Engine head progress

This weekend I have made some progress with the engine head. The inlet and exhaust ports have been polished and valve seals have been pressed in. It all went quite nice together. I used some Dremel tools and polishing compound to polish the ports in the inside, with extreme care to not damage the mating surfaces for the inlet and exhaust and valve seats. On the pictures you can see the dedicated fixtures to press the valve seats and guides into the head.

The upper assembly with the camshaft carriers and little brackets has also been put together. As the top of the engine will be open, it will be possible to see any leaks or other issues inside the head. The brackets are only for the test engine as the V8 holds the cam shafts with the head covers. 

The valves were almost finished, I just had to grind the top and bottom surfaces to final dimension. So they are ready to install. The material for valves is SS AISI 316.

During the week I expect to finish the bores for the cam shafts, including the bronze split bearings installation. Also the countersunk on the valve seats.

Lower engine assembly

I have virtually completed the lower assembly of the engine. The crankshaft is finished and finally assembled with con rod inside the crankcase. 

You can see that the crankshaft has 6 holes on the counterweight area. These will be filled with tungsten bars. This is to adjust the amount of weight on the counterweight as well as keeping the inertia low. On the V8 one I might not do it as it is a lot of hassle as the tungsten is really hard to work with. I have to use a right angle grinder and because the pieces are so tiny it is quite a dangerous job.

The bolts to on the con rod are M2. I will replace the current stainless steel by 12.9 steel ones.

The cylinder liner is from a Lapped internal H7 steel off the self tube, that I turned to fit the aluminium engine block. It is not hardened but I hope it will be just fine for this test engine.

I am going to use gasket sealant, like Loctite 5800 as I do not plan to use any joints on between the crankcase and engine block.

Piston machining and con rod assy

Today I have finished machining the piston. It has been a long process which started on the lathe and has finished on the milling machine.The difficulty of manufacturing this component lies on the amount of features and accuracy required.

In terms of design it is a complex exercise, especially as boundary conditions are unknown at this stage. I have based the loads for a max. of 14000 RPM for inertial loads, pressure cycle is based on a conventional 4 ST IC engine, but adjusted to the IT3 engine. The piston is subject to 3000 g at 14000 rpm

All in all, the loads the piston see are 820N in compression and 391N in tension (that is 83,6 Kg, 39,9 Kg). This is quite extreme and is mainly due to inertial loads and pressure gradients from the combustion cycle. Temperature wise I have estimated 250C, which reduces the material strength. The diameter has been reduced to account for expansion of the piston with temperature.

The piston pin has a slight tight fit on the piston and H6 on con rod. The piston pin is secured by two elastic clips that sit on a groove. The groove is machined with a custom made tool, as shown in the next pictures. The initial development of the piston will focus understanding better the boundary conditions (RPM, temperature, etc) and how the piston performance is affected (wear on friction surfaces, distortion, etc)

Above is the piston blank after turning operations (right) and milling fixture in PA (left)

This is the piston during machining on the 3 jaw chuck used to fix it.

Above is the custom made cutter to machine the piston pin clip groves.

Piston and con rod assembled. As you can see there are neither piston rings nor piston pin clips. The con rod bolts are not final ones either. Piston rings are off the shelf from Honda. there will only be 2 compression rings, and no lubrication ring.

Next is the final stages of crankshaft machining and assembly of it with cylinder and con rod / piston assembly. With that I should be able to start feeling the compression of the piston moving up and down the cylinder.