72 cc V8 project

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Jun 6, 2022
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Project of a mini V8 block that could be used as a base for an RC dragster if everything goes well: Displacement 72cc, 200mm long, flatplane type, 24 bore and 20 stroke. It is planned to have a distribution by 4 OHC, liquid cooling, carburetor or injection and electronic ignition. As I don't know anything about foundry, everything is cut in the mass with traditional machining (basic lathe and milling machine with DRO).

The design is simplified and the number of parts is reduced to the strict minimum (for a V8!!!): one-piece crankshaft directly turning on the crankcase, connecting rods with a cap without bearings or rings, single-ring piston, OHC driven by toothed belts, valves and tappets co-axial under the camshaft, valve seats machined directly in the cylinder head and no guides attached. Some pictures of the beginning:

The engine crankcase cut in a 80X80 block, for the finishing, light sandblasting or polishing we'll see later...

The 2 cylinder blocks with water passages and inserted sleeves. These are made of 25CD4S tube, the original surface condition is good and the dimension regularity is in the 1/100, I won't do better, so used as is, it's time saved...

The one-piece crankshaft with its lubrication channels, the connecting rods with lightened caps and pistons.


Prototype of titanium valve

Next work : machining of the 2 cylinder heads with 16 valves to adjust, camshafts, oil pump....still more than 2 years of work before first starting, I think. !!!!
Amazing work ! What did you do before you retired ?
Thanks for your interest,
@ PeterDRG: my previous job, health facility manager...... nothing to do with machining;)
Why titanium for the valves?
I get that there is a satisfaction in making them from a difficult material, but when you're running in aluminium seats and guides, there can be no need for ti valves, is there?
hi Peter,

Yes, the test of titanium for valves is based on non-rational arguments like working a metal that has the reputation of being complicated to machine and making a "factory competition" engine like .....
The properties of titanium seem to be well adapted to this use, although I haven't tested the interaction between aluminum and titanium yet...
The good surprise is that turning is not as difficult as expected, just time consuming, with the parameters: well sharpened HSS tools + low cutting speed max 5m/s + oil lubrication. Not more difficult than stainless steel, anyway.