I hate to do this because I'm sure there are alot more threads about this already, but I am new to the forum. I have a 2003 Silverado 1500 with a 5.3, and I want to build it to about 400hp. What are the possibilities of a four valve head being used on my engine? Should I replace my heads, or build my existing heads? Any other ideas on building the 5.3, without going too overboard with the whole $ aspect on things? I have a custom exhaust with MagnaFlow cats and mufflers, 2.5" the whole way back and an intake already. I would like to rebuild the engine and heads as well. So some internals are possible with my budget, I just want an idea of where to start, and an estimated cost. Thanks in advance guys.

 

How much of a budget are we talkin bout?

 

It's a cool idea for the 4 valve heads but I think it's more financially possible to build the heads that are on the motor just swap out cams to something more aggressive but your gonna need to change that exhaust to a 3 inch that's what I run on mine with a after market intake tube with stock air box ( I play in the mud a bunch and have learned that's better ) but I think the cams and the head rebuild port and polish will bump you close to the HP your looking for and a programmer would be a good investment these trucks are all computerized and you can adjust shift points with a programmer which you'll need to do with a any major head mod hope this helps like to know what you choose to do and how it goes good luck