Technical engine information

Hi all,

I rarely post here but have always found this site and the cars interesting, I have a technical automotive background so I am looking for some details that are not often discussed. I am from the Porsche world and they have or had official technical booklets for the older models that came out in the 80s and 90s. It gave details like camshaft specifications, somewhat limited but it would give duration and lift, I would also detail items conrod length, wrist pin diameter, valve diameters, bearing diameters etc. I haven’t found anything like this on the 456 or later related series? Have I missed some low hanging fruit? Or aren’t these details commonly available?

I have always loved the 456 GT and might be getting close to buying one, I only like the early cars and I like in regards to older cars I love applying modern technology to them. I am currently rebuilding and modifying a Porsche 928 engine and have removed around 8 kilos or rotating and reciprocating weight by using essentially NASCAR parts. I am also building a full inconel exhaust.

I have always wondered if the bore can be increased in the 456? Standard it’s 88 mm why not like the 812 Superfast? Which is 94mm. The 928 started out at 95 mm and a friend in the US has one that was taken out to 109 mm, with the stroke improvement, he has 7.0 litres but 7.5 litres is possible baring in mind the engine started out at 4.5 litres in 1978. That is a fair amount of increase. For the record the amount of stroke chosen can depend on the amount of revs desired at the top end.

Just from what I could glean from photos the 456 engine seems to be designed to somewhat restrict ultimate power and allow future development. Any further information would be appreciated.

Cheers GG.