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Okay, I'm thinking about that 402 from SLP. With a decent cam (230/236 .575 114LSA) and good heads (warmed up 6.0 ones) I figure it should make an honest 425-450rwhp and some absurd rwtq around 550 or so.
With a normal weight of around 5300lbs (appx) my truck should run 13.25@102 MPH. OR around 8.6 in the 1/8th mile around 85mph.
Anyway, I did some math with the gearing of the 4L60E and shit as well as with what gears I'm looking at either the 4.10:1 or 4.56:1. Well with a 4.56:1 I'd be into 3rd gear in the 1/8th already and cross the traps around 4000rpm in the 1/8th. If I still went on to run a 1/4 I'd cross around 4900rpm...If I ran a 4.10:1 I'd be around 5800rpm in the 1/8th which is better than 4000rpm. I don't want to rev to 6600rpm in a truck even if I have the cam to support it...I have a 402, it's got TQ out the ass I don't need topend HP.
From my memory you want to be at the top of the powerband when going through the traps and a 4.10:1 would be about 600rpm less in the 1/4 vs a 4.56:1 but I could honestly give a shit about running to 110mph in a big truck.
So it looks like a set of 4.10:1 gears would be better for the drags AND economy...
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I'm new to this site and far from an expert on racing these trucks, but have been around drag racing a while so here is my :twocents:
Yes, you want to be at the top of the powerband when going through the traps. But, sometimes the gearing to do this can hurt you off the line. Too much torque multiplication from a low 1st tranny gear and low rear end gear combined with a high TQ motor, could mean trouble getting traction.
Lots of 1/8 mile drag cars switch to 2 speed powerglides and run faster than they did with 3 speeds because of this. They just blow the tires off in 1st gear and immediatly shift into 2nd with the 3 speeds.
I would stick with the 4.10's unless you need the extra gearing to get off the line. But with the low 1st of 4L60's and 550 rwtq I don't think it will be a problem.
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If it makes a difference I am running 33" tires and will be launching in 4wd Hi. :hshake:
