Author Topic: increasing the displacement (Read 2252 times)

Maddog · « **on:** November 21, 2007, 07:07:56 PM »

I know there are a couple of kits out there to increase the displacement but they seemed very expensive. I was wondering just what was available, how big can you go, I basically want to know all tthe options available before buying owt.

please be as helpful as possible with links, technical details, links to abarth specs and any other options, ie suitable bike pistons/rods and rebore

all help will be much appreciated, Richie

bis13 · « **Reply #1 on:** November 22, 2007, 09:23:08 AM »

have a look on the 500 mania site in links

MaLi · « **Reply #2 on:** November 23, 2007, 02:57:47 PM »

On standard 650 cylinders you can go up to 79.0mm bore without worrying about thickness of the cylinder wall. There are people in Poland who put 80.0mm pistons but then sometimes cylinder wall crackes causing damage.

I had 80mm Bis pistons in the cylinders which were bored and new liner (I think that's the right word) was inserted. Engine block had to modified too. BIS psitons are 6mm lower - from pin axis to the top of the piston. This means you have to modify push rods and tubes they are in - 2h job - as well as few other things depending on how much you skimmed your head. Good thing is that BIS pistons are lighter than standard ones by around 10-15g each - as far as I remember.
Problem I had on a setup like that was that it was overheating alot so you will definately need an oil cooler.

You can also go for VW cylinders with 85.5mm (or more) pistons. But I never tired it myself so all my knowledge is purely internet based.

Hope that this is usefull.

Regards,

Mali

ps. what sort of power you want to get?

Maddog · « **Reply #3 on:** November 23, 2007, 05:33:17 PM »

Hi Mali, thats the sort of info I'm after, the only stuff I've been able to find is stupidly expensive like gersts 6K euro for an 833 stroker kit, I could get a complete rebuild of the GTO motor with forged internals for less than that, its just stupid money. I'm not reallu after any specific power figure, just more displacement and more torque without building a 8000rpm screamer.

I've the possibility of getting a small supercharger cheaply with a carb set up so would like to build a suitable bottom end

Frothy · « **Reply #4 on:** November 23, 2007, 08:09:13 PM »

Wow MaLi you've got some very technical info there.

Frothy