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I’ve got my hand on a spare 205 XS cylinder head and I’m looking at modifying for my 205. The two roads I am looking to go down are eather 1. Keep it fairly standard but get it gas flowed, inlet matched and just generally refurb it maybe also get some sinus valves for it or skinny down the ones I have. 2. Same as above but... Go all out and as a bit of a project over the winter fit the valves out of a TU5. Now i I was wondering if anyone has tried this? Or if it’s a stupid idea, waste of time, not possible etc.... Ive mocked up what the bigger valves look like in the picture below. My concerns are valve to cylinder bore clearance and “shrouding” around the inlet. what do you guys think? Cheers

A little bored given the crappy weather, and mindful of the mileage my 205's original engine is racking up, I was thinking of building up a higher compression 8 valve lump for my 205, 1.9 with 1.6 pistons, and am wondering what the limitations of the standard top end is, and would standard bottom end parts work as a budget build without grenading given the 8 valve tends to produce its power at lower rpm? the questions I have are as follows: at what point does the head need work, would I benefit significantly from doing so at a fairly low level of tune? IIRC I do have a lightly tickled 8 valve head in the shed already, the exhaust ports have been smoothed up a bit I am thinking as with most pug engines and going from what I have seen of Sandy's engine builds is that the valves are plenty big enough (though I'm off to read this topic again shortly... http://forum.205gtidrivers.com/index.php?showtopic=31290&st=0 ) a quick working from memory of dish and chamber volumes indicate that I'll be around 10.8-1 with an unskimmed head, no doubt the head I have has been skimmed in the past. what is the max lift for std valve gear? I take it that RPM is more a bottom end concern given the tappets are solid as standard. for the bottom end, I am thinking as mentioned of some XU5JA pistons as they have a smaller dish and bump the compression, some standard 1.9 rods checked for weight discrepancies. I do have an XUD9TE crank to hand which is reputed to be forged steel. I have an XU7 block to hand, and an XU7 oil pump, as well as XU9j4 10J4RS and XU10J4 oil pumps. Camshafts, not sure what I could use, may depend on limitations of standard valve train, IIRC I do still have a PTS max Torque cam if it has not rusted away in the garage

I posted this in the other video's thread but think it's worth it's own topic, purely because the amount of ground it covers. Some of you may have read vizards book, whilst this concerns the A series engine, it references topics we regularly discuss in the modified engine section up to and including. He generally explains things pretty simply, and if you want to understand a bit more about a number of topics including those below, watch it. Filtration Fuel atomisation Compression ratios Dynamic compression ratios Brake Specific fuel consumption Porting Valve design Valve seat design including 3 angle valve modification Lifter / bucket diameter Roller rocker design and limitations Ramp angles on camshafts Cam shaft timing Carbs vs injection (lucas mechanical) Valve shrouding Bigger vs more valves Decking blocks Squish height Burn time Rod lengh / ratio Octane ratings Water injection and some more that i can't remember Cheers J