Car guys - should I do a top-half rebuild on my GM 5.3L?

tRidiot · May 19, 2019

So I have a small leak in the heads, I lose coolant and it is making its way into my oil, slowly but surely, getting worse over time. It's not terrible, but I've known for a while.

I've got the Castech 706 heads on mine, lots of you probably know what this means... poor casting meant cracks that led to slow leak of coolant. I've replaced the water pump, replaced the radiator, it's not leaking externally.

So anyways... the question is - top-half rebuild, or full replacement? One friend of mine has told me in the strongest possible terms I should do the whole rebuild or replacement and NOT to do a top-half only, as it will surely have something major let go in the bottom half after 3-6 months.

The problem is, my mechanic tells me a top-half will run me about $2k with him - for a replacement, I am seeing online prices starting at $2k and going way up from there. For the motor alone.

So, car guys, what do you think?

Oh, and I will likely need the transmission sometime in the next year or two, too... <sigh>. I'm at 265k miles right now.

doctorjj · May 19, 2019

I’d go with new motor if you plan on keeping it.

RKM · May 19, 2019

Back in the day when I street raced I always tried to to a complete build on whatever....engine, clutch, tranny..etc. Sometimes I didn't have the cash to do it, but when I did I tried to replace everything. Just my 2 cents.....

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BReeves · May 19, 2019

Do it right or get rid of the truck, simple as that.

jfssms · May 19, 2019

Doc, you didn't mention the year model. I suggest you look at a new Chevrolet performance motor from someone like Scoggins Dickey.

NightShade · May 19, 2019

If I was doing it I would find a junk yard motor and rebuild that. If you can drive the one you have for now you can take your time doing the rebuild. If you are planning to keep it I would absolutely go this route so that you can do everything right and then only have it down for a day or so when the swap is done. A salvage yard motor for rebuild can be had in the 500 range not far away. http://car-part.com/cgi-bin/search.cgi?userSearch=int&userPID=1000&userLocation=All+States&userIMS=&userInterchange=>B>B@O&userSide=&userDate=2007&userDate2=2007&dbModel=15.27.1.1&userModel=Chevy Tahoe&dbPart=300.1&userPart=Engine&sessionID=11000000090961618&userPreference=price&userZip=73044&userLat=35.8319000&userLong=-97.4802000&userIntSelect=2256977&userUID=0&userBroker=&iKey=&userPage=21

But sit down and figure out what you want to do with it. If you want something that will last having a proper rebuild with a couple upgrades can make that happen. If you want to do some mods later on a proper rebuild with some choice upgrades are required. If you want something so you can sell it and get something else drop about 1750 on a salvage motor with around 91K miles on it and have a swap done then sell the old one for 500 bucks and be done with it, this is also an option if you just need to have something going for a couple more years till you can trade it off.

And if you decide to go the salvage yard route let me know and I can do the pick up and all for you. Will only cost you my fuel which will probably be cheaper than their shipping.

Glock 40 · May 19, 2019

So you have a early-mid 2000s Tahoe or Suburban? No way I would drop 2k on a top end rebuild. Have you looked at possibly doing a GM crate motor replacement? The performance ones are pricey but a plain jane replacement may not be to bad. If you really want to drive this thing for a lot longer that would be the option I would check out. I had multiple Tahoes in that generation and my last one had the mystery coolant leak. Never could find the leak sent a oil sample to Blackstone Labs and it has traces of coolant. I used a gallon a year for a few years till it finally started leaking bad. I ended up trading it off when it was puffing smoke when I would start it.

918evo · May 19, 2019

Get a salvage engine and save the money and possible headache. A salvage yard 5.3(99-06) runs $500-800. Find one with low miles and be done with it. You should be able to buy the used engine and labor for under $1500.

NightShade · May 19, 2019

I want to say his is newer than 06 that means about 1700 to 1800 for a motor with about 91K on it. A weekend with a cherrypicker and a case of beer for a couple of friends covers the labor though. Or in my case a pizza and a place to crash.

And I should also say that even if it is older as long as things will work swapping in the newer model may end up having a longer lasting motor anyway. You can always put a newer engine in an older vehicle and be legal, the other way can cause issues with the man if you get caught.

Shadowrider · May 19, 2019

I agree with blake711. If you are going to be keeping it, drop a crate engine in it. You can deal with the tranny easy enough when the time comes.

Car guys - should I do a top-half rebuild on my GM 5.3L?

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