Replacement 5.3L engine

[BretD04GMC]

The 5.3L LM7 in my 2004 Sierra has just suffered a cracked cylinder head, and coolant is getting into the oil. Blackstone Labs oil analysis also shows bearing and crank wear.

At this point, my feeling is that the motor is done, so I'm looking into replacing it with a new crate long block. The question I have is are there any differences between the LM7 based on what year truck it went into?

Summit Racing has an LM7 long block for $3,000, with $300 core charge. They have it labeled as a "1999" truck engine:
http://www.summitracing.com/parts/nal-12457705/overview/

Searching online also pulls up a GM 5.3L crate engine with part number 19301546 – this engine shows up as the 2001-2004 truck version. However, the cost jumps to $3,380 with a $2,500 core charge on most sites:
http://www.gmpowertrainwarehouse.com/19301546.asp

 

A third option is this from Turn Key Engine Supply. Chatting with Kolby at Turn Key, he says this long block is a stock LM7, and that the 350HP/350TQ is acheived on the engine dyno through headers, more aggressive tune and no emissions. GM rates them at 290-300 in the vehicles due to emissions, exhaust and engine driven accessories:
http://www.turnkeyenginesupply.com/turn-key-engine-885301lb-ls327-5-3l-350-hp-turn-key-long-block-assembly/

 

My understanding is that the LM7 was pretty much the same for the entire 1999-2006 run. The only HP differences were achieved by GM tweaking the programming in the ECM and maybe some exhaust updates.

 

Does anyone know for sure if this is true?

The Summit engine is a good price, but I don't want to risk some sort of fitment issue.

 

 

Thanks!

[BretD04GMC]

Doing some more digging, it appears the Summit engine is the only NEW crate long block. The part numbers I'm coming across are remanufactured engines, and that's why they're broken out by year, and also the reason for the higher core charge:
http://www.crateenginedepot.com/All-50-53-57-Liter-V8-Goodwrench-Engines-C718.aspx

[Nanotech Environmental]

Sux that the head cracked like that, as these are generally quite bulletproof engines........

 

Would it be of value to you to find a good one out of a wreck? Apparently they can be had for cheap.

[BretD04GMC]

Sux that the head cracked like that, as these are generally quite bulletproof engines........

 

Would it be of value to you to find a good one out of a wreck? Apparently they can be had for cheap.

Used engine out of a wreck isn't an option. Too risky.

 

Still trying to pin down exact details on the various 5.3's out there. The Summit 5.3L may only be rated at 270HP, since it's flagged as a 1999 engine. The reman. engines are clearly broken down by year, so there does appear to be differences and not all LM7 5.3's are the same when it comes to stock replacement.

 

I'm exploring going with Jasper Engines, through a friend's shop.

[Chris]

Cam profile changed around 01 somewhere i believe. That helped give it the bunp in power.

[RyanbabZ71]

Cam profile changed around 01 somewhere i believe. That helped give it the bunp in power.

99 was 270 Hp

 

2000 was 285 HP

 

 

 

 

Ryan

[Chris]

99 was 270 Hp

 

2000 was 285 HP

 

 

 

 

Ryan

It went up a second time though because the 4.8 went up to around 285.

[BretD04GMC]

99 was 270 Hp

 

2000 was 285 HP

 

 

 

 

Ryan

By 2004 it was up to 295HP, and I believe I read it peaked at 310HP in early 2007. At that point the L59 version took over.

[00Silverado4x4]

By 2004 it was up to 295HP, and I believe I read it peaked at 310HP in early 2007. At that point the L59 version took over.

The L59 was just a e85 capable version of the LM7 which was also rated at 295hp, both had cast iron blocks. The 310 HP was the L33 (aluminum block)

[BretD04GMC]

Replacement options are looking to be a bit of a hassle. The new GM crate is flagged as a 1999 engine, meaning it likely has 270HP. So far, no one I've connected with can do more than guess.

 

Year specific reman. engines require $2,500 core charge. Not too appealing.

Some engine shops list a replacement LM7 5.3L, but when asked about the HP and TQ numbers they respond with "it SHOULD be 295HP". In other words, they don't know for sure since there's so many LM7 variations out there.

One shop even lists having a 350HP LM7 option, but when questioned replied with "That's a stock LM7. The 350HP is acheived on the engine dyno using headers, no emissions, and an agressive tune. GM rated those engines between 290-300HP due to emissions, exhaust, and engine driven accessories."

So why even list it, when they also list an OE replacement LM7 with quoted HP as 295? Again though, no guarantee that it's actually a 295HP LM7. Everyone just seems to use that number since that's what the later LM7 and L59 put out.

[00Silverado4x4]

Worst case you get the crate engine and then use someone like Black Bear to tune it.

[BretD04GMC]

Worst case you get the crate engine and then use someone like Black Bear to tune it.

Tuning on my truck could be tricky since it's also a hybrid. There's some extra stuff the ECM does and in the 10 years I've owned it, I've never come across any handheld tuner or tuning shop that can modify it.

 

I even had a friend who was working with HP Tuners, and when I supplied them my VIN they said couldn't touch it.

[BlackZ71Silverado]

Your best bet power wise is to find the 2005 LM7 engine. That was the last year the engine was refreshed with the better, updated pistons and rods. I am pretty sure that was the an electric fan year as well, not sure when that was changed.

It's been a few years since the LM7 has been used so there should be some out there.

 

 

EDIT : You say Blackstone told you there is bearing & crank wear. How did they come to that conclusion?

If you had a head crack, replacing the heads should cost less than a new engine. You also don't have the hassle that goes along with a complete engine swap.

 

 

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[white1500]

I would go with a used engine with relatively low miles (<100k), test compression, complete preventative maintenance (open it up) and possibly upgrade parts/tune if you can budget for it.

 

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[BretD04GMC]

Your best bet power wise is to find the 2005 LM7 engine. That was the last year the engine was refreshed with the better, updated pistons and rods. I am pretty sure that was the an electric fan year as well, not sure when that was changed.

It's been a few years since the LM7 has been used so there should be some out there.

 

 

EDIT : You say Blackstone told you there is bearing & crank wear. How did they come to that conclusion?

If you had a head crack, replacing the heads should cost less than a new engine. You also don't have the hassle that goes along with a complete engine swap.

 

 

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using Tapatalk

Blackstone found high traces of lead, which according to them indicates significant bearing wear and is a common find when coolant gets into the oil. They also found high iron levels, which they tell me indicates crank wear.

 

Due to the hassle of finding a suitable replacement engine, replacing just the heads is another option.

 

I really wanted to drop in the LS327 crate engine that GM offered, but it's been discontinued and is no longer available.