I bought a used 5.3 long block and was wondering if the stock computer will accept the newer engine ( currently a 4.8 ). My truck is a 1999 and the engine is from a 2001 model. My understanding is the only difference is the stroke, bore is the same. Thanks for any help.

 

Plug and play. Just drop it in and run it. Since you have it out, you really should put a little more aggressive cam in it. Changing the springs would be much easier right now. You could also have the heads milled to raise compression for more power.

 

it will work. bore and stroke are a little different. have your heads sheaved down .020. any farther and you'll have alignment probs w/ the manifold. the combustion chamber on those heads are 61.15. more power will be noticed. you should also get ls1 edit to do any tuning

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by sit n' low:
<strong> bore and stroke are a little different. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Bore is the same and stroke is alot different. Physically, it is the exact same block. Crank, rods, and pistons are different between the two.

One little interesting fact - to keep the 9.5: compression ration between the LM7 and the LR4, the 5.3 has dished pistons and the 4.8 have flat tops. Both are cast pistons.