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Inspection of the Engine Bottom End - 2013

The origins of the my Aprilia's engine has been a bit of a mystery. According to the invoices from the UK restoration during 1990 - 1993 in November 1990 there was a "new " block sourced from somewhere. Then in January 1991 another block was set up and tested as the other was damaged! In February the block was sent away to be line bored and honed before the engine was assembled with new pistons (p/no. 2047/VI 0.75) a number I haven't been able to track down, along with new valves, cotters, head gasket, small end bushes & re-metalled big ends. When it was assembled they ran it on a dyno, unfortunately I don't have the results of that test.

At a later date the head had hardened valve seats inserts to enable it to run on unleaded fuel. Since I've had the car the engine hasn't been touched, well I did take the rocker cover off to admire the wonderful overhead cam & valve setup, painted it the correct black and made some original looking bolts!

In August 2013 in the UK Stuart Tallack's Aprilia broke a con rod that smashed through and destroyed the block. Since then the LMC forum has had some interesting discussion on the reliability of the original alloy rods verses new steel rods which has given me a few sleepless nights as I have no idea what my engine had. So it was time to take the sump off and have a look!!


Removing the beautiful cast alloy sump was fairly easy, drain the oil, undo the 12 bolts to the engine block, the two bolts that fix on to the gearbox and carefully lower it. First thing noted is the con rods are the original alloy type, they look alright but without getting them crack tested how can one tell? A careful inspection revealed whoever put the engine together certainly knew what they were doing. Properly fitted split pins and wire wrapped bolts show a lot of care was taken, so my confidence has risen. The camshaft chain is the later 2nd series roller type and modern oil seals have been fitted. The flywheel has some teeth wear. There was just a small amount of oil sludge in the bottom of the sump, no nasty bits of metal, even better. With that I decided to go no further and left everything in place, if it ain’t broke etc...

Curious collection of Numbers

The original engine number was 1507. I knew the block was from 1938, it has the little Lancia 1938 stamp on the outside. The engine number stamped on the normal position is 3414, without the the 97 prefix! With the sump off this number was found 6998, curious? The main bearings caps are stamped 2305 and 1646.  Most other parts have the oval 1937 Lancia stamp. The crankshaft has the normal ‘Equilibrat’ balanced stamp but has a date stamp from 1951, shows that Lancia continued to make some new 1st series spares into the 1950s. My guess is the engine has been rebuilt on more than one occasion and is now a mixture of parts from at least 3 engines that, so far, all work very well together.


There is evidence of a number of repairs to the block. You can just see some alloy welds up near the top and a large chunk has been welded back in on the bottom side. I found a small crack in the sump, when the clutch seized and a spring broke it appears to have dug in there and caused the damage. As it’s in a non structural spot I drilled the end of the crack to stop it traveling further and used some J.B. Weld for a repair. The sump had been bolted directly into the block so I made some new studs and nuts. On re-assembly I sealed the joint with Loctite 596. A quick run to check that the oil pressure was still there and a longer test run to test for leaks, which there weren’t.


December 2013