifications I will need to make to the shell for it all to fit correctly.

First off I loosely bolted the refurbished sump, front cover, crank pulley and a new water pump into position. This is definitely not the start of the final engine build yet, but getting these parts into place makes for an accurate mock-up of the eventual size of the unit for positioning purposes. This will all be getting taken apart again later, not least because I now have a lovely new pair of stage one cylinder heads and other goodies to fit at some point, but that’s a story for another day!

At the other end, I bolted the shortened remote gear lever assembly to the R380 gearbox, which in turn was bolted to the very nice used SD1 bellhousing I had found, and then I attached the whole lot to the engine. There is no flywheel or clutch fitted yet, again it’s just pretend for now.

With that all put together I hoisted it straight into the engine bay to see how it fitted. It sat quite happily on the engine mounts without much persuasion needed, and it looked magnificent to me, even if it’s only make believe for now. You can see in the main picture at the top of this post however that I have run into one of the common issues with this conversion, the crankshaft pulley is sitting right on top of the front anti-roll bar, so I’m going to need to fix that clearance problem. The “simple” solution is apparently to fit an MG RV8 spec anti-roll bar, which is cranked in the middle and provides a few centimetres of additional clearance, but trying to find one is so far proving a problem, so I may need to engineer an alternative somehow. (Update: turns out that I completely missed in my research that the crankshaft nose on the 4.6 engine is 20mm longer than on the earlier generation V8s, so even though I have the correct GT V8 crank pulley, it’s sitting even closer to the ARB than it should be! I’m going get my local machine shop to take a look at shortening the crank nose, since as well as this issue I will also have problems later on with fan belt alignment with this crankshaft length.)

The next area which will need addressing is the transmission tunnel. The R380 gearbox (and the LT77 which preceeded it) are taller than the standard MGB box, so require extra height to be created at the front of the transmission tunnel before they will fit. I did already know this, but wanted to verify the exact adjustments needed with the gearbox in place before I start removing any metal. The picture below shows the gearbox in the unmodified tunnel – the front of the box is in contact with the top of the tunnel, which causes the back to be pushed down, making it impossible to connect the propshaft. The standard solution to this is to cut a wide channel into the front of the tunnel, and fabricate a new wedge-shaped cover which incorporates a few centimetres of extra height, so that’s a fun job to look forward to.

This picture also illustrates another challenge with this conversion: the mounting holes in the chassis rails for the standard MGB gearbox crossmember are too far forwards to align with the mounting points on the R380 box (which are in the black bracket to the right of the jack in the picture). A common solution to this one seems to be to drill new mounting holes in the chassis rails in the correct position, and then cut holes from inside the car in the floorpans above to weld in new captive nuts. Seems like a pretty invasive job though, particularly when the floorpans in my car were almost literally the only “good” panels I started with, so depending on how far away things are once I’ve made the tunnel modification I may look at trying to modify the crossmember itself instead.

Whilst I had the engine in situ, I took the opportunity to “unbox” the gorgeous new stainless exhaust manifolds I’ve picked up. These are “RV8 style” manifolds rather than the original factory “block hugger” type, so will eventually exit through holes in the inner wings, which I will also need to make before final fitment, so this was just another exercise in familiarising myself with the components.

With all of these things checked I now have a very healthy list of jobs to work through before it will be worthwhile doing another trial fitting. In addition to those mentioned I still have to remove the old radiator mounts and weld in the new V8 spec ones (which sit a few inches further forward for additional clearance), and also weld in the bracket for the V8 remote oil filter just behind the right hand radiator mount. There are also a few localised welding repairs required to the inner wings and around the engine bay that I’ll take care of before I strip it completely and prepare it for painting.

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