Alex170984 wrote:I need to weigh up if the smaller rods, smaller crank and 18mm pin pistons are a better alternative to spending money on bigger 20mm pin pistons and using the 42mm crank. I can get stock 42mm rods easily for £50 from a reliable source so that's not an issue.
Is there anyway I could have the 18mm pin pistons bored out to suit the bigger rods and have a floating pin installed? Or has that already been suggested? I'm a bit lost now lol
remember... in the end this is YOUR project... we can only offer you advice.
It is kind of funny that you begin with, "I need to weigh...." because that is the advantage to the 40/18 crank/rod/piston combination... a mass savings of well over 2 kilos!
You can have the 40/18 rods opened up to accept a 20mm wrist pin, but opening it larger to accept a bushing, that will likely mean the small end is too thin. Again, a fixed wrist pin worked, and although not as good as a full floating pin, there are many 4AGE engines making good power on fixed pins.