hey i got a stock 5.3l (2004) lm7 engine given to me yesterday, anyways i have a 2000 gmc with a 4.8 l and I'm goingto build the 5.3l id like to see a honest 375 hp at the wheels, i believe it has 706 heads on it, should i mod these heads? what spring should i use? what cam? what pistons?intake? i'm really on the fence here since I've read soo many forums! anyways any help is appreciated!!!!!

 

wereto start humm id go with sum 243s worked on and milled to 58cc and get a hold of a nbs intake its the best bang for your buck also sum dual springs 7.4 pushrods and a custom cam we call roadkill trust me we made one with this exact setup and made 398 to the rear wheel and hold the record for fastest 5.3 na with a 12.1

 

I would like more info on that cam, how much, and were to get it etc.

 

Don't mess with the 706 heads... they are known for being bad castings. They will crack and let coolant into the oil. I just changed my 706's for some 243's.

 

I'd maybe look into the stage 2.5 heads from TSP. Bigger valves (1.89 to 2.02 intake and 1.55. to 1.575 exhaust iirc), comes loaded with dual springs that max at .650 (you can get different ones if you need/want them).

They say it flows 15 CFM more than other similar (competitor) heads, and they bring your CR to 10.75. You could get them milled a bit for even more, but I think 10.75 CR, tuned to run 91 oct, throw in a mild cam, you'd be up around your 375 I believe... someone correct me if I'm wrong.