c6moneypit

I am thinking of using a stock ls3 crankshaft with new forged internals for an ls3 build to use with an a&a supercharger . The car is currently making 630 rwhp with methanol injection on stock internals (2013 grand sport with dry sump). I'm going to keep the power level about the same, building it so it can be reliable on hpde events. My questions: 1. Ls3 cranks are said to be good up to 800 rwhp... do you agree and should a stock ls3 crank be sufficient? 2. Are all ls3 cranks the same, or do certain models differ in the strength of the crank (are ls3 cranks from a camero vs a base vette vs a grand sport equal in hp capacity). I ask because the plan is to use an ls3 block and stock crank from a different car to build the motor then swap it into my car when it's done to minimize downtime. I will give then my block and crank as a core swap. I need to know if any ls3 crank will be good enough or if I should look for an ls3 crank from a specific car.

turbotuner20v

You need a grandsport crank... Needs to have a long nose for dry sump. The grandsport crank is the only 3.622" stroke crank that has a 6 bolt flywheel bolt pattern and long snout for dry sump.

c6moneypit

Awesome thanks for the info. So do you think I'll be good up to 700 rwhp with stock gs crank?

turbotuner20v

I made 937whp and the stock ls3/3.622" crank worked fine

c6moneypit

c6moneypit

so then for my next issue... If I get the shop to use an ls3 block as a core and build it so I don't have my car disassembled for 3 to 4 months (the engine builder is a bit backed up with orders), I'll have to locate a stock ls3 3.622" 6 bolt grand sport crank. The other option is to have the car in the shop for 4 months. I wonder how hard it is to find one and how expensive. I might just have to bite the bullet and give them the car and use my car's block and crank. It would save me money and be easier. The more expensive options would be to get an aftermarket crank for the gs ls3 with dry sump and have the shop build that setup up then drop the motor into the car, or just buy an engine pre-assembled.

old motorhead

Unless your tune is crap and/or your fuel is crap, a stock LS3 with meth should live a long time. I'd take my chances vs going through a complete engine build. After a few less than good experiences with "built" engines, I'd go with the stocker. If it broke, I'd replace it with another stock LS3. You're not living on the edge pushing a stock LS3 to 630rwhp....especially if you keep the rpm at a reasonable level. Just because you're sporting a built motor doesn't mean said motor is bullet proof.

c6moneypit

I have read of a lot of guys advising against building the motor and just replacing the stock motor when it goes due to bad build experiences. So you think running road courses on HPDE's with the stock motor on meth with quality fuel and tune should be good as long as I'm not bouncing it off the redline?

Corvettinator

It wasn't clear from your original post, but you know that dry sump Grand Sports have the LS3 with a forged crankshaft, right?

c6moneypit

Yeah I was pretty sure about gs having forged cranks I just wasn't sure is non gs ls3 s had them. It looks like if I decided to do a build I would have to use a gs dry sump crank anyway because of the size.

old motorhead

Absolutely. No way would I tear into a perfectly good running LS3 at your power levels.

TurboVic

This...^^^
i'm at 900rw on a stock longblock GS Ls3 with NO issues and lots of Mexico runs.

c6moneypit

Thanks for your input everyone. .. making me feel a lot more confident about running my setup as is :-)

boostaholic786

Now this is very true! Ever since Bryan and Sam told me you were on the stock long block, it just makes me grin at how amazing GM engineered these LS3's and how they can really handle extremely high horsepower levels, while also being a reliable street car/race car.

Unreal

If I was building a motor, I would just do a 4" crank anyways.

Blackonblacksls

I'm with you, I don't understand why everyone wants to build small short stroke motors here recently.

Unless you are turbo, the bigger the motor the better off you are, unless you build so big you start to have durability issues.

c6moneypit

So what would you guys suggest for an ls3 build with a centrifugal supercharger? I'm going to keep my ls3 block stock for now since the concensus is that it should hold up fine with its current setup. .. just want ideas for the future.

QKSLVRZ

If you're dealing with the same head and cam, all a longer stroke will do is lower the rpm the torque and hp peaks happen. If you then alter the final drive to compensate for the change in peak rpm, they put the same power to the ground. What'll be different will be HP lost to friction between the two, intake and header tuning differences, etc.

The goal is to pump all the air the heads will flow at the highest rpm you can afford to pay for. A longer stroke will decrease how high you have to go before you're limited by pumping losses.
This is why in displacement limited classes where money is no object, they all evolve to big bore 4 valve heads, with a short stroke, and where allowed pneumatic valves.