ok here it is
my friend bought my other friend's truck and wants to do a head/cam swap, problem is, performance heads are expensive so i suggested using a stock head from another engine but i dont really know which one to choose LQ4, lq9, 5.3....etc?
his truck is a 4.8 5 speed, the only mods were doing is heads/cam and headers.
so what would be a good head/cam combination and what would i expect??

 

i would personally go with an 862 casting, take it to the machine shop, get some hand porting/polishing, 5 angle valve job, and about 0.030 milled off, pickup yourself a good smaller cam ( 212/218 is nice ) and some good LT headers... and of course, a good tune. i would also suggest some larger marine 8.1 injectors, and a bigger/better fuel pump to avoid any problems.

all of that said, he could expect around 340-350+ rwhp, maybe higher.

i put down well over 300+ rwhp without any headwork, n/a. the 862's are stock casting for 4.8's. they would keep the compression where it need to be, and the milling would bump it up even more, around 10.3:1 or so... dont quote me exact on that compression, but it will be somewhere close.

heads from an lq4-lq9 will be too large for the 4.8, and drop the CR, thus loosing valuable power, especially low end, where the 4.8 needs it.


almost forgot a price list----

cam- $400
used heads- $~200
head work- $~700
headers- $400
Springs-$60
pushrods- $100
injectors- $~200
fuel pump-$ ?

fairly costly, but will make good, useable power for that motor.

 

thanx a lot for the nice write up bro, so you dont think i could could just find any stock heads from another gm engine that would work perfectly with the cam?

 

no, i dont. the smaller displacement is killer in this situation. the 5.3 runs almost the same configuration, and the 6.0 (317 heads) have larger runners, and will lower your compression... 243 heads are always an option.... but i dont know what they would gain over stock heads without any work to them??

i think patriot performance was selling 243 heads assembled for around $500, but i dont know the exact geometry and flow of that head.... you would still need to mill that head for a 4.8 though, to get the compression you need.

 

how are you going to make 350 or more?
i only made 330 at the wheels with the 5.3 and your expecting more with a 4.8

 

243's would have to be milled because their combustion chambers are larger as well.

 

maybe your head work sucked??

joshua's 5.3 H/C made close to 390....

i made right at 310 with just cam + bolt-ons... with some god headwork, another 30-40 hp shouldnt be a problem.

 

30-40 WILL be a problem with that small of a cam. The only way you'd pick up that much woudl be if you're running a 5k converter and a 230+ duration cam. You are not going to benefit that much from better heads.

 

i was just telling him what my local machine shop "master engine builder" told me. he almost gauranteed me that he could do headwork on my stockers (862's) and pull 30+ rwhp from them...i.e. 5 angle valve job, p&p, milling , etc...... maybe he lied? i am no genuis when it comes to which heads are better for what motor, as far as flow rate vs price vs real hp gains....

thats why i chose nitrous! its always the cheapest power.