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2004 Chevy Tahoe 2WD 5.3 Flex
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Discussion Starter #1
Looking for a little advice. I am 55 and new to auto mechanics. I never had time, room, or money, but now those issues are over. I am not rich but have some play money. I have a 5.3L that I kept after having a reman engine installed in my wife’s 2004 Tahoe. My initial plan is to rebuild it stock and have it ready for my 2007 Silverado (New Body) in a couple years. My Silverado LT is the 4.8L.

My desire is to rebuild an engine with an oversized cam, port my 243 or 799 (I have both) heads. Go with higher flow injectors, etc. I have no idea about HP but a nice round number is 500 HP. I would like burn out and feel myself pulled back in the seat. I don’t race but am guessing a 12 second car?

Is a 5.3L big enough? Do I bore it to 5.7? Or is it just as easy to find a scrapyard 6.0 for less than $1K?
Also I have no idea what I am going to put it into so I need advice on that as well. My dream car is a 68-74 Nova but that likely only a dream. So I may just need anything no matter the looks and yes cost and ease of installation is important. Like matching the transmission , etc is important. However I am also good with buying a used 4L60 or 6L80 if needed. I just don’t want to have to replace everything under the seats.

Any simple feedback appreciated. Please don’t go into complicated perfection tuning details. I just want to hear my project sound great and go fast.
 

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My 1st question would be in regard to engine condition
Why did you pull the 5 3?
 

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2004 Chevy Tahoe 2WD 5.3 Flex
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Discussion Starter #3
Initially my 5.3 blew a lifter at 250K miles. I dropped the oil pan and windage tray and found all but 1 of the roller pins. I removed the heads and pulled out camshaft to inspect and a couple lobes were severely worn (likely cause if my P0300 issues).
I was going to repair myself sending heads to shop and install new camshaft /lifters but I was not 100% sure where that last pin and maybe some smaller pieces from lifter went even though the engine turned over without noise. I was quoted $3K for a new motor installed and considering it also had a rear main seal leak and my wife needed her Tahoe back I just took the reman package. Now I have a 5.3 long block sitting on my first ever motor stand in corner of garage. It’s calling to me, but once I started thinking about what I wanted to do I am asking myself why not 6.0? I have watched lots of videos and do not think I ever want to get into the turbo world but just rather a camshaft, heads, headers. So for me it’s not winning a race I am after. Honestly I just eliminated the 5.7 boring because I don’t want to buy new pistons. So it’s a 5.3 or 6.0.
 

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You have me confused, how are you going to get a 5.3 to a 6.0 without boring?

And, the other thing that is confusing is your need for pistons if you go to 5.7 and you don't need pistons if you go to 6.0.

All 3 engines use the same stroke at 3.62, the difference in size is all bore related.

By the way, if the block is aluminum you shouldn't exceed 10 thousand with a re-bore.
 

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I assumed he was planning on picking up a junkyard 6.0 to rebuild but IDK, guess another old adage comes to mind now, assumptions are dangerous!
 

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2004 Chevy Tahoe 2WD 5.3 Flex
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Discussion Starter #7
Yes the boring was taking 5.3 to 5.7 but likely too costly for new pistons? Or can I get junkyard 6.0 for similar cost and just keep my 5.3. I see 6.0 junkyards costing $3K plus on eBay. Why so high?
 

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I assumed he was planning on picking up a junkyard 6.0 to rebuild but IDK, guess another old adage comes to mind now, assumptions are dangerous!
I was making the same assumption; but a junkyard 6.0 engine (cause no one will sell a junkyard block) compared to 8 positions, I don't think it's even close, but I've never priced them.

However, if the 5.3 is aluminum, and it probably is, you can't bore it out to a 5.7; so the piston cost is not an issue.
 

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2004 Chevy Tahoe 2WD 5.3 Flex
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Discussion Starter #10
My 5.3 is iron block. 2004 Tahoe LT Flex Fuel.
 

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2004 Avalanche 5.3 4WD. LM7 TSP 220R cam, PRC stage 2.5 243/799 Heads, LT headers, 6" lift 35s
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I feel like 500 horsepower is a hard number to get to on a 5.3. At least naturally aspirated anyways. Not impossible, but difficult. And I am not 100% positive on this but aren't the 243 heads the exact same head as the 799? I think they're labelled 243/799. You'll have to mill them .025 to keep compression or go to the flat top pistons from your 4.8. If I remember correctly they have the exact same bore as the dished 5.3 pistons. But theres a lot of options. I think 450hp is a more realistic number. A good cam, like the TSP 224r, those heads and pistons, 102mm tb, a good intake manifold, 42lb injectors, LT headers, and a good tune will get you there. You'll want to go to a 3000 stall TC while you're at it to get into your power. Bonus: the stock rotating assembly will handle all of this easily.
 

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2004 Chevy Tahoe 2WD 5.3 Flex
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Discussion Starter #13
Thanks Vegas good stuff.

For transmissions same question. Is it easier to upgrade my 4L60E or buy a junkyard 4L80? I have read that swapping to an 80 is not drop and swap and could require a new transmission crossmember, a new torque converter, a set of transmission lines, a modified harness, and a modified driveshaft with a larger yoke and crossover U-joint. However once that is done I probably could drop and swap junkyard 80’s as much as needed and they would support in upgrade to a 6.2 in future. Thoughts?
 

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2004 Avalanche 5.3 4WD. LM7 TSP 220R cam, PRC stage 2.5 243/799 Heads, LT headers, 6" lift 35s
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Thanks Vegas good stuff.

For transmissions same question. Is it easier to upgrade my 4L60E or buy a junkyard 4L80? I have read that swapping to an 80 is not drop and swap and could require a new transmission crossmember, a new torque converter, a set of transmission lines, a modified harness, and a modified driveshaft with a larger yoke and crossover U-joint. However once that is done I probably could drop and swap junkyard 80’s as much as needed and they would support in upgrade to a 6.2 in future. Thoughts?
It isnt a direct swap, you're correct about that, but I do think upgrading to and 80E is the way to go, because once you're putting down that kind of hp, that 10 bolt semi float rear end and 4L60E are going to be the weak links.
 

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2004 Chevy Tahoe 2WD 5.3 Flex
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Discussion Starter #15
Should I consider buying the oldest use car around that already has the 80 transmission and 6.x liter engine? Maybe I should just look for an old 2007 Camaro, etc? I want to rebuild a motor as part of the fun but need my learning curve on transmissions, driveshaft, differential, suspensions, etc jumped directly to the lowest cost option.
 
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