Replacing the lower end of a 99 Denali engine

So I finally got the word back from the mechanic. Seems like there was no oil pressure despite what the gauge read and despite there being oil in the car. The knocking was from a rod bearing that was going bad from the lack of oil and I was quoted $3200 for a new lower end (I think I got that right). What all does that encompass? A new camshaft, bearings and rods?

Is there a cheaper way to go just replacing the parts ruined by the heat?

The repair job involves pulling/replacing the crankshaft so I don’t see how it can be any cheaper to do.

A short block might actually be a better solution.

A new short block is kinda what I assumed “a new lower end” meant.

A quick google shows that your Denali has the vortec L31. Gotta be squillions of good used examples in junk yards across North America. Would bet that there’s probably 5 other types of GM corporate small blocks that drop right in place of the L31.

Might be worth it to ask your mechanic how much he’d want to swap in a low mileage used motor, even if you have to supply it yourself.

I thought he meant replace the cam, bearings and rods.

He quoted us around $5500 for a new engine. What do you mean about a new “short block”? What exactly would that replace and could I part out the good parts of the new engine? And if I pull it from a junkyard what’s to say I won’t have problems with that?

A short block is a lower end of an engine. It is the engine block itself with crankshaft, rods and pistons. It’ll also have the cam and the lifters (in most cases). A long block will have heads on it.

So I’m guessing no one rips the guts out and the garage would be replacing the short block then? How much labor is it to replace one if I get one on my own?

That would be my guess and the crankshaft is usually the only thing that’s damaged. In case of the spun insert then the connecting rod would be damaged too.

Hell, we spent $5k putting a brand new motor in the 99 Suburban a couple of years ago - I’d expect that a decent rebuilt engine for the same model Dinali could be had and installed for the $3200 your mechanic is quoting - give or take a few dollars, depending on the cost of labor. (Admittedly, we got a bit of a deal from an old friend, in exchange for working around his schedule of more urgent jobs.) But I’d compare the cost of a used or rebuilt motor before signing up for just the lower - wouldn’t want to pay that much only to discover more problems in the motor soon afterwards. (And I’m not a mechanic, but that would seem likely to me. And that statement may well be born of ignorance on my part - I freely admit it.)

But if the truck is otherwise sound, I wouldn’t hesitate to make a big repair like that, and drive it till it dies of old age. After all, it wouldn’t take many months to spend that amount on a new vehicle payment and full coverage insurance.

When I hear “lower end” I think of crankshaft and connecting rods with main and rod bearings, piston rings, and possibly pistons. I group the camshaft with the valvetrain components in the upper part of the engine. If it was a short block replacement, which includes the cam, I’d expect to hear that term, not lower end.

I lean towards replacing with a good used engine, but I gather from discussion with my colleagues around the country that in some areas it’s hard to find salvage yards that consistently offer good product. Shops in that situation will either repair what’s in there or replace with rebuilt or new.

The mountain’s name was changed from McKinley back to Denali. Maybe that means your Denali is now a McKinley.

if you spun a bearing from lack of oil then the engine is probably full of brass shavings or whatever the bearings are made from.

It’s 16+ years old. Unless you REAAAAALLY like this car or can do the work yourself then walk away. Parting it out would bring in the most money.

Even shops are suspect. I bought a long block engine years ago and they installed the heads with dry bolts. I got no compression and when I tried torquing the bolts each one of them snapped in 1/4 turn increments. I was not amused. All I asked for from them was a new head gasket and they refused. Return it for a refund or nothing. :rolleyes:

I would imagine finding a used engine for this thing shouldn’t be too difficult since it’s the same 5.7L V8 that’s in a bazillion pickup trucks. IME, major drivetrain work like this is always worth shopping around since some shops are much better set up for it than others. If you do go the used route, you should be able to get one with something like a 30 day warranty, so if anything does turn up that didn’t show up in the salvage yard’s once-over you should still be good.

So here is my quandary. I don’t want to put a ton of money into the Denali so a used motor sounds like a great deal if I can find someone to install it for me. As good as it is it is still an old car but because I’m hoping my son will use it when he goes to college I want the engine to be reliable and with a used motor, how many years can I reasonably expect to get out of it?

So I was looking online at some short blocks and it looks like I can find decent rebuilt ones with a warranty for $1200-$1500. BUT I can get a low cost full engine like this one for around $2000.

It seems to me that if I’m not going to get a $500 short block at pick-a-part that it make more sense to put in a full engine so that

  1. I’m not mating old heads to a “new” block.
  2. New block + 17 year old heads? Will the upper end be reliable? (I honestly don’t know, do upper ends wear out like lower ends?)
  3. The install is actually easier since it is dropping in a whole motor. I might save an hour or two in labor costs.

So tell me where I am wrong in the 3 assumptions.

You could slap the old heads on a new block but I wouldn’t advise it. Not without refacing the mating surfaces and valve jobs. New block means new rings so the compression will be at the maximum.

If you go the short block route, your mechanic should send the heads to be inspected and resurfaced at a machine shop before installing them on the new block, or he might have the tools and expertise to do it himself. If the heads check out okay, there shouldn’t be any problem putting them on the new block.

The thing with used engines (and I suppose it also applies to used heads on a new short block) is that under normal circumstances an engine should outlive the car. It’s not like in the old days where you could reasonably expect to get some finite number of miles out of an engine, and so starting from 0 miles with a new engine would get you considerably more usage than a used one that’s already got some miles on the clock. The drawback of a used engine is you’re taking a bit of a gamble since you don’t know its history, but the inspection a reputable salvage yard will do along with careful monitoring during the brief warranty period should catch anything egregious.

That said, if the car is in otherwise good shape (did you fix the PCM problem?) I could see how a crate motor would be appealing. You’re definitely right on point #3, especially if the mechanic has to farm out the head work to a machine shop. That’s something where hopefully you can get him to run the numbers to see how much more the long block would actually cost you than an installed short block.

Although that brings up another big advantage of a used engine. A long block usually comes with the bare minimum of stuff they can bolt to it and reasonably call it an engine. So you get a bunch of extra labor swapping over the spark plugs, water pump, intake manifold, etc. It depends on the junkyard, but used engines usually come pretty close to ready to drop in, minus only the fuel and ignition system stuff, the alternator, starter, and AC compressor. (Although once I bought a used engine that amazingly came with everything, including the air cleaner and a clutch!)

A used motor is by definition no longer a predictable piece of machinery. Anyone giving you a number is simply guessing.

  1. Mating old heads to a new block isn’t inherently a problem. New value seals, springs and a general cleaning and inspection would be advised though.

  2. Heads do indeed wear out, but the parts are pretty cheap and easier to replace than the lower end. Swapping a munched rocker arm is a lot simpler than replacing a crank bearing. The head castings themselves are fine for a lifetime or two without anything major.

  3. Totally agreed that the install is easier for a complete long block than it is for a short block. With the short block you have the added steps of disassembling the valvetrain and the heads from the block.
    You’re right, it’s a labour $$ versus parts $$ scenario.

So it is looking like three options.

Absolute lowest cost tear a short block out of a used POS (might even find someone parting out a 1/2 ton using the same engine) and pay someone to tear my engine apart, install the block and reattach everything. Maybe (probably?) have a machine shop check out everything before putting it back together.
Pro: Super cheap. Hey it’s a car to get me from here to there and back daily.
Con: Who knows how it was driven before. Could be spending money to get the same problem now or a month from now or six years from now - who knows?

Crate engine. All the machining is done. Theoretically an easier install. If this were a newer or better car it would be a no brainer.
Pro: Most reliable of the options. Might be better having a full engine rather than just the low end if I want to privately resell it later.
Con: A lot of money for a decent (not great) Denali.

New low end while keeping the rest. If I go the route my mechanic is pricing, the way to go since new full engine is $2300 more (but I need to make sure it is a full short block and will be machined)
Pro: Middle ground probably the best fix to solve the current problem.
Con: But not the best general solution. Less money to solve the problem short term; more money to solve the problem long term.

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