340 Engine Shake

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plumkrazee70 said:
I saw those update instructions, but Ive never had trouble getting the IAC to respond, so I never touched the back screw. Of course I haven't driven it either. lol. do you think the MAP reading will show something off if the seal is squished? Im worried about removing that front cover and checking it, if I don't have to, mainly due to how much is packed in there.
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Yeah, it wasn't fun digging in there. Supposedly, the MAP will read correct, but the computer sees many more updates per second than can be seen on the dashboard, and intermittent leaks at the MAP can cause issues without showing up there. Frustrating. I wouldn't dig in there unless or until you're forced to.

The reason to tweak both front/rear butterflies isn't for IAC, I think it has to do with the fuel injectors being above the butterflies. If the flies are too far closed, the fuel doesn't get past them very well and causes issues with distribution which can cause idle issues. That's a guess, but it makes sense in my pea-brain.

I know if I look down the barrels, the fuel does like to bead on the butterflies sometimes, and it makes me wonder... I do know that it's one of the reasons you don't want to rely on IAC much for idle control - it's basically a vacuum leak to vary things slightly. At idle, it can cause more of a headache than anything. It's most useful in the decel regime where we don't want manifold vac to spike too high when snapping the throttle shut (this causes the fuel to vaporize and 'dry' the manifold, which then causes a leak-spike when the throttle re-opens). That's a whole discussion on it's own, but it has nothing to do with an idle shake.
 
plumkrazee70 said:
I can see if I can track down a carb. How does the distributor react being locked out? So the weights and springs have been removed, so the efi can control the timing
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Just set it for a static 18 degrees - since so far it's an issue at idle. It'll run just fine under 3k, and be gutless above.
 
plumkrazee70 said:
I can see if I can track down a carb. How does the distributor react being locked out? So the weights and springs have been removed, so the efi can control the timing
Click to expand...

Just noticed this. How did you lock out the distributer? is it possible the top plate with the reluctor is moving? Have you checked the rotor button? If there is erratic movement here, it may be causing your problem.
 
plumkrazee70 said:
I can see if I can track down a carb. How does the distributor react being locked out? So the weights and springs have been removed, so the efi can control the timing
Click to expand...

One more question: how much idle time do you have on it so far?

Do this, go into 'large gauges' and set it to display the following:
AFR Trim
AFR Learn
IAC steps
Spark adv (I think this is the right name)

Let it warm up (above 170F) and let us know what you see for these values.
There are max limits to the learn and trim. Some engines wind up maxing out for various reasons, and that can cause issues with the system's ability to adapt at idle. There are ways to change the limits, or to even alter the base fuel so that it doesn't need to run min or max fuel trim/learn.
Spark adv should jump around a bit while it tries to stabilize the idle. You might find that the 'shake' happens when the advance increases or decreases. If so, it might make sense to increase or decrease idle timing a bit to help it smooth out. But until you can correlate which way the timing goes when the issue presents, it's hard to make a suggestion.

What are you running for fans?
Power steering?
A/C?

If any of those start drawing power, it could drag the engine down and cause issues too... something to consider.
 
plumkrazee70 said:
I can see if I can track down a carb. How does the distributor react being locked out? So the weights and springs have been removed, so the efi can control the timing
Click to expand...
Just leave it locked and set the timing to some arbitrary idle timing number. Like 20 degrees.
 
plumkrazee70 said:
Here is the engine video. (this is with the driveline removed and a slip yoke installed)

Here is the video that started it all (I believe that the driveline shake was the end result of the engine shake)
Click to expand...

The noise in the second video is severe. I seriously doubt that the engine is the cause. Something is not right almost sounds like a loose filwheel or clutch.
How does the clutch pedal feel? Does it make that noise in all gears? Find the cause of the noise and you will find the vibration issue.
So us some pic's of the spark plugs. Im old school and dont trust AFR meters to many variables.
 
I reread this thread and your original post over in the 4-speed forum. You did some mods while you had the engine out but nothing associated with the lower rotating assembly. I rebuilt a 318 for my Barracuda, I had the shop balance it. They had me bring every lower rotating part to the shop to balance the engine, including the pressure plate and flywheel. You went to a 4-speed from an auto so your flywheel and pressure plate were not balanced with the crank, rods and balancer. I know the shop drilled a lot of little divots in my pressure plate to get it to balance to the engine. I’d be suspect of the rotating assembly not being perfectly balanced. It’s really the only thing that’s changed.
 
mopardude62 said:
I reread this thread and your original post over in the 4-speed forum. You did some mods while you had the engine out but nothing associated with the lower rotating assembly. I rebuilt a 318 for my Barracuda, I had the shop balance it. They had me bring every lower rotating part to the shop to balance the engine, including the pressure plate and flywheel. You went to a 4-speed from an auto so your flywheel and pressure plate were not balanced with the crank, rods and balancer. I know the shop drilled a lot of little divots in my pressure plate to get it to balance to the engine. I’d be suspect of the rotating assembly not being perfectly balanced. It’s really the only thing that’s changed.
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Agreed
Even the change to the KB pistons would require a rebalance of the rotating assembly. IMO none of that will cause that knocking in the drive train that's in OP's video
 
AAndrews said:
Just noticed this. How did you lock out the distributer? is it possible the top plate with the reluctor is moving? Have you checked the rotor button? If there is erratic movement here, it may be causing your problem.
Click to expand...

I followed this video.

I am not sure what you mean by rotor button and what am I looking for. I checked that the balancer timing at idle (18*) matched what the efi was seeing. I then used the efi timing lock feature, which locks the timing at whatever degree you choose. In this case 30*. When that lock is enabled the efi will command 30* and then you check the balancer to be sure it is reading 30* All of that matched, so I have to assume that the motor and efi are in sync.
 
512Stroker said:
The noise in the second video is severe. I seriously doubt that the engine is the cause. Something is not right almost sounds like a loose filwheel or clutch.
How does the clutch pedal feel? Does it make that noise in all gears? Find the cause of the noise and you will find the vibration issue.
So us some pic's of the spark plugs. Im old school and dont trust AFR meters to many variables.
Click to expand...

Yes, the second video where the driveline is making a ton of noise is where this all started. It made that noise in all gears, except N. When I removed the driveline from the equation and installed a slip yoke. The noise went away and then led me to view the engine shaking, which causes the transmission to shake. Its more evident in the transmission shifter handle than anywhere.

Edit: clutch feels fine. No grinds, shifts in and out gear easy.
 
Last edited:
Phreakish said:
One more question: how much idle time do you have on it so far?

Do this, go into 'large gauges' and set it to display the following:
AFR Trim
AFR Learn
IAC steps
Spark adv (I think this is the right name)

Let it warm up (above 170F) and let us know what you see for these values.
There are max limits to the learn and trim. Some engines wind up maxing out for various reasons, and that can cause issues with the system's ability to adapt at idle. There are ways to change the limits, or to even alter the base fuel so that it doesn't need to run min or max fuel trim/learn.
Spark adv should jump around a bit while it tries to stabilize the idle. You might find that the 'shake' happens when the advance increases or decreases. If so, it might make sense to increase or decrease idle timing a bit to help it smooth out. But until you can correlate which way the timing goes when the issue presents, it's hard to make a suggestion.

What are you running for fans?
Power steering?
A/C?

If any of those start drawing power, it could drag the engine down and cause issues too... something to consider.
Click to expand...

Ok, I can make a video of those settings.

Electric Fans
AC
No PS
 
plumkrazee70 said:
Ok, I can make a video of those settings.

Electric Fans
AC
No PS
Click to expand...

I'd be tempted to pull the belts for a bit to rule out those accessories.

To echo what others have brought up, what are you using for a flywheel? I had been running a '360 balance' flywheel that turned out not to be, and same with my damper - the shake was unbearable though, and got worse as the speed increased. I did not see a shake that came and went, for what that's worth.
 
Phreakish said:
I'd be tempted to pull the belts for a bit to rule out those accessories.

To echo what others have brought up, what are you using for a flywheel? I had been running a '360 balance' flywheel that turned out not to be, and same with my damper - the shake was unbearable though, and got worse as the speed increased. I did not see a shake that came and went, for what that's worth.
Click to expand...

It's a RAM clutch and steel flywheel. They were ordered as neutral balance. I didn't notice any weights on them.

I understand the balance concerns, but lots of folks put 4 spds in after the fact and don't rebalance their cranks or am I missing something?

I'll add removing the belts to my list. I found a guy in town who is a mopar guy and has his own shop. I am going to trailer it down there he can go through all things at once. I will keep everybody updated

I appreciate everyone taking the time to chime in here. It definitely gives me a place to start.
 
plumkrazee70 said:
Here is the engine video. (this is with the driveline removed and a slip yoke installed)

Here is the video that started it all (I believe that the driveline shake was the end result of the engine shake)
Click to expand...


The first video looks like lean misfire to me since it comes and goes. Doesn't look like an engine balance problem. BTW, the way to tell between a 273/318 forged crank and a 340 is that the 340 has a hole drilled lengthwise into the front and rear crank throws. It appears that the crank has one in the front, which should mean that it has one in the rear as well.

As for the second video, is the rear of the car supported in front of the leaf springs, letting the suspension droop? If so, that can cause the noise you are hearing. the driveline angle will be off with the suspension at full droop. Put it on the ground a take a quick drive.
 
don't assume because flywheel and clutch are new that they are good and not the problem , seen new like that be a problem at a shop or 2
 
plumkrazee70 said:
It's a RAM clutch and steel flywheel. They were ordered as neutral balance. I didn't notice any weights on them.

I understand the balance concerns, but lots of folks put 4 spds in after the fact and don't rebalance their cranks or am I missing something?

I'll add removing the belts to my list. I found a guy in town who is a mopar guy and has his own shop. I am going to trailer it down there he can go through all things at once. I will keep everybody updated

I appreciate everyone taking the time to chime in here. It definitely gives me a place to start.
Click to expand...

Regarding the balance concerns: it depends. Lots of builders will balance the whole rotating assembly, and sometimes make adjustments to parts other than the crank - which is bad if you swap those parts (flex plate, balancer, etc). A good builder makes the changes to the crank - it's hard to know which way the shop did it unless you really look hard at the original flex plate or have an invoice or have it well documented some place.

More than likely your balance is good. Once I got the proper flywheel on mine, but I still had the wrong balancer, it was very noticeable. The mirrors shook at 1100rpm, the clutch pedal vibrated against the stop, it was a mess. I think you'd notice. The difference from a 360 to a magnum balancer was my issue, and that's not a huge amount of out-of-balance. I'd be shocked if a flywheel install was that far out if it was sold as neutral balance, but it does happen.

I'm still convinced it's a misfire situation due to either fuel or spark, but it's hard to say for absolute certain without being there in-person, so I could be very wrong! lol.
 
lilcuda said:
The first video looks like lean misfire to me since it comes and goes. Doesn't look like an engine balance problem. BTW, the way to tell between a 273/318 forged crank and a 340 is that the 340 has a hole drilled lengthwise into the front and rear crank throws. It appears that the crank has one in the front, which should mean that it has one in the rear as well.

As for the second video, is the rear of the car supported in front of the leaf springs, letting the suspension droop? If so, that can cause the noise you are hearing. the driveline angle will be off with the suspension at full droop. Put it on the ground a take a quick drive.
Click to expand...

The rea was supported by both the axle and the frame and it didn't seem to make a difference.
 
I decided to post these. I'm not saying this is the problem, but you can see the various places this 340 crank was drilled for the internal balance.

20220815_184542.jpg


20220815_184549.jpg


20220815_184614.jpg


20220815_184628.jpg


20220815_184633.jpg


20220815_184636.jpg
 
Alright everyone. Check this out



I started it up on the ground with the driveline back in and sure enough, the driveline sound is gone... I was going to take a quick spin around the block, but gun shy when I noticed the oil pressure gauge. To be honest, I've been so focused on the motor, Fitech settings etc, I didn't notice this before. It sure seems it is falling right when the surge happens. Thoughts??
 
plumkrazee70 said:
Alright everyone. Check this out



I started it up on the ground with the driveline back in and sure enough, the driveline sound is gone... I was going to take a quick spin around the block, but gun shy when I noticed the oil pressure gauge. To be honest, I've been so focused on the motor, Fitech settings etc, I didn't notice this before. It sure seems it is falling right when the surge happens. Thoughts??
Click to expand...


What kind of gauge is that? Electric sender? A bad ground, or power, or something along those lines could definitely cause weak spark, changed in timing, etc.
 
Phreakish said:
What kind of gauge is that? Electric sender? A bad ground, or power, or something along those lines could definitely cause weak spark, changed in timing, etc.
Click to expand...

It's a speed hut electric. I thought that also, but all the Guages are daisy chained together with their harness. They get one power and one ground and I'm. It experiencing any other Guages fluctuate like that. (I would think if it's a voltage issue, I would see it elsewhere) I'm getting 14v at idle. I was wondering if something could be a wrong with the oil pump drive or dist. shaft?
 
FIRST thing to do is get a manual oil pressure gauge and replace that one and see if it does the same thing. If it does you have bearing issues.
 
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