[knighty]

Hi bob, interesting discussion this one………correct, they reduced the stroke in order to reduce the piston side loadings as per my notes above, therefore reduced friction = more power.........they cant get too clever with the standard block, as they MUST use a factory cylinder block, as per the ACO rules.......hmmmm, dont mention the C5R specially cast blocks!!!!

ref the liners, they fully machined out the iron liners, and nicasil coated to the parent cast ali of the cylinder block

sorry again, Katech and GM DID design for low revs and low friction, this is principally achieved by the big capacity and the long stroke……….Roger Allen did a 12 page technical summary in the may 2007 issue of race tech magazine stating exactly that, low revs = low friction.

believe me, the 7 litre LS7R and Elan GT1 7 litre race engines are very long stroke for their capacity, going by most US tuning standards, particularly Nascars…….heres the proof, lets compare the bore to stroke ratios

Corvette LS7R: 4.185" bore / 3.875 stroke = 1.08

Elan/Saleen GT1 4.125 / 4 = 1.03

5.8 NASCAR: 4.125 / 3.250 = 1.28

Both the Corvette and Elan 7 litre motors produce 640lb/fs (860Nm) of torque……..thats a ferocious amount of torque for a gasoline engine

Yes I'm comparing 5.8 litres to 7 litres, but it’s the bore to stroke ratio trend that drastically changes for a heavily restricted GT1 / LMP1 engine……..the nascar motor has a much bigger bore, for the stroke, as they are chasing power and revs, they don’t necessarily need the torque as they spend nearly all their life at max power on ovals……..acelleration out of a tight corner for a nascar engine is not really a consideration, otherwise it would compromise the top end power.

The reason the Corvette regularly dusted the Aston martins, was because the astons just couldn’t compete with corvette on terms of torque, hence the restrictor rows, but thet still didn’t fix things, as at the end of the day, the aston was 5 litres, and therefore 2 litres smaller!……..to compare the Corvette to the Audis is like an apples to banannas comparsion……..Aston have the wrong engine and they know it……..I'm hearing they want to take the 5 Litre V12 LMP1 racing……..I hope they remember the lessons learned against Corvette and go the biggest capacity possible (6 litres) and go long stroke, as it wil rev lower.

all the best :-)