Sonett community forum

upgrading intake/exhaust valves


Hi folks,

I have been working with a friend in the past few months to improve the current status of my 73 sonett III's engine (1.7L).

Besides replacing all the gaskets, seals, wires, water pump, fuel pump, and other peripherals on the engine, we are now contemplating getting bigger valve size than the stock ones. I have a machine shop lined up who is familiar with this engine type as it was used on forklift as well.

I have been searching the web for clear information about what size to use, where to source them (p/n, brand...), hardened seats,  what springs to upgrade the heads with, do the pushrod need to be changed (based on valve length, if yes, what p/n to use), etc.. and if there is a better camshaft to use for increased duration/power  (if yes, where to source, p/n, etc...).

For now, I saw a few posts of people having done these changes, but sadly no real information about the parts themselves so that another person could do the same mods.

I've found that there's a booklet by Jack Ashcraft titled "Total performance V4" but didn't see any extract of it  online about what it really contains. Is it specific enough that you get part numbers for you to order your own parts? Does any of you have this booklet, maybe as a pdf? I tried to reach out but received not reply concerning the content itself. Is it worth acquiring?

I've searched this forum and also looked at the "sonett mods" section but didn't find these type of information.

So I thought I would start a new thread in hope that I could get some help with this.

Thank you



You could call Mark Ashcraft (just google him) and get all the info you need.