Last week's posting, Engine Part I, was about the general features of the Alfatross' 1975 cc four cylinder Super Sprint engine and the differences between it and the more pedestrian engines installed in other 1900 Alfas. This post is going to delve into the inner workings of the engine and how we're going about making sure that beneath the Alfatross' beautiful skin its beating heart runs strong and true.
The Approach
The Alfatross was built to race, and we want it to be race-worthy when the restoration is complete. It follows that functionality will be emphasized. Some authorities would say that maintaining originality trumps other considerations, but the 1900 engine has known internal design defects that can be corrected during the rebuild. My view is that we would be doing a disservice to The Alfatross not to correct these internal problems while we have the opportunity. There are other departures from originality that will improve performance and longevity such as the application of special coatings that reduce friction and even chemical and physical treatments that allow the re-use of original parts which might otherwise have to be replaced. This is where I am relying on the expertise of DeWayne Samuels, who is directing the engine work in Phoenix. The following is a distillation of his various progress reports, broken down by component groups.
Engine Block
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| After cleaning the main bores and mating surfaces of the block the main bearing bore diameters were measured and checked for core shift and alignment. These dimensions tell us how true the crankshaft will run in relation to the cylinders, and also will indicate if there has been any core shifting or problems with the main web or main cap. |
The initial measurements indicated that new main studs and fasteners need to be installed first to obtain proper loading during measuring and correction procedures. So the main studs were extracted, measured, profiled, and sent out to a vendor to fabricate new custom-made stud and fastener assemblies. The threaded female stud bores in the block were also analyzed and repaired where needed.
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| The cylinder walls and deck surface were subjected to sonic testing to determine thickness and integrity. This test tells us the amount of material available for overbore with relation to wall thickness, concerns for cylinder deformation, and cooling/heat transfer. The results show that the cylinder block assembly has plenty of life left. |
Cylinder Head, Valves, and Cams
The combustion chamber volumes were measured and recorded as were the volumes of the piston domes and valve reliefs. The valve spring retainer/adjusters could not be assembled without first fabricating a tool. The cam bearing journals were prepped and measured to determine clearances. When the camshafts themselves were cleaned and inspected it was apparent that one lobe was badly worn and will have to be repaired. Additionally, all the bearing journals were pitted.
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| The cylinder head was disassembled, cleaned and glass bead blasted. It was apparent that cylinder No. 3 had sustained damage. Valve seat wear was assessed for all cylinders. A special tool had to be fabricated to measure spring heights and seat location in the head. |
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| Measuring the piston dome and valve relief volumes. |
Pistons and Crankshaft
The piston domes, wrist pin locations and offset, deck heights and pin heights were measured along with combustion chamber molds and volumes. When the pistons and cylinders were checked for wear, piston no. 3 was found to have irreparable damage. So the Alfatross is going to get a new set of pistons. The crankshaft's main bearings had damage attributable to poor lubrication (one of the known design deficiencies of the 1900 engine) in addition to a potential crack. It may be necessary to send the crank out for nitriding to treat the bearing surfaces.
By the Numbers
The Alfatross' heart is not exotic or complicated, but even a simple engine takes a lot of time to break down into its component parts, and clean, measure, and compare them with the original specifications. So now we have a lot of "baseline" numbers and dimensions for the main components of the engine, and it is clear we have a lot of work to do. Although I have not yet discovered incontrovertible evidence that The Alfatross was raced competitively, at least some of its previous six owners must have driven it pretty hard, given the evidence of use and minor rebuilding in the past that we have discovered. The good news is that it looks like the pistons are the only parts that need replacement--so far!
