Hello all,

A couple of months ago I had a catastrophic engine failure while tracking my car (1999 M/T hatchback) at Putnam Park. Engine failed coming out of Turn 2. Loads of coolant in the crankcase but no hole in the block. I was hoping it was maybe just a headgasket, but no such luck.

Started taking it apart a couple weeks ago, and found coolant just everywhere. In the intake manifold, in the intake ports, all over. Got the heads off and piston for cylinder number 6 is no longer connected to the crankshaft. I still don't see major engine damage but the piston made light contact with the valves and I can push it down in the cylinder with my hand. Some damage to the piston face. The liner is cracked in multiple places on that cylinder, which I have gathered from doing some research means the engine is dead and not rebuildable. There is also significant aluminum shrapnel in the number 5 and 6 lifter trays, which I think is probably bits of broken block carried up from below.

I'm not running an oil cooler or a baffled pan on the car. I have Z51 springs, Bilsteins and Progress bars on stock size 200 treadwear tires. I hoped it wouldn't have enough grip to oil starve but I think that plus high oil temps (it runs 265-280F on the track) likely resulted in a rod failure. I'll tear it down more once I get the engine out of the car but I think I know enough now to say the motor's junk.

So question now is what to do next. I've been reading up and find that the LS1 is basically a one-time use engine and can't be overbored, and I'm not finding any of them rebuilt. I can't really even find a suitable block to use for a basis of a rebuild and anyway I will need at least one new piston and rod and who knows the crank condition.

I'm looking for something cost effective to get the car back together. I use it as an occasional weekend cruiser with my wife, my daughter drives it for her fun car, and I take it to the track a few times per year. Ive owned the car for three years and it gets driven about 1000-1500 miles a year. It has 51k miles on it and I paid $16,500 for it. So I'm looking to get a fun occasional use car back on the road but I'm not looking to dump a ton of money into it. I am not really looking to make a lot more power. Not because I don't like power, but more power is more stress on the gearbox and clutch, more heat to reject, more speed that has to be scrubbed off with the brakes. I have made the mistake of going down the "more power" on a track day car before and regretted it. It becomes a never-ending series of fixes and upgrades and the car becomes a money and time pit and become worse and worse to drive on the street. I really hoped to avoid that with this car by just doing very minor suspension upgrades. I enjoyed the way it drove on track. It was 'fast enough' to be entertaining and gave me a good platform to use to work on my driving. I would like to keep the car streetable and I want to keep A/C, power stuff, etc.

So, now I need to decide what to do for a new engine. The obvious answer is "LS3 crate engine", but those start at $9700 and then you add the cost of the 24x conversion box, new throttle body, extension harnesses, etc and it's pretty quickly $10,500 or more for a 430hp engine. I have read a few swap threads and while it seems pretty straightforward, there are a few things about the fit-up I don't love.

I have considered buying a used LS1 and rebuilding it, but I would want to do an overbore and start with a new cylinder, and it seems risky to expect to be able to even get a hone out of one. I guess that's why nobody offers a remanufactured engine. I have never rebuilt an LS engine, but I have rebuilt other engines, and I enjoy the work. But it does take a lot of time and from what I've seen, a good condition salvage take-out LS1 or LS6 is $4000, and I think by the time I rebuild it I'm going to be in it for another $3-4k in parts and machining, so not really coming out ahead versus the LS3 to have less power and do more work.

I'm very intrigued by a 5.3L remanufactured engine that ATK offers. $5087 with $275 flat rate shipping, no core charge and a two year warranty. This looks like a factory rebuild but with the cylinder deactivation removed and a comp 223/231 cam added. It's got 243 heads and they claim it makes 475 hp/430 ft-lbs with a vic jr and a 4-barrel. I figure with long tube headers and exhaust with a LS6 intake manifold and accessories and such hooked up it should be a 100hp or so upgrade over the LS1. I wasn't really looking for more power but I won't say no to it.

Does anyone have any thoughts on going this route? It seems to me to be a pretty easy and cost effective way to get to good horsepower. I think it should be an easier install as well because it has a 24x crank. They say only the cam position sensor harness needs to be extended.

Will I need to upgrade injectors? If so, what should I use for an upgrade, and can I plug those in directly and use my LS1 fuel rail with an LS6 manifold?

Does anyone see any red flags with this route, or any gotchas that will make this more complex than i'm thinking it will be? Any opinions or predictions on the streetability of that cam? It feels weird to go to a smaller displacement engine but the power (especially the hp/$) is sufficient. I like the lower torque and 9.9:1 CR better than the LS3 anyway for track use, because I think it will have a wider margin to detonation and it will put less strain on the transmission.

Thanks in advance for any thoughts and feedback and sorry for such a long post but I wanted to get relevant info out there early.

 

Couple photos


Cracked liner on #6

This piston no longer pistons

Cylinders full of coolant

Aluminum debris in lifter trays

 

A 5.3 L33 would be a complete bolt in if you could find one. Cam and spring change they run very well. It’s like a mini LS6.

The 5.3 you mentioned might likely be cammed for a carb which wouldn’t play well with EFI. You would have to ask them. You would also want a 24X reluctor installed if not already there.

 

5.3's are a solid engine base to build on. Im actually somewhat surprised GM never offered it as an optional engine on C5s. It's basically a modernized version of the Chevy 327 V8..

 

That ATK offering looks pretty good. Good HP and TQ out of a small displacement engine AND it's still aluminum. I noticed it's a long block so I'm thinking you could use a lot of your current external items that were not affected by the catastrophic failure. I'm curious as to the details of the lead up to the destruction. How many miles on engine? What oil were you running? What gear and approx RPM through that turn? In my LS3 C5Z I see 280F often (no cooler) but I change oil every 4th track day. Good Blackstone reports. I have an Accusump for added protection but I try to keep the RPMS down (4th gear) in long sweepers.

 

That’s my thought as well. I think I will use an LS6 intake manifold and probably go with long tube headers to take advantage of the cam and it will save me work of changing those components out later. I would probably reuse a lot of other parts from the factory motor (replacing some of the hard to access sensors and such now)


running about 5000-5400 RPM in third gear around the time of the failure. It was right at the start of a second push lap and it was about a 75 degree day. Water temps were not high, but oil temp was in 280 range. I use Mobil 1 10W-30.

the car has 51k miles on it. I’ve done maybe 6 track days on it. This was my third track day this year / on this oil change. I bought the car Sept 2023 so haven’t had it long. I am the second owner and it seems to be a typical original owner corvette. No signs of abuse, very little mechanical wear, etc. I’m at a loss to explain the failure other than to surmise the oil starved a bit and was too hot. I knew I was taking risks tracking the car without a baffled pan and cooler but it was a mild day and I had gotten away with it previously in hotter weather.

Live and learn. I will upgrade the pan with baffles and install an oil cooler when it goes back in. It has been recommended to me to upgrade the oil pump to a melling 295 when I put the new engine in. Any thoughts on that?

 

Man that's kind of a sad story. Found a super low mile original owner C5, and blew it up in 2 years....oops

 

ATK makes me nervous - I know of a few of people who have had issues with their Gen 1 builds over the years. There's very little profit in engine building, if you see something that is significantly cheaper than competitors, there's a reason.
If you're able to legally do the Gen IV conversion (which is moving around some sensors and a custom tune) Thompson has a 5.3->5.7 shortblock in stock that would be perfect for you
https://thompsonmotorsports.net/prod...46ci-800hp-24x

For the record, the LS3 crate motors are out of production - there are a few left on the shelves, but from what I hear the QC on the final run was not very good.

 

RobIndy, the PO of my '99 FRC nuked the mostly stock LS1 engine at Putnam back in July 2015. The 5w-30 oil temps hit 300F degree and the lack of rear steam cross over tube with the LS6 intake manifold lead to knocking the ring lands off #7 piston. He ordered a Thompson Motorsports Stage 2 aluminum 5.7L short block (based on the factory L33 5.3L block) and had it shipped to Mike Norris Motorsport in Indianapolis. Mike swap engines and added a set of LS2 take off 243 heads and a bunch of Comp Cams valve train goodies. Folks have swapped in stock L33 long blocks into their C5 in the past, but you may not like the torque drop.

My ownership has centered on upgrading almost all the systems / components for dealing with track duty. You may also want to read through the Spec Corvette rules, they have some solid recommendations mixed in there for making any C5 more reliable road course track worthy for say even HPDE events, not just solely for hard core track only on race cars. Best of luck on the rebuild!

 

You guys are kind of talking me into sourcing a serviceable L33 or LM4 block and building my own 5.3. There’s a ratty L33 for sale on eBay for $900……

I’ll have to see how the crank looks when I get the engine out of the car and apart. Then I can assess how many parts I can salvage from the blown motor.

I thought I could have a decent HPDE car without a lot of upgrades by keeping the power at stock levels and just working on suspension and driving. Should have just bought one of these old ASA cars….. oh well, my daughter likes the Corvette.

 

For autocross yes, for HPDE no. The owner's manual recommends adding 1Qt of additional oil for performance driving, I assume you were doing this.

 

I'd double check that, I just called my local GM Performance Parts dealer, and he told me that the LS3 430HP, 495HP and 525HP are still in production and he has not heard of any plans for obsolescence at this point. And they are still appearing in the 2026 Parts catalog: 2026_ChevyPerformance_Digital_Catalog_V1

 

It might be in the catalog, but type the part number into any GM parts vendor, it doesn't come up. SD Parts is the largest GM parts dealer in the US https://sdparts.com/search.html?q=19...ation=vertical if they can't get it, no one can
The blocks went out of production - which sucks because the LS3 blocks were the basis of a lot of the aftermarket crate motors.

 

Is that an older Part number? sdparts.com/search.html?q=12673475&orientation=verti cal

 

I did not add an additional quart of oil when I went to the track. Perhaps I should have. To be honest I have never looked at the owners manual…..

 

Every chance I get I pickup a used 100-130k L33 05-07 from Ebay when I see for less than the cost of a set of tires

I use for 600 to 800rwhp daily driver swaps , they will go 300k miles stock bottom end untouched up to 1000bhp if you know what you are doing

here is the latest one




What you want is to be able to wipe the carbon coat off the piston in < 30 seconds using a dry paper towel

That tells you the PCV system and maintenance was most likely left OEM no funny business, no stuck hard carbon diamond-like deposits in the ring lands

All the lifters should look spotless rollers spin the same feel the same look identical


golden colour without any burning smell or burnt hard black carbon is ideal, it doesn't get better than this for 100k miles


gen4 rods are floating pin, forged steel


You should scope it out and get it from a crashed truck,


That way you know it was operational when it was pulled and likely still runs like a typical truck engine

 

LOL!! You're not alone!

 

Pretty shitty thing to say to a guy you've never met who is using his Corvette for.... Corvette things

The engine doesn't "make" the car, and he's fixing it. Not like his oMg So RaRe '99 is going to the junkyard to rot. Jeez

To the OP- I bought my '02Z with a blown motor. Sad story, it blew up doing Corvette things too

Anyway, I built an AMS Racing 408 for her. Just tossing it out there that other options exist, depending on budget. My 408 is probably in the $15-18k range, which is orders of magnitude more than a cammed 5.3. Has not been on the dyno yet, but I estimate mid 500's whp

All things considered, I would do my 408 again, even if I could make more power 5.3+turbo and save $6-8k. I'm also an idiot lol

 

What is a "corvette thing," can you please describe?

 

Shitty? No personal attack, name calling, etc. How would the comment be better or worse if I met the OP....even once? Just seemed like a sad tale surviving it's first 24 years with super low miles only to meet an untimely demise.

Sorry that triggered you.....Christ, this is getting to be a sensitive group.