If you buy the 4" crank kit with rods and pistons already balanced for you, the machine work should come up to somewhere in the $400-600 range to sonic test and bore the block over, magnaflux and test for cracks, hone the deck if necessary and machine wash everything afterwards. Your machine shop will need the pistons before he begins the block work so order the rotating assembly ahead of time to speed things up. The balanced stroker kit will probably be in the neighborhood of $1000 balanced, so be prepared to pony up. Try to hunt down a piston kit with your stroker crank and rods that fits the block. If sonic testing shows you cannot bore to 3.905, don't push it. A stock 99mm bore is plenty. If you end up with a 382, who cares it's still going to be a torque monster. Just because the old school Chevy 350's can be made into the legendary 383 doesn't mean your 4.8L has to be made into one. You'll blow the pants off it anyway. Always leave as much material in the block as possible.

Also keep in mind with your thin cylinder walls, you'll need to be sure of your cooling system since more heat will be transferred through the cylinder walls into the water jackets. The stock HD 35" radiator and '05+ fans would be a great addition to the build.

 

You might be able to get away with a 4.125" or even 4.25" stroke if the cylinder walls are long enough. With a 3.907" bore that would give 396 or 408cid.

 

ok, now what if i wanted to build a 350 out of it, what crank/bore combo would i need? also if i built a 383 like this would it hold up as a daily dirver?

 

I don't know how old you are or how far along you are with schooling or work, but someday I'm sure you'll find yourself in a real life situation or a classroom when the light bulb turns on about mass production. It's a simple economics idea that producing a good in large quantities to supply a growing demand will cut the costs of said good, which is AWESOME for us engine builders who want to buy an off-the-shelf stroker kit that many LS1 guys use. The 4" crank sold in 383 rotating assemblies is much more common than a 4.125-4.250" crank that some guys use for their big LsX blocks. The LS1 is a much more common motor, thus the parts for it are much less expensive. Yay for us!

To make a 4.8L into a 350cubic inch motor would mean you'll have to copy the original design of the LS1...kinda. The LS1 has it's 99mm bore and 92mm crankshaft (3.898"x3.622") which makes a 5.7L 346ci motor. You cannot bore a 4.8L out far enough past 3.905" to make a true 350ci motor, but really...what's another 4 cubic inches when you're talking about a complete overhaul of a motor? You'll need to buy a completely new rotating assembly, or find some LS1 guy who stroked his LS1 to a 383 and start there. You'll need new pistons, new rods and a new crankshaft for starters, of which you can probably find the rods and crank sold in the classified ads, but you'll need new pistons at least so your machine shop has something solid and concrete to measure before boring your block over. Instead of hunting down all these individual parts costing you no less than $500 with an additional cost of balancing the rotating assembly ($200 or more), why not find an off-the-shelf 383 rotating assembly that already has the crank, rods, pistons, bearings and everything balanced for right around $1000? The extra 36-37cubic inches will be worth the expense considering the longer stroke will add pure torque to your rear wheels from the longer throw. 382-383 kits are available from many of the vendors to the right >>>>>>>, check one or two of them out to get prices.

 

He originally asked what was the biggest you could build a 4.8L block to. It is possible to use a stroke longer than 4 inches in a production Gen3/4 block. It is even possible to really bore out that 4.8L block and put big 4.200" sleeves in if you really want to get crazy. But at that point, you might as well start with the LSX raceblock.

 

Not all of us live in Texas where oil fields are like money trees out in the back yard. Realistically a 382/383 is the most economical route for a guy wanting to keep and use his 4.8L block. Wouldn't you agree?

 

what did you decide to do that was my first thought to do with my 4.8 after i took it all out and took the rpms up a little too high and bent two valve but i decided on an ls1 until i finsh my lsx build good luck and let us know how it turned out

 

traded my 4.8 short block for a 6.0l block and working on getting some good internals and heads, till its finished im just going to work on making the truck look half *** decent