Pecos Pete
08-17-2006, 05:39 PM
Anyone done this before?
4.8L crank stroke (3.268")
4.8L rod length (6.275")
6.0L block bore (4.000")
Yields approximately 327 cid with a HUGE rod/stroke ration of 6.275/3.267 = 1.92:1
http://ourworld.cs.com/jrp98ls1/LS1_bore_stroke.jpg
If I use 6.0L pistons made for the stock 6.098" rod length and 3.622" crank stroke, but instead use the 4.8L rod length of 6.275" and 3.268" crank stroke, I believe the piston will end up at the same compression height at top dead center.
If I use 61cc chamber (5.3L) heads, and flat top pistons, I calculate I will end up with a compression ratio of about 12.2:1.
If instead of flat top pistons, I use something like Diamond Racing's domed 6.0L pistons with a 10cc dome, I believe the 61cc chamber heads effectively become 51cc heads, and I calculate I will end up with a compression ratio increases to about 14.5:1.
Would this be a good purpose built LS1, LSx, GEN III E85 motor? E85 is 105 octane alcohol. I believe alcohol likes a high compression ratio and a high rod/stroke ratio. This combination of parts looks to be able to produce both.
If I use stock GM rods and impose a piston speed limit of 3500 feet/minute like typical GM cast connecting rods, this becomes approximately a 6500 rpm red line motor.
If I locate some stronger after market rods and impose a piston speed limit of 4000 feet/minute like typical GM forged connecting rods, this becomes approximately a 7500 rpm red line motor.
Anyone know of a source for forged 4.8L (6.275") connecting rods?
Can anyone find any flaws in my thinking here?
4.8L crank stroke (3.268")
4.8L rod length (6.275")
6.0L block bore (4.000")
Yields approximately 327 cid with a HUGE rod/stroke ration of 6.275/3.267 = 1.92:1
http://ourworld.cs.com/jrp98ls1/LS1_bore_stroke.jpg
If I use 6.0L pistons made for the stock 6.098" rod length and 3.622" crank stroke, but instead use the 4.8L rod length of 6.275" and 3.268" crank stroke, I believe the piston will end up at the same compression height at top dead center.
If I use 61cc chamber (5.3L) heads, and flat top pistons, I calculate I will end up with a compression ratio of about 12.2:1.
If instead of flat top pistons, I use something like Diamond Racing's domed 6.0L pistons with a 10cc dome, I believe the 61cc chamber heads effectively become 51cc heads, and I calculate I will end up with a compression ratio increases to about 14.5:1.
Would this be a good purpose built LS1, LSx, GEN III E85 motor? E85 is 105 octane alcohol. I believe alcohol likes a high compression ratio and a high rod/stroke ratio. This combination of parts looks to be able to produce both.
If I use stock GM rods and impose a piston speed limit of 3500 feet/minute like typical GM cast connecting rods, this becomes approximately a 6500 rpm red line motor.
If I locate some stronger after market rods and impose a piston speed limit of 4000 feet/minute like typical GM forged connecting rods, this becomes approximately a 7500 rpm red line motor.
Anyone know of a source for forged 4.8L (6.275") connecting rods?
Can anyone find any flaws in my thinking here?