V3 90 deg 'Jota' Engine big bore

[Roger B]

'Valve cages can give sealing problems, especially with different thermal expansion. unless you are looking at serious use seats directly in the head will work.'

If the, probably aluminium, cylinder head expands more than the bronze or cast iron cages you will get leakage problems. Unless you are intending to use this engine for power production or racing valve seats cut directly in the aluminium head with separate bronze or cast iron valve guides will work well. If you make the cylinder head section from cast iron it may weigh more but you can have the seats and valve guides cut directly in it which may allow you to reduce the dimensions and the weight.

Every engine design is a set of compromises     

[AlexS]

ah yes the heads would be out of aluminium. mmm okay seperate valve seat/guides.

Lets try a calculator. delta 300 deg C

Material: Aluminum 20.000mm
Change in Length (ΔL): 0.1332mm
Final Length (L + ΔL): 20.1332mm

Material: Bronze Round 20.000 mm
Change in Length (ΔL): 0.108
Final Length (L + ΔL): 20.108

Material: Bronze 20.050 s6 tolerance
Change in Length (ΔL): 0.10827
Final Length (L + ΔL): 20.15827


Agree there should be a leak path of when there is not enough  press fit tolerance.

Every engine design is a set of compromises     

Agree! And that is the fun and tough bit of designing. Several ways of doing stuff.
Like the idea to use cast iron heads, only not sure how to turn seat valve in my mill

[Roger B]

I made a simple cutter for the valve seats. As they are somewhat recessed in this design turning or milling was difficult.