substitute 4.8 in place of 5.3?

Long unnecessary back story: I traded for a 2000 Tahoe with 170k on it. Looks nice. Has almost every option. But among the service records I find that it's been brought in twice in the past year for being really low on coolant, both times no leak has been found. Ran great when I got it. Quiet too. Oil looked disgusting. The first time i changed it, the stuff was still coming out in globs 20 minutes later. eventually I pulled the pan and scooped out all the poop, cleaned the pickup, etc. After that the engine has always sounded like crap when I first start it, and has a noisy lifter that doesnt go away. Now I'm nervous to sell it. Ive been considering just swapping in another motor, which leads into my question...

5.3's have gone up in price around my city. Higher mileage ones now trade for 3-400 more than lower mileage 4.8's. How much extra effort would it be to substitute the smaller engine in a 2000 Tahoe?

Direct bolt in, not sure about the programming on the ecu. I also have a couple of 5.3's in my shop with @100k miles I'd swap for 4.8s if you would rather take out the uncertainty, and I could meet you in Sioux City.

For most of what I would use the engine in the 4.8 is a better bet.

I've driven both, in trucks, and the difference in power was noticeable, moreso in a heavier SUV I'm sure.

The 4.8 sucks arse in a 4x4.

What casting number are the heads? (You should be able to see the number on the passenger side head, driver's side would be against the firewall) Some casting number 5.3 heads are known to have porosity issues, they seep coolant through the aluminum near one of the oil drainbacks.

When you re-installed the pickup, did you use the correct O-ring? There are three different sizes. A too-small O-ring will cause the exact symptoms you've got since the oil pump will be sucking air. Maybe make 20psi at idle if you're lucky.

It's a bolt in.

How's your oil pressure? You may have low oil pressure due to a broken o ring in the pickup tube.

Lifters are a weak point in these engines, and you have to pull the heads to replace them.

Programming of the ECU is easy enough, but, you need software to do it, or you need someone to do it for you. This may add some additional cost. Do you have a friend with HP Tuners or other tuning software? If not, count on 250-500 at a minimum.

Knurled wrote: Some casting number 5.3 heads are known to have porosity issues, they seep coolant through the aluminum near one of the oil drainbacks.

The official(probably) fix for this are the bars leaks tablets you can get from most parts stores.

Also look at the oil pump bypass valve, they sometimes act up on 5.3s, my dad lost one to that on the highway not half an hour after buying it, lost pressure, gained it with a switch to neutral and a throttle blip, then lost it again a minute later and grenaded.

Kenny_McCormic wrote:

Knurled wrote: Some casting number 5.3 heads are known to have porosity issues, they seep coolant through the aluminum near one of the oil drainbacks.

The official(probably) fix for this are the bars leaks tablets you can get from most parts stores.

I remember seeing somewhere (AERA bulletin?) that "the" fix involved cleaning the area very well and applying some magic epoxy. Could be done with engine in-chassis, access through valve cover.

Me, I figure that the problem is limited to certain model years and a single foundry, so THE fix is to yank the heads off and install heads from outside the failure window.

*I make this guess based on how GM had those bars leaks tabs developed for the 90s aluminum block Cadillac motors that had so many porosity issues it was considered routine maintenance to stop leak em.

It has 706 heads on it. I wondered if theyve caused the sludge buildup problem over time by introducing dexcool either from being porous, or cracked.

I used a new o-ring on the oil pickup tube. Pressure as indicated on the gauge has always been good, before and after I worked on it. At full operating temp and in gear at idle, just under half.

it has 170k on it. a little noise on cold-start and one clicky lifter should not be deal-breakers, especially if it's got good oil pressure. how long a warranty are you offering, anyway?

Maybe do what Kenny is suggesting with some bars leak and then run a really thick oil for a couple thousand miles to try and increase pressure everywhere to clean things up a bit? Like a full change to 20w50 oil with a strong additive package (I'm thinking conventional motorcycle oil or the Brad Penn stuff 911 guys like) and then back to whatever the factory recommended fill is afterward.

Kenny_McCormic wrote: *I make this guess based on how GM had those bars leaks tabs developed for the 90s aluminum block Cadillac motors that had so many porosity issues it was considered routine maintenance to stop leak em.

GM has been selling those stop leak tabs since the 70's or so... can't have Caddilacs seeping fluids in their climate controlled garages...

regarding the 5.3/4.8 swap: car-part.com puts most 5.3's within 100 miles of me about $200 more than a comparable 4.8, which is totally worth it just to keep the torque.

What's a 2000 Tahoe worth the days? Seems that since I have an engine already we should be going about this differently....

haha... maybe you're right. If the engine was quiet I think I can get in the low $5k's for it.

There's no rust. Hardly a scratch anywhere. Brand new tires & shocks. It's an LT with 3-rows and rear climate, sunroof, tow package, etc etc.. A one owner truck before I got it.

speaking of going about this differently...

I was hoping a low mileage 4.8 would be worth the $$ savings over a slightly-more-used 5.3.

if, instead, I pay an extra $600 for a 6.0 over the cost of a 4.8, does that sound like money well spent?

belteshazzar wrote: It has 706 heads on it.

Yep.

http://speedtalk.com/forum/viewtopic.php?f=1&t=28519&p=331810&hilit=porosity#p331810

I would so run the mighty 4.8! and not look back.

For the noisy lifter, run some synthetic oil or maybe diesel oil in ti for a while? If you address the coolant loss, the sludge that is likely the issue will likely fix itself, run an oversized filter too. Speaking of which, what filter are you using? Cheap ones will drain down and make any motor sound like hell at startup.

Just to downvote the 4.8 again, the one I drove, in a 4x4 chevy truck, kinda felt like driving a old TBI 4.3 in extremely good tune, except the 4.8 doesn't run out of breath at high revs. The 5.3 just feels a lot stronger.

The LSx motors are notoriously piston-slap happy when they get some miles on them. Run 'er into the ground if it still runs fine!