Hello,

How many miles until a new engine needs a rebuild?

Thanks for help.

 

It depends on a lot of different variables, so without knowing the specifics of the engine, there not really an answer. Some engines don’t need to be rebuilt for hundreds of thousands of miles, some engines have a rebuild interval measured in hours.

 

OK. When I do an engine compression test what lowest dry psi and what lowest wet psi that will tell that the engine is healthy and doesn't need a rebuild?

 

I would prefer to do leakdown test over a compression test. Compression test results can actually vary depending on how fast the engine is turned over during the cycles. A leakdown is more consistent. For an old engine, up to about 20% is considered ok, but more than 20% and you do need to consider a rebuild. However, a relatively new engine should be 5-10%. Any of the cylinders that are significanly lower than the others might be a cause for concern as well.

 

OK, Thank you for the info.

 

How long do shoes last

 

Anywhere from a few to quite a lot. I think you are too smart to ask such a stupid question. That's like asking how many years do people live??

 

Exactly. It's all about comparing the engines current state to it's healthy state. Intended usage, etc.

You can't gauge it by compression numbers alone because engine have different compression ratios that will reflect a different number on the compression test. Which as said can be affected by cranking speed etc. Static compression that is affected by the valve events which results in dynamic compression which is what you see on the gauge.

There is no single answer. The leak down test is about the most solid test you can do. But that also doesn't tell you the condition of things like bearings, lifters, springs etc. You just have to use common sense here. Does it run good? Does it knock or make noises? Etc.

Race engines are torn down between races, street engines go till they die, which in some cases is 400 thousand miles or so. So you can see how there is no single answer to your question.

 

If you do a compression test on a warm motor and you see wide variances between cylinders you have problems, or if you squirt oil in cylinders and pressures go up a lot, you have problems.

 

I don't think it is a completely off-base question. Todays engines will last longer than yesterdays, mostly pending on how they are taken care of. A short answer when I have reviewed seemed to be up to an average of about 365,000 miles for standard 100% stock LS based architecture. This is given proper oil changes, warm up time, external cleaning, plug changes, etc.

 

The way he put the question is like asking "How high is up?"

 

You're right, his question can be answered with 100 if's. But that doesn't seem like much of an answer

And essentially your answer is "depends on a LOT of things". Which is the point we are making. There is no actual answer because

_ A. 50 miles
_ B. 30,000 miles
_ C. 200,000 miles
X D. Not enough information to answer the question

 

I'm starting to feel like an ******* to someone that may not have english as a first language. That's not my intent.

Abdullah. You'll have to give us a lot more information about the engine and how you plan to use it.

Or, maybe tell us what problem are you having that we can maybe help you figure out?

 

The correct answer is 32.

 

It depends on how the engine is built, how it's used, and how well you maintain it. For a factory LS engine that's properly maintained, there's no reason it shouldn't last 300k miles. Many go 500k+ miles before needing rebuilt.

I have friend's engine that I rebuild every other winter, just 2 seasons of racing on it. It's a highly competitive factory stock engine. A 355ci SBC that pushes the envelope of every rule limitation. We have 4 different custom hydraulic flat tappet camshafts for it spec'd for whichever of the 4 common tracks he's racing at that weekend. They're all .480" lift with the smallest being 242/246 @ .050" and biggest being 248/258 @ .050". It has stock smog heads, flat top pistons as light and tight as we can get them within the rules (quench is just .026"), just .0014"-.0016" rod and main bearing clearances, runs on 0w-20 oil, a 500 cfm 2 bbl, and spins to around 6800 rpm. It makes all of 360-365 crank hp. It has less than 1,000 miles on it when I rebuild it, and it's showing it's age at that point.

Like I said, it just all depends on that particular engine and it's use.

 

 

Hi Abdullah,

I think that's a very interesting question regarding stock LS engines, basic bolts on, normal use and good maintenance.
I'm happy you asked this on LS1TECH, it's an excellent topic in my opinion.

GM benchmarked the original LS1 during development during in the mid 1990's to go 200,000 miles and all critical parts and tolerances be within the limits for a new parts/ new engine. This was the first time that had ever been done by a OEM manufacturer. The LS1 passed the 200,000 mile bench mark tests. The oil used was Mobile 1 5w-30 Synthetic.

I had a long PM exchange with a former GM engineer that was heavily involved with the development & testing process

After 200,000 miles statistically speaking if all of the "average well cared for LS1 engines parts" are within the critical tolerances for new parts - it's hard to really know how long to expect these engines to last. I know a dozen people with 200,000 + mile LS engines, several with 300,000 + mile ones. A friend torn one down that had factory cross-hatch in the cylinder bores with 297,000 miles.

Another engineer said the bench mark test was 25,000 hours of operation. If a car or truck averaged 40 mph for that time period that would imply 1,000,000 is very possible in some cases - in theory.

I think we will see a some 500,000 + miles LS engines and a few spectacular ones that roll the 1,000,000 mile mark.

I know someone that paid ~$9,000 for a 2010 GM truck with 228,000 miles on it...that would have been hard to imagine 20 years ago

Modified engines are a wild card. My heads & cam LS1 ran fine when it was pulled for a new 416 stroker. The old LS1 had 164,000 miles and 132,000 of that was with a heads & cam package. I feel very confident this modified LS1 would have went at least 200,000 miles. Of course ~50,000 mile valve springs changes and retainers, locks and valve seals etc were normal maintenance for this engine.

In my opinion what kills a lot of engines is failure to flush coolant regularly and replace it. That eventually leads to overheating and engine death.

FWIW - My 91 RS Camaro had 389,500 miles on the original small block Chevy 305 V8 and it still ran great when the car was LS swapped.

Older Cars & trucks with carbureted engines have shorter lives often less than 100,000 miles. Cold start is usually to rich and the excess gas washes the oil off the cylinder walls on start up. That causes accelerated wear and dilutes the oil.

Best Regards,
Wade

 

GM (and basically all the other automakers) has learned that lots of shorter-duration testing is much more meaningful than fewer longer-duration tests. Thus, GM doesn't actually put 25,000 hours on any one test engine. They don't actually put 300k miles on any one test engine. They have lots and lots of test engines that cumulatively log tens of thousands of hours and many hundreds of thousands of miles.

They have developed statistical models that correlate long term durability with (much) shorter tests. For example, they test multiple examples on an engine dyno durability test cycle that runs for 250 hours, stopping only for inspections and oil changes. The engine is run exclusively at WOT, and engine speed varies every 30 minutes between peak power and peak torque.

They also contract 3rd party firms to run a fleet of test cars. The test cars are driven about 18 hours a day by varying drivers. Usually each test car will accumulate 30k-50k miles. Any abnormalities or issues are studied, and the cars torn down and inspected once the test running is complete.

There is more; these are just two examples of how GM evaluates their powertrain durability. Where the rubber REALLY meets the road, is in hindsight - when you can look at real world production examples that have been in real world customer hands for years and years. The LSx platform has proven to provide EXCEPTIONAL durability and reliability in that regard.

Still, the machines, tooling and people that build engines are all susceptible to problems, and there is definitely such thing as a "monday morning" engine. While each individual part may be within tolerance, you end up with an overall assembly that doesn't work as well as another that was built with parts all closer to nominal specification. We call these WoW or BoB engines. Worst of Worst and Best of Best.

Hope that helps give some insight.