Surewhynot

iTrader: (1)

Good afternoon everyone,

I'm planning a new engine for my 6 speed g body. I have two blocks I can use, either an ls3 block that I would do forged rods and pistons with a billet 7875 or a darton sleeved ls3 that is ready to be a 427. The car is mainly a street car, I do power tour and daily it in the summer. I'm looking to one day get back into auto cross. Car made 500 who with the current engine, but I'm looking for more power. Which would you build?

WE TODD DID

iTrader: (2)

More cubes will make more power, and the darton sleeved block will be stronger.

Surewhynot

iTrader: (1)

I just realized my post was confusing, what I'm driving at is turbo ls3 vs na 427

QwkTrip

iTrader: (23)

When you say more power....

* If you're generally happy with your engine but wish it had some more umph and throttle snap, then the 427 is that engine. The change isn't going to blow you away though. It'll be more like, "Now that's the way I wish my last engine performed!"

* If you want a lot more power and trap speed, then the turbo hands down.

ddnspider

iTrader: (26)

1) a 7875 is small for an LS3. You will have monster torque down low but it will run out of steam up top. It won't be as snappy as an NA 427 though. You can always upgrade turbos if you want more power. Just depends on where you want a powerband. Either way it'll destroy tires.
2) assuming you want north of 500whp, a turbo ls3 will have better street manners than an NA 427. Depends on if you care about drivability.
3) the ceiling on a turbo LS3 is much higher than an NA 427 and cheaper to boot.

Surewhynot

iTrader: (1)

The driveability of a turbo ls3 and the growth potential has me leaning that way.

Hmmm, what size turbo would you run then. I was told I could push the 7875 to around 1000hp before it ran out of breath?

Thank you

ddnspider

iTrader: (26)

I think 1000hp on a single 7875 with that many cubes would be very difficult. Maybe small cubes on an import at a high pressure ratio or running twins would certainly do it. Is 1000hp your goal? For a single and 1000hp I'd probably look more at an 82mm or 88mm from VSR or a Borg Warner S475 series turbo.

Surewhynot

iTrader: (1)

No, not looking for 1000, that was just the figure in was given. Looking for around 700 hp on street trim and 800 on kill. Honestly, that's probably pushing it on a g body frame.

ddnspider

iTrader: (26)

That is doable with a 7875 and will have killer low-end torque.

Surewhynot

iTrader: (1)

Thank you.

The complete setup will be an ls3 with texas speed cnc ported ls3 factory cast heads, approximately 10:1 compression with summit rods and pistons, Texas speed cam controlled by a holley terminator x max. Trans is a tremec magnum with a ford 9". The top end listed when on the l76 made 500whp/475 ft/lbs.

ddnspider

iTrader: (26)

Depending on whether or not you'll be pump or E85, you might consider a water/meth injection kit. It's cheap insurance.

Surewhynot

iTrader: (1)

93 and meth is the plan. E85 is rare around here (Buffalo, NY) and would make power tour a little more difficult.

Jimbo1367

I’d run the sleeved block regardless if it’s NA or turbo. Longer and stronger sleeves make it a no- brained. You just need to be realistic w yourself on ur goals.

BCNUL8R

iTrader: (2)

No need for a sleeved block for his 700 rwhp goal or anything under 1000 rwhp for that matter.

He will probably make over 700 rwhp on accident with a stock ls3 block and turbo.

Jimbo1367

I believe the OP stated he had these blocks all ready.