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Originally Posted by 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
all the best :-)
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I do not disagree with the long stroke/low friction as it is the only method they can use to gain an advantage with the crippling effect the restrictors have on standard hot rodding techniques.
I would say on four forty bore centers, without iron liners, Chevy and Katech "tuned" not designed for the bore stroke ratio they are pretty much confined to, as on four forty bore centers, minus iron liners, which are stronger than aluminum walls they cannot go much thinner and have practical safety margin in an engine designed to last a twenty four hour race
(I am well aware that some engine builders, depending on application, are taking cylinder walls a good deal less than twohundred thousandths, depending on make of engine and rod length.)
Remember Dodge was forced to quit using the true stock based engine block in NASCAR as its thicker cyl. walls gave it what NASCAR considered an unfair advantage.
Instead they were forced to switch to the block created originally for sprint car racing.
The crippling restraints of the small bore centers is one of the reasons Ford is bringing out the Hurricane engine, with bore centers rumored to be at least four fifty and possibly four fiftyfive.
What compression ratio are they running on the bunny pee gasoline?
Bob