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An engine overhaul - much remains invisible at first

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Created on February 19, 2026

Text:

Martin Sigrist

Photos:

Martin Sigrist

37

Martin Sigrist

37

Franz Durrer at his Prince Engineers Ltd crankshaft grinding machine

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Graham-Paige 619 (1929) - stood in a shed from 1955 to 2006

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Graham-Paige 619 (1929) - The car from first Swiss ownership has 95 percent of its original substance preserved

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The cast bearings of the old connecting rods show chipping in the material

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The corpus delicti - breakouts in the cast connecting rod bearings

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The engine remained untouched during the overhaul - picture from the photo box

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Parts are machined here, not simply replaced

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A small part of the machinery at Franz Durrers Motoren Mechanik AG in Neuheim

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The starting point in spring 2025, the dismantled Graham engine

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The engine disassembled into its individual parts

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No extensive damage

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The bearing surfaces of the mighty Graham-Paige crankshaft are ground over

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The crankshaft is placed on the supports before being clamped in the chuck, the left-hand shaft journal is fitted with a clamped driver so that the shaft rotates during machining

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The driver on the crankpin allows the grinding wheel to swivel when the crankshaft rotates

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How is the crankpin ground?

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Normal wear on the bearing surfaces

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The grinding wheel swivels to grind the crank pins, the driver is visible directly above it

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Franz Durrer is well supplied with work

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During machining, the shaft always rotates around the longitudinal axis of the main bearings, even for the crank pins

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Durrer's pride and joy is the Prince Engineers Ldt grinding machine

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Sliding bearing blocks prevent the shaft from bending minimally when the grinding wheel exerts pressure on the shaft

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Freshly made connecting rods, pistons from Cadillac, Mercedes bearing shells, new valves, NOS timing chain in original box and planned cylinder cover

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New parts or New-Old-Stock NOS - the best starting point for a rebuild

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New main bearing shell specially manufactured by Durrer in the dismantled bearing pedestal

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New connecting rods milled in-house from solid material with matching off-the-shelf bearing shells

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Bearing shells for the newly manufactured connecting rods from the Mercedes parts range

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The finished engine block awaits the crankshaft drive including pistons, camshaft and valves

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The engine block is upside down on the cleaning table, the main bearings have been provisionally fitted

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The valve guides were left as they were, the engine has four (?) intake and six exhaust ports, hence only ten holes

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Meticulously cleaned engine block of the Graham-Paige engine once designed by Continental

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Enjoy the sight of a perfectly intact engine block with new bearings

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In 1929, seven crankshaft main bearings in a six-cylinder engine were a challenge to the precision of the engine builders

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Two Mathis engines, Neuhheim has experience with pre-war side-valve engines

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Individual cylinder heads from Zuffenhausen

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Twin-disc clutch and bell housing, intake manifold and timing cover during disassembly

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The aim would be for the Graham-Paige to be back on the road in the summer

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Summary

Overhauling a pre-war engine requires a great deal of specialist knowledge and experience. Numerous peculiarities have to be taken into account, but the quality of the work usually only becomes clear over a longer period of time. One expert address is the workshop of Franz Durrer Motoren Mechanik AG in Neuheim in the Swiss canton of Zug, where the master mechanic let us look over his shoulder.

This article contains the following chapters

Do just one thing - but do it thoroughly!
Bearings and connecting rods manufactured in-house
Respect for old communities
No shine for shiny work

Estimated reading time: 9min

Preview (beginning of the article)

An engine overhaul is a matter of trust. After all, much of the work that is carried out is no longer visible, let alone inspectable. Freshly painted and with adhesive tape on the intake and exhaust side, the fuselage engine will eventually be back in place, waiting to be installed and fitted with its auxiliary units (or vice versa, depending on the space available). Whether it will then last will only become apparent when it is needed and required - and for how long is a completely different question.But what comes to light when you delve a little deeper into the subject matter in the middle of the revision and are able to extract some information from the professional about his wisdom and tricks? All kinds of new insights!

Welcome to Zwischengas!

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