Tuesday, 31 March 2015

Trials and Tribulations

21 Feb
Yes – up and running – just about! First venture onto the public highway last Sunday. Just a few miles down the A50 to the roundabout and back. No hood yet and it’s really not warm enough to try fitting it – the fabric needs to be stretched when warm – so with temperatures at best just a few degrees above freezing, longer trips can wait. Yesterday drove down to see John Greatorex at Stretton Airfield. I wanted John’s advice about the persistent cammy rattle from the engine. While John was listening to the engine it gradually ran rougher and rougher. On the way home the engine struggled increasingly to produce any power, and finally expired two miles from home. Returned home inauspiciously behind an AA van.
The AA man thought the low tension ignition circuit was suspect, and sure enough replacing the (new!) condenser with one I’d had in storage for 30 years since my Scimitar days brought the engine back to health.
John’s verdict on the engine wasn’t good – he recommends removing the engine and stripping it down. He suspects top or bottom end problems. To me, the rattle seems more camshaft speed than engine speed – but we’ll see. I’m proposing to let John sort it out – I don’t have space to store the car and strip the engine down. John Greatorex is at GT Cars Ltd, Appleton.
Poorer but wiser!
Collected the car today after four weeks in John’s care. The rattle was far more serious than I imagined and has provided a costly lesson. ‘Foreign objects’ had been ingested into cylinders 3 and 8. John found parts of a 5/16” washer in no. 8 combustion chamber, where the damage was worst. The washer had entered the squish area between piston and cylinder head, rattled about and written off both piston and head. On no.8 the piston had been so battered that the top land was rubbing the bore, and had deformed to trap the top ring. The bore was marked.

I had to quickly find a replacement block, heads and two pistons. Fortunately Paul at Abbey Sportscars came to the rescue and shipped the items direct to GT Cars. John and Dan worked on the Rover with the same enthusiasm they show for their ‘regular’ Ferraris, while sparing me the supercar rate! My Ace and its engine now feature prominently on GT Cars facebook page!
The cause in No.8 and probably No.3 was a washer entering the combustion chamber. The most probable explanation was that the washer was unwittingly dropped before fitting the inlet manifold, entered an inlet port and lodged behind the inlet valve. On turning the engine over to set timing, the inlet valve’s opened and deposited the washer onto the piston, where it’s slid over into the squish area.
Lessons learned:
1.       Whenever the inlet manifold’s removed, plug the inlet ports with rag or cover with gaffer tape;
2.       Immediately before re-fitting manifold sweep the inlet ports with one of those little magnets on a telescopic probe; I’ve now demonstrated this quite a few times and it seems to be 100% successful in recovering small washers;
3.       Consider acquiring an endoscope to confirm the inlet ports are clear. This can also give a view of the piston top via the spark plug hole. These are now available very reasonably – I’ve acquired one for £45 and it does work ….
While the engine was being rebuilt I’ve been having silencers made for my own design of exhaust that will run well outboard of the main chassis rails and give more ground clearance. The upper part of the silencers fits close to the floor under the seats, between chassis outriggers. I collected these last week from JT Exhausts of Macclesfield.

I’ve now got a month or so to get some miles under the belt and sort out the exhaust, hood and sidescreens before the Welsh Road Trip in May – let’s hope the weather soon warms up a bit!

No comments:

Post a Comment