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4.8 build

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Old 07-15-2012, 02:53 AM   #1
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Default 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!
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Old 07-15-2012, 03:01 AM   #2
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Correction its a demon carb
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Old 07-15-2012, 10:49 AM   #3
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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..


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Old 07-15-2012, 11:14 AM   #4
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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
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Old 07-15-2012, 11:21 AM   #5
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Originally Posted by lsthirdgen View Post
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..
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Old 07-15-2012, 12:17 PM   #6
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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.
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Old 07-15-2012, 12:58 PM   #7
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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.
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Old 07-15-2012, 01:12 PM   #8
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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!
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Old 07-15-2012, 02:52 PM   #9
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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.
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Old 07-15-2012, 04:52 PM   #10
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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
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Old 07-15-2012, 06:44 PM   #11
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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.
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Old 07-15-2012, 07:50 PM   #12
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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!
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Old 07-15-2012, 08:33 PM   #13
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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.
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Old 07-15-2012, 09:06 PM   #14
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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!
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Old 07-16-2012, 12:15 PM   #15
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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!
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Old 07-16-2012, 03:06 PM   #16
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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.
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Old 07-16-2012, 03:15 PM   #17
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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
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Old 07-16-2012, 04:14 PM   #18
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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!
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Old 07-16-2012, 05:26 PM   #19
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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.
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Old 07-16-2012, 05:52 PM   #20
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Yeah I'm just figuring out my options and pricing stuff out right now. Add that to my list to research.lol
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