So not sure if this is piston slap or it is something else I've had this goin on for a while pretty much since i installed motor. And at first I was convinced it was piston slap since it only happened at idle. And goes away when on load or boost. But recently I've noticed it does it still even after the piston have warmed up but once again only at idle. It starting to bother me Especially at red lights maybe someone here can let me know.first video is start up second video is after gettin it warmed up and then letting sit. The sound doesn't start immediately after warming up it takes about 20 seconds sometimes longer sitting at idle and then it will start back up. Sound does go way once past 1300 Rpms and won't hear it from there on. Sorry about second video being so dark I was outside
Engine noise
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Holy Hell!!! That sounds like a diesel engine idling!!!
Sorry I'm not able to help diagnose this one, other than it certainly sounds like an oil pressure at the lifters issue, since it quiets right down when the rpms go up and more oil pressure is sent to the lifters???
Others with FAR more knowledge about such things will chime in and help, I'm sure!!!
I'll be watching this thread to see what the final verdict is!!! Hope it ends up being something simple and low $$$ to fix!!!! -
Does it get any better when it is hot?
Hard to tell from the video but mine makes a racket until it is warm not quite that bad -
You need to find an engine stethoscope and see if its making the noise in the front of the engine (timing chain noise) or if its in the top of the engine (valve train noise) or if it can br heard from the top of the oil pan.
Let us know.
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Sounds like Polaris gave you a diesel sling.
Sent from my SAMSUNG-SM-T537A using Polaris Slingshot Forum mobile app
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I would take the valve cover off, cover everything around it and see if it is a lube issue like stated above.
Sent from my SAMSUNG-SM-T537A using Polaris Slingshot Forum mobile app
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I would personally do two things...
1. Take off the valve cover and look to see if the timing chain looks lack it has too much slack. It may be possible that someone didn't install and activate the main chain tensioner correctly. See below video at 12 minutes.
https://m.youtube.com/watch?li…rJDKIELg-po&v=evJuIsCD6Gs
2. Do a leak down test to see if one of the valves is stuck or bent.
What oil are you running? -
Display MoreI would personally do two things...
1. Take off the valve cover and look to see if the timing chain looks lack it has too much slack. It may be possible that someone didn't install and activate the main chain tensioner correctly. See below video at 12 minutes.
https://m.youtube.com/watch?li…rJDKIELg-po&v=evJuIsCD6Gs
2. Do a leak down test to see if one of the valves is stuck or bent.
What oil are you running?
Great video!
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Sounds like a solid plan. Let us know what you find
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No, you don't need to redo all of the timing. Simply watch that video to learn how to pull, reset, reinstall, and reactivate the main chain tensioner.
Its worth a try and it should take you under 30 minutes to do.
If it isn't tensioning correctly, I would think you would hear chain noise throughout the RPM range though. Not sure though...
@iNewton had some noise like this when he built his motor. Maybe he can chime in... -
Although a video will only get you so far, this sounds like piston slap to me.
Who built your engine?
You need to get the piston to bore clearance that was used to build the engine and type of material used to make the pistons (either 4032 alloy or 2618)
4032 has more silicon so less heat expansion (so tighter clearances, less piston movement. In the bore) its not as strong as 2618 which has increased strength but more expansion under heat so needs larger clearances which means more noise when engine is cold. The concept is once engine is under racing conditions the clearances will be in spec.
I have the exact same sound on mine on cold start and idle, my piston clearances are on the loose side because I intend to race it with 30/40 minutes of Wot on a very fast track and the clearances calculated where around 0.006 inches with ring gaps on the larger side. By memory stock piston clearances are around 0.0004 (yes, that is a zero more after the period, not a typo).
I have 3% blowby and 185 psi pressure in pistons on all 4 cylinders when engine cold so the sound is just an annoyance I am getting used to to have an engine that will handle 500hp at WOT for 40 minutes straight without seizing in the bore.
My engine on 1st startup after built:
What you are hearing (mecanical cause):
So this MIGHT be normal, depending on what materials used and clearances calculated by your engine builder where.
You should get a stetoscope and listen to make sure you are not in reality hearing rod knock (which means the rod bearings are destroyed and the engine is about to follow), which will come from the crankshaft area (down in the engine) vs piston slap which will come from the top of the block, just under the head).
If you suspect rod knock, you can easily check this without taking the engine apart with just a long flat screwdriver thru the sparkplug holes. I can explain how if you need or want to check this.
Don't start taking shit appart unless you know what you are looking for and confirmation the noise is not normal, you might just be causing more problems for nothing.
Keep in mind that piston slap in itself will not destroy a engine but will get worse with time to the point of needing a rebuild sooner that a piston with tighter tolerances because it will wear out the bores faster.
Again, check with your builder to see if the slap is expected or not, I was told that piston clearance above 0.003 on the LE9 would be noisy.
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I just listened again to your vids on my PC with headphones, I would check with the builder, that doesn't sound like piston slap to me, or if it is, sound way way worse than mine. My sound stops the second I touch the throttle and only reappears once engine settles on 750rpm idle, yours seams to follow rpm. I would check for rod play on the crank and check if your oil pressure is normal.
Mine also goes away completely once engine is pushed hard.
Also my engine did this since day 1, this is not a sound that appeared with time. The sound has not changed even after 2000 miles.
If your engine was silent and started doing this, it's definitely not normal and I would get it checked by the builder right away.
Anyways, my suggestion is to not take anything appart, contact your builder and let them handle this, unless you know exactly what you are doing, there is nothing you can fix with basic tools and the engine in the Sling.
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I don't recommend playing with the chain tensioning, if it was loose and skipped a tooth, the engine would run like shit, and if valves made contact with the pistons, a simple compression test will tell you valves are leaking, and at that point, you have damaged pistons and bent valves and even if you where to correct the tension, engine is still shot.
Leave everything as is and let the builder figure it out. If you start messing with stuff, its more variables the builder can use to say its not their problem.
Start with getting a spec sheet for the engine build with part numbers, clearances used for pistons, ring gaps and crank to rods bearings and bringing this sound to the builder's attention.
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