I am doing a 5.3L with a MS4 cam 239/242, .649"/.609", 111 LSA, LS6 intake, not sure what throttle body yet, stock bottom end, 46# injectors. I am going to run the Precision Race Components Spring Kit on either set of heads but i just wanted some input on what combo would work the best.

 

since nobody sees you I'll put in $.02

I'm assuming you are putting flattop pistons in? In that case I would personally hold out for some 243s or even 241s. I had a 6.0 block that I was going to do that with until I scored a whole LS6 engine.

If you are using the stock pistons you're screwed because any change from the 5.3 heads will lower your compression even more than it is (9.4 or so?)

Also that big rowdy cam would be better suited for alot bigger cubes and rectangle ports. No way would I run that in a 5.3

 

this is what i said before... but then again like i tell everyone that i work on their cars... i dont know what im talking about or doing...

 

Thats a monster in a 5.3L. Its possible, but its going to take some serious tuning. What car/truck is this going in (I am assuming an F body?)

To answer your question, the 317 heads (6.0) will lower the compression of a stock rotating assembly 5.3 to almost 8.5, great for FI, NA...not so much. I would wait and get a set of 5.3L heads milled, or a set of domed pistons for the 5.3, but that will cause P2V issues with that cam.

Lurk around the board, most of the people here are running 5.3s in various stated of mod. And keep in mind, the times posted for these engines are in 4800lb or heavier trucks, so if its going in an F body, well, you you do the math!!

 

I thought the 5.3s already had flattop pistons?

 

Yea, its going in a 95 Firebird. Im not worried about the tuning part of it, I can get it tuned. Ive made some calls, TSP says it can be done, with just the prc spring kit, and the right stall. Everybody else I talk to about doing this, laughs at me, and says the motor wont even turn over when im done with the build.

 

i run a 236/240 .615 112LSA cam in my 5.3...you'll be fine...a competent tuner won't have any trouble tuning it either. have fun

 

better put some rod bolts in that thing. it will like to spin to the moon. i bet its gonna sound nasty

its prolly gonna need at least a 4200 to 4500 stall

 

Thats the object!
Well, that, and Im determined to prove all the guys that told me I cant do it wrong now.

 

Oh, and TSP said it can be run with a 3600-4000 stall