Carbureted LSX forum - 4.8 build

i just picked up a 4.8 long block today and plan on using the performer rpm carb kit on it and want to run my plan past some people more knowledgeable than myself. it has the 706 heads which i plan to mildly port myself and planned on putting in a 5.3 crank and Texas speed 228r cam. also found a nice 850 dominator that i might pick up but im not sure if its too big or not. my main questions are the carb size and whether or not the crank will swap as is or do i need 5.3 rods as well? thanks!

Correction its a demon carb

If your going to go thru all that work you might as well sell the 4.8 and grab a 5.3.. I bought my 5.3 for $285.. If im not mistaken you need to change the crank rods and the possibly the pistons.. I'm not trying to pee on your parade im trying to give you the best financial solution... 4.8s can be good runners too! My 2007 2wd Silverado WT Weighs 4900lbs w me in it and with a cold air intake and straight pipe it runs 15.16 @ 88mph.. 4.8s just need a steeper gear than the 5.3s to get moving but they certainly are screamers!!

By the way.. DO NOT GET the Edelbrock Intake/ignition kit.. its overpriced, and the timing pills suck... Its cheaper to buy the MSD 6010 and RPM intake separately...for both I paid $490 vs $700 and if your interested PM me and Ill tell you where I bought them new for that price..


Doug

what kind of power do you think i could expect out of my combo mentioned above if i just left the bottom end as is? also is the 850 too big for that set up? thanks

what kind of power do you think i could expect out of my combo mentioned above if i just left the bottom end as is? also is the 850 too big for that set up? thanks

An 850 is WAYY too big... a 600cfm carb will be perfect for your swap.. What kind of car is the motor going into??

Im not sure how much power you'd be making with that cam A rough guess would be around 340-350hp... the 4.8 and 5.3 can be close in regards to hp.. but the 4.8 has to rev higher to make those numbers and the 5.3 will always make more torque.. but judging by your Username if the 4.8 is replacing a tired old 305 it will def. put a grin on your face..

I am swapping a 4.8 into a 91 RS soon, will be a manual. Yours, if you port the heads and use that cam and just stock with 4.8 cubes, you can expect to reach 380 or more HP at the flywheel, 350 minimal, but it should do that with a zo6 cam, muck less the 228. Cannot wait to throw mine together. A build thread to come.

mine is gong in an 87 camaro with a built 700r4 and 3.42s. i plan on an appropriate stall at the time of the swap. i already have a carbed old school 350 in there. as it sits now with a 600 holley intake cam and headers i do around a 14.0 quarter, its not a drag car but i just like to run it every once in a while. i think i may look for a stock 5.3 crank and rods for cheap to get lil more compression. i was really hoping to get aroung 450 hp out of this.

mine is gong in an 87 camaro with a built 700r4 and 3.42s. i plan on an appropriate stall at the time of the swap. i already have a carbed old school 350 in there. as it sits now with a 600 holley intake cam and headers i do around a 14.0 quarter, its not a drag car but i just like to run it every once in a while. i think i may look for a stock 5.3 crank and rods for cheap to get lil more compression. i was really hoping to get aroung 450 hp out of this.

450hp is obtainable however you really have to scream it to get there.. and with screaming rpms comes compromising durability.. chose your parts arsenal wisely good sir! :)

450hp is obtainable however you really have to scream it to get there.. and with screaming rpms comes compromising durability.. chose your parts arsenal wisely good sir! :)

what do you consider screaming? lol. im most likely going to keep with a stock bottom end with my own head work because the heads that i have were recently redone i just plan to smooth them out a lil. is there a better cam choice i should be looking at? sorry for all the questions but this is my first ls motor.

what do you consider screaming? lol. im most likely going to keep with a stock bottom end with my own head work because the heads that i have were recently redone i just plan to smooth them out a lil. is there a better cam choice i should be looking at? sorry for all the questions but this is my first ls motor.

If I was to make an educated guess i'd say your redline would be around 7200rpm.. I could be wrong

At 7200 with a real set of ported heads, small chamber heads, like stockers milled, 2 inch primary headers, a cam in the high 240s, .600 lift, 110 lsa, spinning to 7800, that might make 450.

Do you mean I should mill the stock heads even if I put 5.3 stuff in it or is that just if I leave it 4.8? I would think with the 5.3 crank and rods and the 4.8 flat top pistons that might be too much for pump gas? thanks for all the info guys its a huge help!

That is what allot of people do, in fact, the 07 up 5.3 has the 4.8 flat tops. Will make more torque an hp. Milling will make more power.

cool thanks for the info. i think ive heard somewhere that the 4.8/5.3 block can be bored to take ls1 pistons, is this correct? if so do the crank and rods from the ls1 fit also? thanks again!

So I looked aground and it seems the 5.3 and ls1 both have the same stroke and rod length, just the bore is different. I forget the exact numbers but it looked like the 4.8 block could also be bored to take the ls1 pistons to basically make an iron block ls1. Has anyone done this? Or am wrong that this is even possible? Thanks!

Yeah, the iron truck block ls1 is a well-known replacement for the original aluminum ls1. Do a search for "iron ls1" and you'll find all the info you need to go that route.

Alot of guys build the iron ls1 for boost/nitrous for obvious reasons, the iron block is stronger and its cheaper.

I've got brand new je pistols and eagle h beam rods to do such a thing that I would be interested in selling. I bought them at the time when there was a big change to ls2 and l92 and went that route instead. Everything is still in the boxes. PM me if your interested
Beaudacious

Right on thanks everyone. I have some thinking to do now. I'm gonna look the block over after work and compare my options to my budget. I'm sure I'll have more questions as the build progresses. Great info on this site by the way!

For the cost of machine work and parts you would be way ahead getting a ly6 out of a 07-up 2500hd. With a fairly mild cam it should make over 400 to the wheels.

Yeah I'm just figuring out my options and pricing stuff out right now. Add that to my list to research.lol

For a budget, a set of stock LS1 pistons can be had cheap, ARP bolts for the Ross after swapping and resizing the rods, balance the assembly and then slap some stock ls1 heads on with a cam and you will have a fairly cheap investment in 400 rwhp.

Or scavenge a 6.0 and cam it and drive it like I did.

For a budget, a set of stock LS1 pistons can be had cheap, ARP bolts for the Ross after swapping and resizing the rods, balance the assembly and then slap some stock ls1 heads on with a cam and you will have a fairly cheap investment in 400 rwhp.

Or scavenge a 6.0 and cam it and drive it like I did.

do you mean for the ls1 pistons and rods to go on the 4.8 crank? i think im only going to go ls1 pistons if the block needs bored, not sure though. i also thought about just putting a 5.3 crank in with the 4.8 rods and pistons i already have but im not sure if the 4.8 rods are too long for this or not. i live in SD so the truck parts should be cheap and plentiful and if i can stay out of the machine shop as much as possible i should be able to save quite a bit. im still up in the air on most of this stuff though, just trying to get what i want and keep both of my arms and legs.lol

4.8 rods only work with 4,8 crank. Think a 4.8 bored to 3.905 ls1 piston makes 310 cubes. You can get a ls1 rotating assembly and not have to balance it. Just bore the block. Tge 4.8 can scream rpm. Just will not produce the torque of a larger engine.

I bought a 5500 mile lq4 short block for $500.00 off Craigslist. If I was you, I would look for a 6.0 shortblock and put your 4.8 parts on it. I think you would be better off in the end. Just my .02.

Exactly.

No replacement for displacement

So with that 310 cube set up how fast do you suppose I'd have to spin it to make decent power? I'm not really looking for a torque monster and the 310 seems different from the norm which appeals to me. Idk maybe its a bad idea but I like to new Lil different. Man i wasn't expecting this many options! Lol

To add to your confusion. I just completed a 4.8 swap into an 87 Monte LS. The 4.8 is a great motor I picked it off of CL for 100 bucks. I would suggest just throwing the motor in the car and driving it as is. Then you can collect parts to build up a nice 6.0 while you enjoy your car.

Just run the 4.8, I you don't like it change it up. You will be surprised by the power it will make with a cam, spinning 7000 will make decet power.

mike over at s-k speed hooked me up with msd 6ls2 and edelbrock intake, great person to deal with!

i just picked up a 4.8 long block today and plan on using the performer rpm carb kit on it and want to run my plan past some people more knowledgeable than myself. it has the 706 heads which i plan to mildly port myself and planned on putting in a 5.3 crank and Texas speed 228r cam. also found a nice 850 dominator that i might pick up but im not sure if its too big or not. my main questions are the carb size and whether or not the crank will swap as is or do i need 5.3 rods as well? thanks!

i agree with Zone89rs. i had a box stock 4.8 in my 96 s10 before i swapped to 5.3. when i first built it , pulled out on the road in front of my shop started burnout shifted second,shifted third(th350) sat there for another 5 seconds then let off the brake and pushed the throttle to the floor and proceeded to lay down over 450 feet of posi marks(monte carlo gov-lock in factory housing).I'd like to also mention this was with 26X11.5X16 M/T et street tires. I didnt have a tach hooked up at the time but she was revving and that little 4.8 was making power.
Beaudacious

thats not a bad idea either. it will certainly cut down on my parts scavenging time. at this point all ive done is tare it down and deglaze the cylinders so its wide open. im going from the bottom up with it so im in the process of finding the proper oil pan for the swap and then it'll be off to the machine shop for new cam bearings.i think the crank i have (if i use it) needs some work also. i will post as i go, thanks everyone!

Yep, slapping the 4.8 into my 91 RS I am getting Friday, then I'll can it and all the BS later.

Yep, slapping the 4.8 into my 91 RS I am getting Friday, then I'll can it and all the BS later.

awesome let me know how it goes!

I will, will be fun to see how it runs with the tiny 4.8 with a carb conversion compared to the L98 350 that was in the 89 once upon a time, went 13.87 at 101 mph with a 1.87 60 foot. Was a 5 speed with 4.10, will be a 6 speed with 3.42, so it will be held back by a bit of weigh difference and not as much gear, but I think it may beat that, or it may not. The l98 started at 235 hp, the 4.8 270, but the tpi was a torqy fellow with 340 ftlbs or so, but the 4.8 has 285, so it will be interesting. I would not me surprised if it did not beat the 350, simply make torque, but if it does....it will be funny to see the SBC lovers get upset when I give them a hard time. I could port the heads and put a ls6 cam in, but that would be cheating. Then again, we are comparing a car engine to a truck engine, so it is not exactly a TBI 5.7 it is going against, time will tell.

yeah im hoping to to get deep into the 13s at least with this. regardless of what i decide to do with the displacment on this build i will be putting an agressive cam in and porting the heads myself. on a side note id like to post pics in this thread of my car and maybe of the motor as it comes together but i cant figure out how to get them from my album to here. what am i doing wrong? i searched and everything.lol

I use photobucket.com, then it gives you the ability to post the code than links the picture here. Ported heads and cam will be 12s I'm sure with the right gearing and converter, as long as it isn't over 3500 pounds going down the track.

There is now way I would tear into a 4.8 and start swapping cranks and rod etc. The cost and potential problems would just be way too much for what your stated goals are.

I would either run the 4.8 for what it is or sell it and get a 5.3 or 6.0. That is the beauty of these motors for guys on a budget. Just pick up a good used motor, throw in a cam, springs, pushrods and a timing chain and they make awesome, reliable power.

Meh, I skip the timing chain part some times...lol

if i can come across a 5.3 crank and rods cheap enough i will go that route, if not it'll stay a4.8. either way its getting new bearings cuz they're cheap. the 4.8 crank has some wear on it but nothing i feel is too serious. i'll probly just smooth it out with emery cloth if i use it. and thanks for the photo help, here is the future home of my first ls motor.

http://s1245.photobucket.com/albums/gg590/lsthirdgen/?action=view&current=tint.jpg

if i can come across a 5.3 crank and rods cheap enough i will go that route, if not it'll stay a 4.8

If you do that, you will likely have to have it balanced at a machine shop as I would bet that the 5.3 rods and pistons have different rotating weights than the 4.8 stuff.

I will research it first but I don't think so. the pistons are the same and the crank and rods will be a matched set so I think it'll be ok. thanks for the heads up though, I'll look into it for sure

You should be able to select the bottom link for sharing, then it will post the pic here.

I will research it first but I don't think so. the pistons are the same and the crank and rods will be a matched set so I think it'll be ok. thanks for the heads up though, I'll look into it for sure

5.3= 3.78 bore. 3.622stroke. 6.098 c.rod
4.8= 3.78 bore. 3.268stroke. 6.276 c.rod
The balace will be different as the piston is different type dish vs. Flat.
And the rods have a significant difference in size. The 4.8 rods are heavier.
Compression height is the same for both.pistons. Take it to a machine shop or get it assembled by an engine builder.
The heads are sufficient, you will hurt performance more by hogging them out. If anything just leave the 706 alone and find a set of 243/799.
Mill them some and pay for a matched custom grind. This will more than likely net the best results.
Trying to make an iron ls1 is a waste.of time imo. Ive been there.
It will require -.120 minimum of metal to be removed from the cylinders. Bore and then hone. And balance of crank for new ls1 size rotating assembly.
You are ci ahead by finding a 6.0. And less hassle. Apply your cash to a 6.0 based build.
Or just run the 4.8 as is, til gather funds for bigger motor.

I thought the 07 and up 5.3 pistons were the same flat top design? if so I would think if I got a crank and rods out of a 5.3 all should match up fine since the crank and rods are a matched set with the same piston. Unless I'm missing something?

Im interested in how ths turns out. I have a good 4.8 in the garage Ive thought of building like this.

I will be doing cam only in my 91 RS, but the spare 4.8 for the future s10 will be ported ls1 castings and spin 7800 or so. I think a 4.8 will be fun, just need to spin them. Just get a 5.3 if you just deem needing the cubes just because it would be money saving to just run the engine that started as a 5.3.

Idk if I "need" the cubes but they would be nice. But like I said I'm only going that route if I come across the parts cheap. As you can see I'm kind of indecisive lol.I am however leaning toward going 4.8 just for simplicity as long as I can get what I want out of it. Thanks for all the help everyone!

http://i1245.photobucket.com/albums/gg590/lsthirdgen/tint.jpg

HA! it worked. thanks!

There ya go, nice ride btw. Got any more pics? Looks way better than the RS I just got.

Idk if I "need" the cubes but they would be nice. But like I said I'm only going that route if I come across the parts cheap. As you can see I'm kind of indecisive lol.I am however leaning toward going 4.8 just for simplicity as long as I can get what I want out of it. Thanks for all the help everyone!

Im a big fan of 4.8s.
My dd 4.8 has 349k miles. On stock longblock. They are very reliable engines and can take alot of abuse. If maintained.
As a matter of fact.
I have 09 4.8 with studs,ls9 gaskets,317 heads on a stand waiting.
I plan on running 20psi thru it on pump gas with a turbo.
Just looking for 3rd gen to drop it into.

http://i1245.photobucket.com/albums/gg590/lsthirdgen/clintspokerrun2011.jpg

http://i1245.photobucket.com/albums/gg590/lsthirdgen/camaro.jpg

hmmm not sure why the one is small but here ya go. do you have pics of the rs up anywhere?

The new one is in the new post, i think you may have seen by now, i have not checked that post yet.

Nice BTW, what wheels you have planned in the future?

Nice BTW, what wheels you have planned in the future?

im not really sure. ill probly just keep an eye out for something i can pick up cheap. id like a set of 18s. whatever i find will get painted black for sure though,just not rattle can this time.lol

I like the yellow with black wheels look. I think some 18" gunmetal z06 wheels would look sick with a little lower stance.

I like the yellow with black wheels look. I think some 18" gunmetal z06 wheels would look sick with a little lower stance.

i love the look of z06 wheels on these cars but im just not willing to run 2 inch wheel spacers :(

I understand that. Hot Rod has a third gen coming out in next month's issue that has gunmetal z06's. Its freaking awesome looking

Yeah I guess some guys swap in 4th gen rears just to run the wheels but that still leaves spacers or really expensive suspension overhaul as the only options for the front

Spacer no, adapters, yes, very reliable, made from billet, usually 150 for two.

Spacer no, adapters, yes, very reliable, made from billet, usually 150 for two.

i guess i just dont trust having the wheels spaced out that far. ive always heard it wasnt that safe, especially in a performance aplication. maybe its not as bad as ive heard though?

On thirdgen.org, they do it all day. The rear in my RS was from a 4th gen with third gen spacing. They ran adapter for the 4th gen wheels, 500 rear wheel horse post did not cause issues on the street, so on the front at the track they would be fine.

might have to give that a shot. vette wheels look pretty slick on third gens and ive run across a few over the years that could have be had very reasonably had i gone this route. no matter now, this build and swap will take most of my spare cash for a while lol.

well in my search for parts i found what is supposed to be a complete high milage 5.3 for $150. i guess it has a bad cam. the guy is having the motor swaped for a junkyard pull out. im not holding my breath on the crank being usable but its supposed to have coil packs and a bunch of other stuff that was going to nickle and dime me. hopfully ill have it this weekend

Hold your breath longer, seen complete 5.3 go for 200, I get them for 400$.

its supposed to be complete but the guy isnt sure what hes getting on the other motor. i should get everything minus the accessories. im only buying it if its all there

Sounds good.

so i drove my truck 60ish miles to get this $150 5.3 and end up leaving empty handed. guy said the shop that was doing the swap was gonna be open late friday so i could get it, i get there and the shop is locked up... what a douche!

Ouch, sorry to hear man.

does anyone have any suggestions on a cam? ive decided to just keep it a 4.8. im planning on putting a turbo on later down the road but it will be NA for at least a year or two after the swap while i gather parts. i want something thats going to sound good and run hard in both NA mode and with the turbo. idk if it matters but i dont plan on much boost, at least not initially. thanks