I have checked a local shops and actually was offered a 4.8/5.3 motor that has been bored .030.Is that close to a 5.7l?

 

Well the 4.8L bore= 3.779 x stroke= 3.268
The 5.3L bore= 3.779 x stroke= 3.622
You can bore it to 3.893. The 5.3L block should give you a 5.7L at that bore. The aluminum block cannot be bored over no more than .010.
At least that's what I have researched.
I don't really know what or how much that's over. It seems to me like it would be 0.114 over. Not sure if that's right, but looks like it.

Jim

 

Jim is right on. You can bore out the 4.8/5.3 block ( same for both, only stroke it different ) to 3.905" and use all the overbore 5.7L parts. Crank is identical on all engines except the 4.8L.
Boring the 5.3L out 0.030" is easy but finding pistons will be difficult and expensive. You will save money by boring out to the 3.893-3.905" range and using standard LS1 internals.
Plus you can then drop in a 4" stroke crank with no mods for a 383ci - 6.3L torque monster!

 

i just talked to the guy at the local shop and the motor has been bored from 3.77 to 3.809 on the iron block.Should i grab this and have him bore it larger or will this be ok for my ls1 heads and cam i just got.

 

I would go to a minimum of 3.898" and make sure they use torque blocks. The 3.809" is unusual and would require custom pistons. Again the custom stuff will cost way more than the extra bore work.
If you decide to go with a 4" stroker kit most of the pistons are for 3.905" bores. The companies assume there is some minor wear on the stock bores and this allows for a nice 0.007" hone which makes the rings seat better. Just keep in mind the final parts list, I went small my first time and had to pay for a second hone to get to the final 3.905" bore.

 

KTM how much did you have in your 383. I can find a 4.8/5.3l block aorund here pretty easy and cheap. I would love to build it to a 383. Would it be cheaper then a 6.0?

 

It is cheaper than buying a short block if you do most/all the build yourself. I got the motor for $300, wouldv'e spent $350 on the bore work, $2000 for the complete rotating assy ( crank, rods, bolts, pistons, rings, bearings ), $100 main line bore, $300 for gaskets and head bolts. I sold the #862 heads for $200 then bought and built some #241 heads for $800 total ( valve job, Z06 cam and springs, deck, minor port and polish ). So for the short block I spent about $3000, long block about $3600 ( after the head sale ). You can find the 402ci shorties for $3600 to $4000 depending on shipping and add ons. Having it built would have cost me $750 locally so going the no-dirty-fingernails route would have been a wash. Also remember you can use any 4.8/5.3 motor if you plan to stroke it.
In the end I had something unique that kept me away from the TV and a little pride of ownership. I would not mind doing it again but with the price of the 402/408 shorties so reasonable it could make the choices harder.