Triumph TR6
Matt gets his TR’S engine machined by the experts
After a successful engine tear-down session at TRGB (PC, Spring 2018), the next stop on my journey of engineering enlightenment was Ivor Searle Ltd in Soham – you can find about more about the company itself in Marketplace (p78). The TR’S engine block, crankshaft and con-rods were all in need of machining, while the camshaft I’d earmarked for the build was also brought along for a once-over by the experts. Guiding me through the process was Trevor Gilbey, who has worked at Ivor Searle for 42 years – cliché it may be, but after so many years on the job it is safe to say that what Trevor doesn’t know about machining really isn’t worth knowing.
With Trevor as my guide I was able to follow my components as they made their way through the system. After being chemically cleaned and derusted, the crankshaft was ready for a grind. Technician Andrew Quinn carefully set it up on the grinding machine and set to work. My crank only needed minor remedial work and was ground down to first undersize, the result of which being that I’ll only need to use +10thou main bearings during the rebuild process. The crank journals were then lapped and polished.the engine block itself was also chemically cleaned in order to remove any corrosion from the exterior and expunge the build-up of scale and corrosion in the internal waterways. The boring process was anything but boring and, again, my block only required taking out to first oversize. This means that +20 pistons will be be used for the engine build. The con-rods were also checked for straightness, then balanced and fitted with fresh little end bearings. So far, so good.
Smooth operator
Each piston bore in the block was then honed – honing is an abrasive machining process that produces a precision surface on a metal workpiece by scrubbing an abrasive stone against it along a controlled path. Honing is primarily used to improve the geometric form of a surface, but may also improve the surface texture and the honing device itself consists of one or more abrasive stones that are held under pressure against the surface they’re working on.
In the context of an engine, a smooth glazed cylinder wall (the result of the boring process) can cause piston ring and cylinder scuffing, so a ‘cross-hatch’ pattern is employed during the
honing process. The pattern allows for the retention of oil to ensure proper lubrication and ring seal of the pistons in the cylinders. Once the honing process was complete the gasket surface was refaced and the recesses were cut to the correct depth, then the block was finished.
Lastly, Searle’s fitted new little end bearings into the TR’S con-rods. Once all the components are back at TRGB the con-rods and pistons will be weighed and matched up accordingly. After the heavy-duty nature of the machine works, I can’t wait to get stuck into the engine build proper.
Cut and paste
Away from the mechanical works, there has also been progress on the body front. After painting the passenger side inner wing/engine bay last month, Matt Tomkins and I shifted our attention to the driver’s side inner wing. Something clearly wasn’t right there as the wing on that side of the car was very much not lining up with the front valance. A further inspection revealed that the issue was being caused by a less than perfect period repair to the inner wing/wheelarch. The car had obviously suffered a bump on that side at some point in the distant past (the aftermarket wing in red primer was also a bit of a giveaway) and the internal panel had been squeezed back an inch or so. To compound the issue, the inner wing had simply been ‘repaired’ with a series of blobs of brazed flux. The results were scruffy and, most problematically, also prevented the external wing from lining up correctly.
The only way to remedy the issue was to cut the inner wing away from the inner wheelarch and weld it back together in the right position… it doesn’t sound that scary when you say it quickly! After I’d cut the inner panel away by carefully running a slimline cutting disc through the brazed joints and between the two panels, we bolted the wing to the internal structure and set about pushing, pulling and generally teasing everything into alignment. Various hammers and dollies came in handy and, after a few hours, we’d got the alignment between the front valance and the leading edge of the wing into shape.
With the wing bolted along the top, bottom and front, it didn’t take Tomkins long to weld the inner wing and wheelarch back together. As ever, it was the preparation work that took up the majority of the time, with the welding torch then getting its work done in a matter of minutes. Once the wing welding had been completed. and with the passenger side of the underbonnet area already resplendent in fresh paint, the driver’s side could now be addressed. I’m writing this on the Monday after the
Practical Classics Classic Car and Restoration Show at the NEC, so if you came along to the show then hopefully you saw the results for yourself. It was a great weekend of TR progress on the PC stand, so I’ll report on that soon.
matt.george@practicalclassics.co.uk
‘Cutting the inner wing away – not scary when you say it quickly!’