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More engine sounds at low rpm

kidmet

Supporting Member
219
20
Jul 23, 2012
Aurora, Colorado
Since you guys helped me so much on my last engine noise. How about this one. Sounds almost like a diesel at low RPMs and would die if i don't give it gas, before it warms to idle. Is fine over 1k rpms and when warm.
 

kidmet

Supporting Member
219
20
Jul 23, 2012
Aurora, Colorado
Assuming the valve timing is set properly. What's the history of the noise? Does this noise just start to occur? or You have it from before? To me, it sounds like extreme piston slap.
Son of a. That's what I was worried about. It's basically always been there. This engine has maybe 5 miles on it and some idle time. Built a couple years ago, but never ran it. I have a picture from when I took the head off that shows some uneven wear marks in the cylinder. You can see on the 1 and 4 cylinder at the top, there are wear marks.
 

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DSMPT

DSM Wiseman
1,358
900
Jun 12, 2014
Japan / Mexico, Arizona
I don't want to lose sight on the issue, but if it's piston slap, what can I salvage from this block?

Crank? Rods? I'd assume pistons and block would need replaced.
Assuming this is piston slap. Do you have a spec sheet or remember what piston to wall clearance the engine builder put?
In general, a stroker engine has more obvious piston slap sound than a standard stroke engine, that's why I asked you if it's a stroker engine or not. It's hard to tell how loud is actually bad, because it would depend on the piston to wall clearance, piston skirt design, material, with or without skirt coating etc etc.
So you have piston slap doesn't always means something actually bad right now. If your engine is a stroker and built with loose clearance, you would hear more slap sound is normal. As long as the slap sound is gone when the engine gets hot, I wouldn't be worried too much. But I can't tell if it's 100% safe since I don't know how actually the engine is built. Just do a compression test and leak down test, and avoid to rev up until the engine gets warm, and do not have the idle too low like in the video. The RPM when the loudest noise is occurring in the video seems to be too low. And as you mentioned that the engine stalls, that's probably not directly caused by piston slap. I guess it's caused by tuning issue or something else.

And if this is piston slap, there is no direct solution for this without rebuilding, since the engine is built in this way. Maybe you can try higher viscosity oil, this may reduce the noise a bit.

The wear marks on cylinder wall in the pic are normally found more often on a stroker engine, actually not that special. But also that's the reason why some people don't recommend a stroker. Because the cylinders would possibly end up going oval by time. And the piston's life span would be shorter since the piston skirt rocks harder than usual. But it doesn't mean you can't run. This is kinda common thing on a stroker engine.
 

kidmet

Supporting Member
219
20
Jul 23, 2012
Aurora, Colorado
Makes sense. I've been sourcing parts to build a new engine and my builder saw and reached out. I think he's going to take a look and also tune it for me. Pretty pleased he reached out. The tune on this is basically nonexistent (basic setup in ecmlink is done as far as injectors and such, but not dialed in), so tuning issues are definitely there.



Assuming this is piston slap. Do you have a spec sheet or remember what piston to wall clearance the engine builder put?
In general, a stroker engine has more obvious piston slap sound than a standard stroke engine, that's why I asked you if it's a stroker engine or not. It's hard to tell how loud is actually bad, because it would depend on the piston to wall clearance, piston skirt design, material, with or without skirt coating etc etc.
So you have piston slap doesn't always means something actually bad right now. If your engine is a stroker and built with loose clearance, you would hear more slap sound is normal. As long as the slap sound is gone when the engine gets hot, I wouldn't be worried too much. But I can't tell if it's 100% safe since I don't know how actually the engine is built. Just do a compression test and leak down test, and avoid to rev up until the engine gets warm, and do not have the idle too low like in the video. The RPM when the loudest noise is occurring in the video seems to be too low. And as you mentioned that the engine stalls, that's probably not directly caused by piston slap. I guess it's caused by tuning issue or something else.

And if this is piston slap, there is no direct solution for this without rebuilding, since the engine is built in this way. Maybe you can try higher viscosity oil, this may reduce the noise a bit.

The wear marks on cylinder wall in the pic are normally found more often on a stroker engine, actually not that special. But also that's the reason why some people don't recommend a stroker. Because the cylinders would possibly end up going oval by time. And the piston's life span would be shorter since the piston skirt rocks harder than usual. But it doesn't mean you can't run. This is kinda common thing on a stroker engine.
 

biglady112

Proven Member
1,726
268
May 20, 2004
Commerce City, Colorado
I spent 13 hours going through this car today. Among the many issues I found, no offense Sean, this turned out it was both the flex plate and torque converter bolts had come loose. I have it running very well now and will be tuning it tomorrow. I am also putting it on the Dyno on Monday as well

The motor is in good health and finally ready to play. I mean, I only built it three years ago.
 

DSMPT

DSM Wiseman
1,358
900
Jun 12, 2014
Japan / Mexico, Arizona
I spent 13 hours going through this car today. Among the many issues I found, no offense Sean, this turned out it was both the flex plate and torque converter bolts had come loose. I have it running very well now and will be tuning it tomorrow. I am also putting it on the Dyno on Monday as well

The motor is in good health and finally ready to play. I mean, I only built it three years ago.
I have already pointed that issue in his another post and thought he has already fixed it. So it hasn't been fixed or what? I don't get the situation..
 

biglady112

Proven Member
1,726
268
May 20, 2004
Commerce City, Colorado
I didn’t ask Sean if he attempted to repair it.

As stated, I spent 13 hours going through the car front to back today. It is now fixed. I will be tuning the car tomorrow.
 
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