...this reads to be a test of a number of possible workrounds that REME in Normandy came up with to deal with the valve/top end aspects of the issue.This vehicle had been fitted with new standard pistons and rings. It was also fitted with two re-built exhaust valves, one modified Bedford exhaust valve and three re-faced standard Austin exhaust valves.
The vehicle was driven over normal roads, including two fairly steep gradients. For the first 300 miles the performance was good. The first sign of roughness occurred at 350 miles and this grew steadily worse until, at 480 miles, two cylinders began to miss badly. At the conclusion of the run, reasonable compression could be felt on all six cylinders.
Engine oil pressure was 48 lbs per sq. in. at 30 m.p.h. with an engine temperature of 160° F at the commencement of the test. This dropped to 40 lbs per sq. in. at the same temperature and speed after 150 miles and then remained consistently at this figure throughout the remainder of the test.
On completion of the test the cylinder head was removed for examination. It was at once apparent that heavy oil burning had been taking place. The combustion chambers of Nos 3 and 4 cylinders had a heavy deposit of carbonised oil and the sparking plugs were heavily oiled. There was an appreciable hard carbon deposit on all other cylinders.
All inlet valves were in good condition but the exhaust valve heads were distorted in all cases, and there were signs of pitting. One of the built-up valves was showing definite signs of leakage. There was excessive oil present on the guides of Nos. 3 and 4 valves.
But it was a failure It looks as if none of the kludges held up to the rigours of the test...and they had tested them in the face of the worst deeds of the culprit -"this vehicle had been fitted with new standard pistons and rings". And the piston/ring problem beat the best efforts of REME with what they had at their disposal in France
So...the affected vehicles REMAINED "at present frozen in V.R.Ds" until the end of the testing period on "..3.12.44..." - when "new and interchangeable piston rings of improved material and design should be incorporated into production now, and fitted to the 3,000 vehicles at present frozen in V.R.Ds".
The "test period" itself had lasted from some time before the 8th of November 1944...
A representative of D.M.E. attended a meeting between T.T.2, C.I.E.M.E. and the Manufacturers on 8.11.44. The manufacturers offered new and completely intercahngeable piston rings, both for new production and re-working of "frozen" stocks of new vehicles. Tapered Compression rings (2 off) in D.T.D. 485. Scraper rings (1 off) in D.T.D.233. Tests on three vehicles fitted with these rings show satisfactory oil consumption and a steadily rising m.p.g. at 2,500 miles. It was agreed that in view of the satisfactory preliminary results and complete interchangability of rings, the new rings could be introduced into production as soon as supplies are available. It was also agreed that if the test results continued to be satisfactory after 5,000 miles re-working of the "frozen" bank of vehicles with the new rings might commence.
....to the 3rd of December 1944.
And THAT was the official end of the Austin K5 problem in Normandy, as far as the Director of Mechanical Engineering at the War Office was concerned...having found a cure that involved "new and interchangeable piston rings of improved material and design".
Less blowby to contaminate the HD30 oil...which could therefore carry on being used; as could the "standard" (standard that is for the "assault" K5s) increased-clearance "wading" pistons. No contaminated, heavily-graphited "dirty" oil circulating around the engine creating high wear rates in the top end. No coking up of the valves or the combustion chamber, no oiled-up plugs.
And just to square the circle on the above - I doubt there is much coincidence to the fact that there were 1,400 Austin K5s in "wading" kit provided for issue before the start of June '44 to assault GT companies for D-Day according to other details that Tom found....and 1,400 Austin K5s in Normandy affected by problems of faulty parts and accelerated wear three months later; some with as little as 2,000 miles on "new" engines.
It's also worth noting that Tom had also discovered and recorded on the lorry thread on ww2talk that 1,400 K5s were pulled and prepared for issue to the assault companies in May '44...by Austins themselves...I wonder if THIS was when the increased-clearance "wading" pistons were fitted???
Finally - the issue of the change to MT 80. We know from various locations and histories that this change on the eve of OVERLORD did cause problems...and that litany of valve problems on the REME "test" K5 does mention two symptoms of overheating/poor cooling of the valves - the pitting of the valve faces and the "definite signs of leakage" I.E. the valves not dsealing on their seats. It's a bit "chicken and egg" whether the SECOND of these would be down to the valves burning OR the valves rocking around due to the guide wear ....but pitting on the valve faces would be a sign of overheating/poor cooling all right...
One of the British Army veterans on ww2talk confirmed that the Austin manual for these engines (in 1946 at least!) DID contain instructions for advancing for retarding the ignition timing to match the fuel used...so as a problem this one was easily dealt with. But it IS interesting that Austins (and I presume the War Office!) thought it essential to fit "wading" pistons with increased piston skirt clearance to deal with extra thermal expansion A MONTH before D-Day! THAT is definitely "last minute" stuff!!!
So - one set of problems brought on/complemented the other??? Need for increased piston skirt clearance due to overheating in waterproofed engines -> fast bore/ring wear 'cos the new pistons used the old design/grade of rings -> high oil consumption AND carbon blowback contaminating engine oil -> worn valve guides...which are ALSO going to be hit by overheating issues anyway because of the MT 80...
It's worth noting that from everything I've read, and comments from several members on ww2talk - that while altering the timing on internal combustion engines to prevent pre-detonation etc. with higher-octane fuels is one action that's necessary...it doesn't ACTUALLY make the engine run any cooler! THAT is a problem that an engine still has to cope with....or in the case of the K5, exhibit overheating valve issues as well as worn valve guide issues.
However, looking at that final closure of the book on the K5 problem as of 3/12/44 by the War Office - I think we have to assume that the overheating issues brought on by MT80 were "officially" thought to be by far the lesser issue involved compared to the damage done by the fast-wearing piston/rings issue. Once THAT was addressed, the K5s could handle a little overheating...???
(I put that last caveat in there, because the K5 doesn't seem to have had that long a career in the British Army after the war, it seems to have vanished out of khaki toot sweet! The K6, with the same engine but lower compression and lower power output had a MUCH longer Cold War career in many and various uses and is still favoured by restorers today...maybe it ran cooler? )