243s are a bad choice for a 4.8, they have larger runners which slow down runner velocity and will hurt mileage when cruising, especially if they are ported. Along with the larger combustion chamber dropping your compresion netting worse part throttle response and and worse mileage.

For the effort and money put into a set of (ported)heads you could swap the motor and throw in a bit larger cam and net more power with better driveability.

Ive built or driven all kinds of combos and IMO if you stay NA you cant beat an LQ4 shortblock with a set of ported 243 heads and a mid 220s cam nets decent mileage(18mpg on the highway in an ecsb 4wd) and great manners.
Lance also has a regular cab with a 5.3 in it AND a 3600 converter to run the times he has. Totally different animal than the OP's setup.

 

if 243s are a bad choice, why r they coming on the nnbs 4.8s? and i would have them milled.020-.030 to bring CR up

 

The "243"s youre referring to are now 799s and GM went to the 799 heads for both the 4.8 and 5.3s for the NNBS trucks, and Im sure that was a change across the board for simplicity. The 799s have a 65ish CC combustion chamber whereas the 862s that are on the older 4.8s and 5.3s had ~62cc, the new 5.3s are sporting flat top pistons so the difference in combustino chamber size doesnt effect the 5.3s. They also benefit from a better flowing intake too(might be a worthwhile swap for more power).

Its going to cost you 60 bucks for headgaskets, 40 for headbolts and an absolute minimum of 100 bucks(more like 150+) to get the heads milled. So you're into it for minimum of 200 bucks for very minimal gain at all. IMO its not worth the effort.

The only way Id consider a head swap on a 4.8 is to something with SMALL runners and chambers. This bumps up your CR while keeping port velocity up. Something like the AFR 205s, DART 205s are economical in as cast form and are decent performers. The best bang for the buck would be a set of 862s from WCCH with their stage I setup and mill them to bump your CR up to mid 10s.

With that said Id save for the setup I mentioned in my previous post, and if youre budget minded skip the head swap for now and just run the 317s. If youve got money to spare a set of stock 243s will bump your CR nicely but even in the 6L case I still probably wouldnt bother swapping unless they had some work done.

If youre just looking for more sound then go for the 220 on a 112 atleast the 112lsa will bring the power down lower in the rpm band some.

 

He never really said he was after the world fastest cam only truck. That cam and a converter would be a ripping street machine.

 

i will eventually do a 6l swap, but im not anytime soon(2+ years). as for as sound goes, thats not y i wanna change cams, my truck is starting to feel slow to me, i know a bigger cam would net a little more power. as far as my heads, they are 706s, i know these have a little bit higher compression. prolly gonna go with tr220 112 with some PAC 1218s. Thanks for all of the input, im learning more and more about these motors. so bone stock 243s wont flow any better than my 706s do? Not trying to be difficult, just dont see how it would be a waste of money, i can get a set for 400-450

 

If you've got a 3000 converter your money with the TR220 cam, GET A 100 SHOT & YOU WILL LOVE LIFE! I would actually do that before you get a new cam. If your truck is feeling slow then thats what you want. PROMISE!!! so a 100 dry on the maf especailly with your injectors and ask Wheatley for a spray tune. If your not doing the cam for sound GO SPRAY!!!! First mod I did was a 100 shot and it dropped me for 16 sec 1/4 down to mid 14's...

 

Agreed a bigger converter would help with a bigger cam, I was worried about his trucks cruising manners since he mentioned long road trips. Houston to Dallas is 5 hours and gets into some decent hills. I personally cant stand lack of part throttle power.
243s flow better than 706/862s for sure. The problem is they have a larger intake runner and bigger combsution chambers. The larger intake runner slows down port velocity so when youre cruising down the highway and not turning 6K rpms the air doesnt rush into the comustion chamber as quickly and mix the air/fuel together as well therefore reducing low rpm efficiency(aka cruise rpm on the highway).

 

THIS!!!


Simple and sweet

 

oh helllll, now ur startin to sound like Wheatley!!!! he is forever tellin me to spray it. F*CK it, new cam, AND spray!!!!!!!!!!!! Oh Charlie.........i need a favor!!!!

 

Just food for thought.... The heads on my truck have bigger runners and valves than 243's, but my CR is in the low 10's... My Throttle response is NICE, my part throttle is great, ask anyone who has been in my truck it will rev damn quick, not to mention it is pretty quick compared to other 4.8s on this board, plus i get 22mpg on the highway.....

anyways, it is nothing compared to a 6L, but for what it is i can't complain...