84Mercedesguy

instead of turbocharging it Im thinking about doing an N/A build on a 4.8 or would it be cheaper to build a 350
my goals are to get around 400-500rwhp

Jake89

You won't get the 4.8 near 500whp (not even sure 400whp will be that easy) without dumping a lot of money into it. Probably better to go with the 350 and build it. Plus the engine would already be out of the truck so messing around with it would be easier.

96capricemgr

iTrader: (1)

For your goal I would NOT use either a Gen 1 350(guessing since the 5.7 LS was not a 350) or a gen 3-4 4.8l. If you meant 5.7l LS variant then I would skip that too since they are overpriced, and lack updates later truck engines have as well as have heads you would probably want to outright replace anyway. For 400+rwhp NA I would look for an LQ9 and settle for a LQ4 is needbe.

Forcefed86

iTrader: (4)

Seems like a 4.8 could come pretty darn close... The "big bang" 4.8 had a mild cam, Fast intake, 102mmTB, ported stock heads/springs. Put down 451 chp (at 7k) and 380ftlb. That was with huge ring gaps on bone stock bottom end.

I'd think with a bigger cam, more compression, better intake, exhaust it could hit 400whp no problem.

The 6.0 short blocks are really rare and expensive these days. Looking at 3x the cost of a 5.3/4.8. (not worth it IMO)

Heres the na 4.8 dyno.

http://www.hotrod.com/how-to/engine/...g-bang-theory/

Same deal done on a 5.3... 503 hp at 6,600 rpm and 441 lb-ft of torque at 5,700 rpm.

http://www.trucktrend.com/how-to/eng...5-3l-big-bang/

DavidBoren

I think there's a lot of potential in a n/a 4.8L build.

Send the heads off to west coast racing for their stage 1.5 porting.

Get some 12:1 compression pistons.

Custom cam.

Holley hi-ram w/ 102mm throttle body.

Shift at 6k and enjoy.

alowerlevel

iTrader: (1)

Shift at 6k???? More like 8k

96capricemgr

iTrader: (1)

People talk about throwing pistons in a block as if it is free. IMO more people need to weight the cost of piston and related work vs. just spending a bit more on a nicer used engine.

Forcefed86

iTrader: (4)

8k isn’t gonna happen without serious money.

Fedmogul/speedpro hyper pistons are pretty darn cheap. If you do end up going with pistons. Have the block sonic checked and bore it as big as you can. No reason not to go with a 3.89” LS1 bore and cheapo hyper pistons. ($228 a set) Retain the 4.8 rods/crank. Additional cubes never hurt an NA build and 400hp isn’t going to stress the block a ton.

I see No reason to change pistons. Bump 1 CR point with a mill job on OEM haeds. Work the ports, slightly bigger valves, 3 angle valve job, gen4 high volume DOD oil pump.

Go as big as possible without PTV clearance issues on the CAM. Good springs, pushrods, rockers. Nice intake, exhaust, and a 7k red line. Will get damn close to 400whp if not more IMO. Hit it with a little nitrous if you want more.

I always wanted to try those $1200 ITB china setups on a little budget 4.8.

DavidBoren

I said to shift at 6k because it's the practical limit of most stick shift transmissions without spending big bucks.

Plus, shifting at 6k gives you 1000rpms before redline, so you can rod it out when you "need" to. But 7k rpms is the practical limit of the LS wet sump oiling system. Any sustained driving above 7k, and you are out running the motor's ability to keep itself lubricated, without big dollar dry sump oiling systems.

From a practical standpoint, the short stroke offers NO advantage other than reducing piston speed or improved rod ratio. The 4" and even 4.125" stroke cranks can still spin the LS platform to the limits of the wet sump oiling system.

That being said, I still think a high compression 4.8 would be worth every penny. Custom 12:1 forged pistons aren't THAT expensive.

The OP said that this is an engine build, not a swap. He intends to replace parts and BUILD this motor, so custom pistons aren't any more or less expensive, or difficult to install, than anything else involved in an engine build.

West coast cylinder head or Tony mamo heads if you have the coin.

Good cam (probably custom).

And a really good dyno tune.

Feed it premium gas or set it up for corn/flex fuel if they sell it near you.

And yes, one of those ITB set-ups would be awesome.

96capricemgr

iTrader: (1)

The OP is worried about budget, custom pistons to use the smallest displacement variant and Mamo heads is just absurd to even discuss. Even if one bored out the block the extra machining cost extra money.
I would at least start with a 5.3l if staying NA and I wouldn't screw around with pistons and crap, leave the bottomend alone and put money in heads and valvetrain. That is how you make power on a budget, you start with a factory shortblock and leave it the hell alone, spend the money where it makes a MUCH bigger difference.

Forcefed86

iTrader: (4)

I agree to a point. I like the idea of the 4.8 for its rev happy nature. I wasn’t considering a manual trans. With properly setup stall, gear, and auto trans… the loss of low end torque won’t really be noticed. While the ability to rev out to 7200 or so on a regular basis would be very beneficial. It will also allow cheaper converter to be used. The small converters that couple well at low RPM are roughly twice the cost of a good 10”.

Of course this is all straight line drag stuff I’m talking about. I forget that’s not every ones goal sometimes.

DavidBoren

The budget minded 4.8 n/a build would include WCCH stage two heads, $1100 if you exchange your cores, 1.8 rockers, L92 vvt cam, afm/dod delete kit, and zero deck the block for as much compression as you can manage without ptv clearance issues.

You can probably find a L92 vvt cam for the price of shipping. Retaining the vvt and deleting the afm/dod system is cheaper than swapping all your timing chain and gears and cover to the ls2 stuff. Most new rockers have upgraded trunion bearings, which is a must if you want to capitalize on the quick revving short stroke. Decking the block to give you some compression is a better choice over decking the heads, in my opinion. You want the head sealing surface as thick as possible, and I'm sure they are at least surfaced, if not decked to some degree, at west coast cylinder head. Plus, decking the block gives you a full bore reduction, rather than just reducing combustion chamber volume. Decking the block also provides you with a perfectly flat sealing surface with your freshly CNC'ed stage 2 heads. If you retain the vvt system, you have to be more aware of piston to valve clearance. But you have some room to work with. Without decking the heads or block, in oem configuration, you have room for the slp 1.85 ratio rockers and the stock L92 vvt cam. It's the only other factory cam with vvt that isn't a afm/dod cam. So it's the only factory cam you can use to retain vvt and delete the afm/dod system. It's a small, but noticeable, step up from the 4.8/5.3 cam, yet still gives you the 50 degrees of cam phasing available from GM, even with the 1.85 rockers. Most aftermarket vvt cams require a cam phaser limiter, that limits cam phasing to 20 degrees, to avoid ptv clearance issues.

Anyways, if you are concerned with budget, then absolutely spend as much as you can where it will make the most impact... The heads.

Plus, if you ever want to go bigger displacement later, a nice set of stage two ported cathedral port heads will still support any displacement possible on the 3.78" bore (or even the 3.89", for that matter)