Derek 357i

iTrader: (1)

Evaluating the feasibility of a destroked LS3 for an upcoming project. I have read all of the destroke literature out there and how they often fail to meet expectations.

Reasons for wanting to destroke:
Reducing torque output of engine to help with transaxle longevity
Transaxle already geared for "peaky engine" (think close ratio T56 w/ 4.88s)
Reduced displacement would help with fuel consumption at 2600 RPM @ 70 MPH
Quick revving engine would match the feeling of the engine being replaced
Sub 3000# car

Reasons against destroking:
Cost of building
Potentially better off with off the shelf LS6

Short block would be:
LS3 block
4.8L 3.2677" stroke crank (are these gun drilled from factory?)
6.560" H beam forged rods brand TBD
Mahle 4.065" bore 1.045" compression height pistons

Any thoughts on this?

gnx7

iTrader: (28)

what transaxle?

What tires?

Intended use?

redtan

iTrader: (5)

If you have the money to build a peaky engine (meaning high revs) then you will surely have the money to drop in a $150 crank. You're building the engine up anyway with pistons and rods, so the only extra cost of going with the 4.8L crank vs. the stock one is its cost, which is cheap.

For a sub #3000 car you won't really miss the torque, plus you have very tight gearing which will help make up for the loss of torque anyway not only through multiplication but by keeping you high in the RPM band at all times.

Derek 357i

iTrader: (1)

The transaxle would be the Porsche G96/00 RWD transmission. Tires would be either 295/30/18 or 315/30/18. The use would be primarily street, with occasional track days thrown in.

As for cost of build, it is going with a crate LS6 vs. the cost of a LS3 build from bare block, and the inevitable requirements creep that happens when you build.

91sonomast

Ok I have some questions on destroking a LSx, back in the days of the old V8's destroking was a fairly regular practice that happened with great success.
A friend in hs had a 377 which is a 400sbc with a 350 crank stock bore, that little motor would haul ***, he had a 10k rpm tach and it would bury the tach and still pull like a semi. The motor was in a 1985 2dr s10 blazer so the truck was fairly light. The engine had stock 350 crank, KB pistons, moderate cam, vortec heads, RPM intake manifold, and GM pink rods, which were a GM performance product and it stayed together. When my cousin tore it apart for a freshening up the rod and main bearings were rough and the #1 cylinder wall had some scarring but it wasn't bag enough to bore it. So it shows that the factory components would handle those kind of rev's, if he had aftermarket lighter rods and a forged crank I think the scarring and bearing problems wouldn't have been nearly as severe.
In the LSx world are there benefits to destroking one of these engines? People are making insane amounts of power with fast revving 454's. If his truck would have been a stock 400sbc I know it wouldn't have had the same kind of power, the fast revving destroked engine made that little truck. So, is it worthwhile destroking a LSx, and what would be the limitations and usefulness of doing it?
I hope this makes sense, if not ask some questions and I'll do my best to provide answers.