When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Pulled heads on my ls1 with 250k mi. Pass head was clean as well as the plugs and drivers side head was covered in carbon and so we’re the plugs after about 300mi, car smokes extremely bad at wot and burns 1qt every 150mi but the power still feels there. Compression on that side was 160-178 leakdown showed valves were leaking and no major signs with rings. With the heads off passenger side cylinder walls still have clear crosshatchings and look perfect and all drivers side are scored, lightly but still scored. Gas mileage has recently dropped from 15 to 10 mpg after a stall with stock heads and cam which seems excessive. I’m wondering if the cylinders could possibly be washed from injectors, but more importantly what would cause one side to be scored but the other side be perfect?? Scores are light and can’t be felt with a fingernail.
Not clear on the 'after 300 miles' comment. Are you saying the plugs are carboned up in 300 miles? Anyway, I think youve answered you're own question. In a 1/4 million miles, everything is going to wear!! Including the injectors. Since the drivers side has way more carbon, and your fuel mileage dropped considerably, I'd say the drivers side injectors are having issues supplying the correct amount of fuel. I agree you may be washing the cylinders, and it probably has been doing so for many miles. It's finally reached a point where it's noticeable in your fuel mileage. As for the scoring......RUN IT!! That motor has the right to show a bit of wear in 250,000 miles!!!
Not clear on the 'after 300 miles' comment. Are you saying the plugs are carboned up in 300 miles? Anyway, I think youve answered you're own question. In a 1/4 million miles, everything is going to wear!! Including the injectors. Since the drivers side has way more carbon, and your fuel mileage dropped considerably, I'd say the drivers side injectors are having issues supplying the correct amount of fuel. I agree you may be washing the cylinders, and it probably has been doing so for many miles. It's finally reached a point where it's noticeable in your fuel mileage. As for the scoring......RUN IT!! That motor has the right to show a bit of wear in 250,000 miles!!!
yes the plugs looked like that after 300 miles. I was thinking of getting the injectors flow tested to see if there’s something wrong with them. My main concern is the oil consumption. If it’s a mixture of the heads and injectors that are causing it to burn oil and drink gas then I might as-well just slap new heads and injectors on, however I don’t want to go through that just for it to be the same as before. You think the rings and scoring would be causing that much smoke?
Dint forget that the O2 sensor may be old, or bad, on the bank rhat has the scoring and excessive carbon. This may not be a mechanical problem but more so a bad O2 causing an overly rich fueling situation on that bank.
Dint forget that the O2 sensor may be old, or bad, on the bank rhat has the scoring and excessive carbon. This may not be a mechanical problem but more so a bad O2 causing an overly rich fueling situation on that bank.
that’s a possibility but then I still have the oil consumption issue which fueling wouldn’t necessarily explain.
So you bought a piece of **** Friday afternoon or Monday morning built LS1 that only lasted 250,000 miles. Yep, sometimes it happens. Such is the nature of mass production. The LS1 was designed for a 300,000 mile service life, and many far exceed that, but you got a bad one. Average means some are below average.
that’s a possibility but then I still have the oil consumption issue which fueling wouldn’t necessarily explain.
It would explain the oil usage because given a long enough period of time of the cylinder walls being washed down by excessive fuel would prematurely wear down the piston rings on that bank.... It's all tied back (IMO) to excessive fueling on that one bank. Someone mentioned this car having 250K miles... Is it still running on the original O2 sensors?
Your cylinder walls are in poor shape. It looks like the rings etched into the top of the cylinder. As I mentioned in your other thread, Run a 320 Ball hone through the cylinder to clean them up.
Does that etching occur as the rod is "rolling over" to the point where it is about to then start pulling the piston back down into the bore? It seems the rod "rolling over" (for lack of better wording) could induce a little wobble into the piston head and cause the etching. I'm just curious about this as I've never seen that type of ring damage at the top of a cylinder before. I've seen the ring it leaves at the top of the cylinder where the rings don't get up to... But never etched in witness marks from the rings themselves. Very neat that you caught that in the pictures. You have a sharp eye.
Correct me if I'm wrong, but is that oil in the cylinder? I see what looks like a golden liquid that is streaking down the cylinder walls. If that is the case, the rings have left the building and that clearly is his oil consumption problem, and lack of power, and carboned up components.
Last edited by Kawabuggy; Jun 3, 2022 at 03:17 PM.
I've owned a few real clunkers with high mileage over the years that had not been well maintained.
Before I invested a dime in heads / injectors, etc, I would run Sea Foam (high mileage) through it, several times, changing oil after each cycle. I've managed to free up the oil control rings on a few this way.
As others have mentioned, nothing wears cylinders like overfueling (maybe under-oiling, sugar-in-the-gas-tank..but you get the idea).
yes the plugs looked like that after 300 miles. I was thinking of getting the injectors flow tested to see if there’s something wrong with them. My main concern is the oil consumption. If it’s a mixture of the heads and injectors that are causing it to burn oil and drink gas then I might as-well just slap new heads and injectors on, however I don’t want to go through that just for it to be the same as before. You think the rings and scoring would be causing that much smoke?
As for the scoring, no. That's a lot of smoke. I think your rings are junk...... I'll also add, regardless of LS1, or LS ANYTHING going 300,000, 400,000, 500,000+ miles, there's absolutely no way that those engines are producing the same power level they did at 25,000-75,000 miles. Period. IMHO, at 250,000 miles, ANY engine could use a rebuild.....
Last edited by grinder11; Jun 3, 2022 at 09:21 AM.
As for the scoring, no. That's a lot of smoke. I think your rings are junk...... I'll also add, regardless of LS1, or LS ANYTHING going 300,000, 400,000, 500,000+ miles, there's absolutely no way that those engines are producing the same power level they did at 25,000-75,000 miles. Period. IMHO, at 250,000 miles, ANY engine could use a rebuild.....
Your assertion that high mileage means reduced power is incorrect. I have personally witnessed LS based motors make within 5HP of the same reading with over 100k miles between dyno pulls. I have seen multiple 200k mile plus engines that still show visible crosshatch in the bores, which used to be a sign that the rings were not even fully seated yet. Modern machining tolerances combined with modern oils have drastically changed the wear expectations on these engines compared to old school stuff that I grew up with. You also have to take into account that overdrive transmissions allow for much higher mileage with the same number of total engine revolutions compared to older stuff.
You also have to take into account that engine ring wear is typically the same accross all the cylinders and OP is only having a problem on the one bank which tends to make me think it could be just an issue with that cylinder head but there's the possibility that this could be the results of ring wash on that bank due to the ECM over fueling that side from a faulty 02 sensor that never got replaced and the owner just kept on driving it and can also be that the oil control rings are caked up but it's just too risky to put it all back together only to find out that it's the rings and your back to taking it apart. The engine doesn't owe you anything, it has provided many years of service so if it was me I'd be tearing it all back down and doing a rebuild.
Your assertion that high mileage means reduced power is incorrect. I have personally witnessed LS based motors make within 5HP of the same reading with over 100k miles between dyno pulls. I have seen multiple 200k mile plus engines that still show visible crosshatch in the bores, which used to be a sign that the rings were not even fully seated yet. Modern machining tolerances combined with modern oils have drastically changed the wear expectations on these engines compared to old school stuff that I grew up with. You also have to take into account that overdrive transmissions allow for much higher mileage with the same number of total engine revolutions compared to older stuff.
I agree to disagree. The cylinders may still have a cross hatch, but the ring end gaps have opened some, the valves have worn some, the cam is worn some, the pistons ring lands have worn some, the cam lobes (and cam bearings) have worn. Yes, I agree, modern machining and especially synthetic oil have made a big difference. I once had a Gen 1 SBC that had honing marks at the 100,000 mile mark. But there's more to engine wear than cylinder cross hatch marks being visible. I also agree that a 200,000 mile engine today has less wear than a 200,000 mile engine had in 1990. I once had a 3.8 Buick V6 (generally regarded as one of the longest lasting engines GM ever made) in an '03 Buick Lesabre. A deer collision finally took it off the road at 399,700 miles. Damn deer!!! It still ran good, but did it run as well as it did at 100,000 miles? No way. You also have.carbon buildup, gummy valves (thanks to GMs junk PCV system, which has sent many LS engine owners scrambling for catch cans). It all adds up, and bore wear, no matter how little, is only part of the equation.......
and to add to that list of things that DO wear out over time and then not perform as well as when new-Fuel injectors! A 200,000 mile fuel injector is *most likely* not going to be spraying as fine an atomized mist, as a new injector would/will. I had a mid-80's Corvette that I built a 383 stroker for, but reused all of the original exterior parts to include fuel injectors. The car had 167K miles on it when I did the engine rebuild. After rebuilding and installing the new 383 the engine was way down on power. I chased it throwing parts at it until I got down to the fuel injectors... I put 8 new injectors in it and the car came alive.. Like I gained 100 horsepower alive. SO... high mileage vehicles will lose power and efficiency over time for sure unless wear items are being replaced along the way. and of course O2 sensors... while they do just stop working at times and then the check engine light will alert you to the failure.. I'll bet there's a lot more of them out there that are just poorly performing and reporting false information, that the driver/owner of the vehicle is just not aware of. These things happen. If man made it-it will fail.
I agree to disagree. The cylinders may still have a cross hatch, but the ring end gaps have opened some, the valves have worn some, the cam is worn some, the pistons ring lands have worn some, the cam lobes (and cam bearings) have worn. Yes, I agree, modern machining and especially synthetic oil have made a big difference. I once had a Gen 1 SBC that had honing marks at the 100,000 mile mark. But there's more to engine wear than cylinder cross hatch marks being visible. I also agree that a 200,000 mile engine today has less wear than a 200,000 mile engine had in 1990. I once had a 3.8 Buick V6 (generally regarded as one of the longest lasting engines GM ever made) in an '03 Buick Lesabre. A deer collision finally took it off the road at 399,700 miles. Damn deer!!! It still ran good, but did it run as well as it did at 100,000 miles? No way. You also have.carbon buildup, gummy valves (thanks to GMs junk PCV system, which has sent many LS engine owners scrambling for catch cans). It all adds up, and bore wear, no matter how little, is only part of the equation.......
Your reasonably stated and well reasoned opinion has not changed mine, but I do now know that yours comes from an informed position. Since this is the internet, I feel like I am supposed to call you Hitler and tell you to **** off, but I will just say have a nice day.
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Slideshow: The controversial Ferrari F6 swaps its original flat-12 for a Corvette Z06-derived LT4 V8 and sends power to four rear wheels through a custom-built drivetrain.
7 Most Reliable High-Performance Engines GM Has Ever Built
Slideshow:These GM engines didn't just make huge power, they survived abuse, boost, track days, and six-digit mileage with a reputation for refusing to quit.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
Drivers cylinders scored, passenger perfect 
I'll also add, regardless of LS1, or LS ANYTHING going 300,000, 400,000, 500,000+ miles, there's absolutely no way that those engines are producing the same power level they did at 25,000-75,000 miles. Period. IMHO, at 250,000 miles, ANY engine could use a rebuild.....
