I have a 4.8 that is apart now. I was going to swap in a 5.3 crank and rods but found out that the 4.8 has press fit pins and the 5.3 is floating. Now I don't know what to do. I have two blocks and can get a set of 5.7 ls1 pistons with 22,000 miles on them. I guess I am wondering if I should punch out one of these and build me a 5.7 or just bolt the 4.8 back together and run it.

The goal is around 350rwhp or as close as I can get anyways. It is going to get a cam, ls1 intake, and 1 3/4" or 1 7/8" headers depending on the cubic inches. This is all going in my 1976 vega wagon with either a 4l60e or a 200-4r. It is not a dd but will be driven a lot when the weather is nice. Thank you all for the input.

 

Gotta look at price : power ratio. Most people will say punch it to LS1 specs

 

The early 4.8L and 5.3L did have press fit pistons. It was somewhere around 2005 that the 4.8L and 5.3L went to a full floating piston. It looks like what you have is just a problem with the years of the parts not interchanging. If you were looking to rebuild it though, the 5.7L build will give you quite a bit more power over what you have right now. The machine work and balancing will be your only main expense.

 

no replacement for displacement!

 

Yeah that is my thought. I have the crank, rods, and the engine is already torn down. The pistons are cheap and I think I would really like the extra displacement. I will be replacing the bearings and all anyways since it is this far apart.

If I do this and still run the 862 heads, with a port and polish job, what will the compression be?

 

i just finished building my iron 5.7....i used the 862's but did a 3 angle valve job and put in ls1 intake valves...compression was 11.06:1

 

Cool thanks a lot.

 

no problem, good luck with the build