texas99Z28

I recently had my 1999 z28 dynoed. It is pushing only 300 hp to the rear wheels. It has a 4L60E tranny. I thought these LS1's were under-rated at 315hp? Why is mine sooo weak? Please help!

texas99Z28

Were the motors with auto trannies less hp?

bballr4567

iTrader: (5)

Take into account that you are suppose to lose about 18% of the HP rating with the Auto.

Cruz28

Someone else can probably go into more detail than me, and I'm sure they will, but for 99 they are underated at 305 at the fly wheel, where it's more like 345 in reality. So if your car is stock, 300 is a good number to the rear wheels.

shaZZam

iTrader: (12)

You are confusing Rear Wheel Horse Power with flywheel horsepower. 300 is perfectly acceptable on an automatic car with no mods, means about 340-350 at the motor.

ImStock

yeah for a stock LS1 to the wheels 290-300 is not a bad thing...

JD_AMG

Your car is rated at 315hp at the flywheel (like all cars), and is really making ~345hp give or take. Like already stated you loose 15-20% of the power though the drivetrain, so 300RWHP = 345 flywheel hp.

texas99Z28

Thank ya'll, i was really depressed about this!

texas99Z28

I'm thinking of putting SLP Loudmouth on it and 3.73 gears next. Good idea?

texas99Z28

My nephews 2002 Formula pushed 376 rwhp with a k@n filter and Lm exhaust, so I was hoping for 330 to 340 hp

qwik_ss

iTrader: (9)

is that on the engine or the wheels?

Prerun4fun13

iTrader: (6)

you wont gain 30-40 hp with just a cat back and K&N filter

BYE RICE

iTrader: (2)

Aftermarket lid, A catback exhaust..A Magnaflow is a good choice.It's a very nice looking exhaust & doesn't sound dirt bag-ish.
The first REAL performance mod to an automatic-equipped LS1 should be a torque converter & aux trans cooler...The converter will need some adjustments made to the PCM..So go ahead & find a good tuner ahead of time...Unless you are running 2.73's,gears aren't as much of a priority.

There are sponsors to the right who can assist you further.
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I'm a big Thunderracing /Texas speed fan.

'Trust'

iTrader: (24)

Lol, nope, it definitely didn't without bolt-ons and a cam.

bowtieblue1926

Yeah there is no way any f-body will hit 376 "at the wheels" with just a filter and a catback. My 02 firehawk isnt even at 376 rwhp. He must of lied to you or he has some additional mods done to get it up there. Not trying to come across rude or anything but from owning several f-bodys, vettes, thats impossible with just a catback and a filter.

bmxer8699

iTrader: (16)

numbers arent everything, remember that. you will lose power with a new stall i guarantee it, so dont freak out when you dyno it and end up losing alot of "numbers"