Leak down blues on low mileage take out LS3
02-10-2018, 01:06 AM
#1
Leak down blues on low mileage take out LS3 So this is my second LS3 from the same supplier who claims this particular engine has 900 miles in it. The Oil pan has zero sludge in it and I was the first to remove the pan. It still was RTV'd on the front and rear cover transition areas and the bolts heads had no tell tale signs of ever being touched.
The leak down numbers are done with the two gauge PSI variety. Testing was done with 50psi as the introduction number. I found 2 intake valves leaking by. One was corrected by removing that particular rocker and tapping on the stem with a plastic hammer. The second intake valve seems to be held open by the rocker/lifter/cam. Almost like the lifter won't take preload???? Every time I reinstall that rocker the valve opens. I've tried rotating crank 180deg with same results? I also have 3 other cylinders leaking by rings bad about 40%. My first question is if the engine was hot what type of increase should I see in my testing (if any)? Talking about the Rings at this point. Yet to do a compression check, I didn't have my oil pick up/pan In place . My second question is if I heat oil pan to 200 or so degrees with oil in pan the roll motor over with starter to emulate a warm motor does that method put enough heat on it? I'll post leak down numbers and compression numbers tomorrow.
thanks
The leak down numbers are done with the two gauge PSI variety. Testing was done with 50psi as the introduction number. I found 2 intake valves leaking by. One was corrected by removing that particular rocker and tapping on the stem with a plastic hammer. The second intake valve seems to be held open by the rocker/lifter/cam. Almost like the lifter won't take preload???? Every time I reinstall that rocker the valve opens. I've tried rotating crank 180deg with same results? I also have 3 other cylinders leaking by rings bad about 40%. My first question is if the engine was hot what type of increase should I see in my testing (if any)? Talking about the Rings at this point. Yet to do a compression check, I didn't have my oil pick up/pan In place . My second question is if I heat oil pan to 200 or so degrees with oil in pan the roll motor over with starter to emulate a warm motor does that method put enough heat on it? I'll post leak down numbers and compression numbers tomorrow.
thanks
02-10-2018, 01:29 AM
#2
Heating the oil will do nothing, The reason having the engine warm makes a difference is because as metal get warmer it expands. This is why you can have piston slap when an engine is cold and it will go away once it warm. There is also the difference in metal, Different types of metal expands at a different rate.
02-10-2018, 07:14 AM
#3
Heating the oil will do nothing, The reason having the engine warm makes a difference is because as metal get warmer it expands. This is why you can have piston slap when an engine is cold and it will go away once it warm. There is also the difference in metal, Different types of metal expands at a different rate.
02-10-2018, 08:01 PM
#6
When engines sit I think their valve get stuck/muck, old hard carbon becomes even older and harder. I had this experience when compression testing JY engines. I tested around 10 engines and all of them had poor compression on some cylinders. I started seeing a trend. I took a couple home and found nothing wrong with either; A cleaned up set of heads and gaskets was all it took to bring it back to perfect. I also took the time to de-carbon the pistons (brass brush + mineral spirits)
I've seen the same thing with imported engines that sat long time also, but not as bad. I think those motors tend to have lower mileage. Also anything with it's pcv system removed or disabled was always extremely filthy, best to avoid those.
I've seen the same thing with imported engines that sat long time also, but not as bad. I think those motors tend to have lower mileage. Also anything with it's pcv system removed or disabled was always extremely filthy, best to avoid those.
02-10-2018, 08:14 PM
#7
When engines sit I think their valve get stuck/muck, old hard carbon becomes even older and harder. I had this experience when compression testing JY engines. I tested around 10 engines and all of them had poor compression on some cylinders. I started seeing a trend. I took a couple home and found nothing wrong with either; A cleaned up set of heads and gaskets was all it took to bring it back to perfect. I also took the time to de-carbon the pistons (brass brush + mineral spirits)
I've seen the same thing with imported engines that sat long time also, but not as bad. I think those motors tend to have lower mileage. Also anything with it's pcv system removed or disabled was always extremely filthy, best to avoid those.
I've seen the same thing with imported engines that sat long time also, but not as bad. I think those motors tend to have lower mileage. Also anything with it's pcv system removed or disabled was always extremely filthy, best to avoid those.
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02-10-2018, 10:19 PM
#8
oh man. The only way I would ever consider not removing a JY engine head is if I could run it in the vehicle, get good compression in the vehicle, and pull every exhaust stud loose. Its about $25/stud to remove so a $1000 low mileage engine quickly becomes a $1200+ once you start snapping those studs.
02-11-2018, 09:23 AM
#9
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If you do pull the heads, I suspect a quick valve lapping will cure any valve seat related leaks. As to the lifters, I got a almost brand new set of LS7 lifters and trays. You might be able to recover that stuck lifter by soaking in ATF - its like the best detergent ever. Tide would be jealous.
02-11-2018, 10:16 AM
#10
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02-11-2018, 05:06 PM
#13
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Frank, is this data taken from dry cylinders, meaning you have not put any fuel, WD-40, oil, or anything in them?
02-11-2018, 05:14 PM
#14
Upon receiving engine it was liberally lubricated on top as well as below the Rings prior to rolling engine over by hand. Once the oil pick up tube and pan was in place for my application I filled the sump and filter . I also back fed the system with through the oil pressure sending unit with about 1/2 quart of oil. Once oil was pushing out of the oil sending unit tower I started with the compression checks. I ran them for the most part dry meaning no additional oil was pumped into spark plug hole. I did roll this engine over with the starter a boat load of times both dry and wet to try to get numbers to jump to varify the Rings. Both leak down and compression numbers were not administered bone dry like would be on a warm engine. But the test numbers recorded were with no additional oil unless noted.
02-11-2018, 08:17 PM
#15
ModSquad
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Upon receiving engine it was liberally lubricated on top as well as below the Rings prior to rolling engine over by hand. Once the oil pick up tube and pan was in place for my application I filled the sump and filter . I also back fed the system with through the oil pressure sending unit with about 1/2 quart of oil. Once oil was pushing out of the oil sending unit tower I started with the compression checks. I ran them for the most part dry meaning no additional oil was pumped into spark plug hole. I did roll this engine over with the starter a boat load of times both dry and wet to try to get numbers to jump to varify the Rings. Both leak down and compression numbers were not administered bone dry like would be on a warm engine. But the test numbers recorded were with no additional oil unless noted.
I have to say that I believe I’d take this one back as well, unless your willing to take it apart and diagnose what’s actually wrong. Not what you’d want to hear, but just telling you what I’d do.
Are these pullouts from accident vehicles, or dealership pullouts due to warranty issues?
02-11-2018, 08:23 PM
#16
I don't want to divulge the sellers business at this time. They still have my 4+grand. They are low mileage units(under 1000 mile) removed in favor for a LSX blower motor. That's what I was told.
02-11-2018, 08:33 PM
#17
ModSquad
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For $4k plus, you could get into a nice engine, without issues. I’ve got one for sale, and I also have a guy who I buy a lot of pullouts from. He’s one of the largest movers of LS pullouts in the country. Pm me if your interested.
02-12-2018, 10:20 AM
#19
I'm confused by your numbers. Like cylinder #7 what does 245 lost 220 oiled 235 mean exactly?
On the leak down test are you 100% certain the you have the piston at TDC and turning the engine to bring each cylinder being tested to TDC?
On the leak down test are you 100% certain the you have the piston at TDC and turning the engine to bring each cylinder being tested to TDC?
Last edited by LLLosingit; 02-12-2018 at 10:25 AM.