Engine/Cabin Vibration

[TripleC321]

14 minutes ago, Ronnie said:

No, it just doesn't sound right to me in the video. Does it accelerate and run smooth on the highway?

Yes it does, completely. No loss of power (that I can tell. If there is loss of power, it’s consistent across the RPM band), no stuttering, nothing. (Sometimes I think I hear a slight stutter upon a cold start, but that’s a maybe)

 

runs completely fine at highway speed. Just considerable vibration upon initial shift to 4th gear, as 4 gear hits at 45 MPH and subsequently drops RPM to 1400 which is when the vibration is prevalent. 
 

outside of 900-1400 RPM I notice nothing out of the ordinary really. 

[2seater]

So, my crude math says vibration is at 1/10 of engine rpm ? I can't imagine what would be moving at that frequency. The closest would be one cylinder firing at 1/12 the rpm? Balancer and flexplate are engine rpm. Balance shaft runs from cam shaft but is geared  up at two to one so it is engine speed also. I am far from an expert in these things, but it would seem to point to a harmonic. I don' understand the narrow band.

[2seater]

The other things that turn are generally more than engine rpm due to pulley ratios, so I just don't know.

[Ronnie]

I'm stumped. I've ran out of things to try. 

[Ohjai]

When I was having serious vibrations issues with my 38 Cadillac I searched the web.  What i found was Weber Auto at Weber State University.  They have excellent videos on many subjects.  Included was the video below on the NVH (Noise-Vibration-Harshness) App for both iPhone and Android phones.  It is now $99.00 to download. It was much higher when I purchased it.  It helped somewhat but difficult for me because of short term memory issues. 

 

This app uses the sensors in your phone to measure the vibrations.  You input the various ratios of the rotating components of your car, (transmission/drive shaft, rear end, tires) then road test the car and see what is vibrating.  One of the features I found interesting is you measure the engine vibration directly on the engine, then place the phone on the chassis to see how well your engine/transmission/body mounts are doing.

 

If your not familiar with NVH, watch some of the other video's, there is a bunch to choose from.

 

Jim

 

https://www.youtube.com/@WeberAuto/videos

 

 

 

 

 

 

[2seater]

This is a photo of the flywheel/flex plate. You can see a large flat weight welded on at about 12 o’clock, right above the two moon shaped cutouts. It is on the side toward the block. Any chance the weight has removed itself somehow? It was mentioned it was a replacement part.

 

I know the ignition has been replaced for the most part, but looking at the non operational new parts Alchemy has had, is the chance of a misfire still present?

[DAVES89]

I've got the flywheel from my engine rebuild. Cost of freight or free pick up [for you 2seater].

[TripleC321]

8 hours ago, 2seater said:

This is a photo of the flywheel/flex plate. You can see a large flat weight welded on at about 12 o’clock, right above the two moon shaped cutouts. It is on the side toward the block. Any chance the weight has removed itself somehow? It was mentioned it was a replacement part.

 

I know the ignition has been replaced for the most part, but looking at the non operational new parts Alchemy has had, is the chance of a misfire still present?

Maybe? Everything on the original flywheel was very very stuck on there. Nothing was cracked or loose. 
 

just reused the original engine flywheel on the new engine. 

[TripleC321]

I took it to another mechanic. They came back with the following:

 

1) passenger rear transmission mount is bad because oil and trans fluid leak wage on it has caused it to degrade. (I replaced that mount a year ago. Does oil on it cause degradation?)

 

2) the engine is unbalanced because the “motor mounts aren’t centered.” He said the engine needed to be adjusted so it was centered on the mounts. However as we all know those mounts only bolt in in 1 spot. He may be picking up on my sub frame being out of alignment. Cause I did goof the sub frame alignment when I replaced the sub frame bushings. Would that cause the vibration?

[DAVES89]

Oil does cause degradation and yes the subframe mounts can make a difference.

[TripleC321]

2 minutes ago, DAVES89 said:

Oil does cause degradation and yes the subframe mounts can make a difference.

How much degradation does oil cause in only a year? It’s not a large leak, just a little bit from the valve covers. 
 

and does the sub frame being out of alignment a little bit, but all 6 bushings make full contact, cause that?

[2seater]

There isn't any good way to answer those two questions.

Yes, petroleum products do degrade rubber over time, usually causing swelling and softens the rubber compound. That said, a year seems like a very short time for major damage to occur. I am not sure if different types of fluid, such as transmission or power steering would be more aggressive or not. The person on the spot is the best judge.

How can the subframe be out of alignment and more importantly, how to improve the alignment? I can see if everything is in a sort of bind and is not free to float in a neutral position, more vibration can be transmitted to other parts. Do they have a suggestion?

[Ronnie]

1 hour ago, TripleC321 said:

Cause I did goof the sub frame alignment when I replaced the sub frame bushings.

If there is any metal to metal contact between the subframe and the body that would transfer engine vibration inside the car. I really don't think the transmission mount is the problem unless it is somehow making metal to metal contact.

[TripleC321]

Their suggestion is to undo all the motor mounts, lift the engine a bit, then allow it to settle back down. 
 

they think the mounts might not be making even contact. 

[TripleC321]

mechanic called. Readjusting motor mounts didn’t help. 
 

they now think the balance shaft is out of time, maybe potentially damaged. 
 

after everything that’s been checked I wonder if the balance shaft is the culprit too. However, I find it implausible it’s damaged. If the balance shaft got damaged, I’d have much bigger problems. 
 

It being out of time however, I could see that having happened since someone opened up the timing cover before me. 

[Ronnie]

24 minutes ago, TripleC321 said:

I could see that having happened since someone opened up the timing cover before me. 

This thread is getting long so this might have already been covered and I've forgot... Has it always vibrated since you've owned it or did it just start suddenly after you got it? Or could it have started when you opened up the timing cover as you seem to say you did?

[2seater]

I didn't see any word on the subframe issue? My thinking would be similar to the motor mounts. Loosen all six bolts, jack under the rocker panel jacking points enough start to let the suspension drop (not off the ground) and then set it down and retorque them.
 

Interesting the balance shaft comes up now and then. The only plausible way for that to happen is if the timing chain set was changed at some point and they indexed the balance shaft incorrectly. The gear behind the cam sprocket only goes on one way but the balance shaft itself can be spun to any position if the gear is removed.

[TripleC321]

10 minutes ago, Ronnie said:

This thread is getting long so this might have already been covered and I've forgot... Has it always vibrated since you've owned it or did it just start suddenly after you got it? Or could it have started when you opened up the timing cover as you seem to say you did?

I replaced the original engine with a used one as the old engine died. 
 

The previous owners of this engine had opened the timing cover before I acquired it. 

[TripleC321]

14 minutes ago, 2seater said:

I didn't see any word on the subframe issue? My thinking would be similar to the motor mounts. Loosen all six bolts, jack under the rocker panel jacking points enough start to let the suspension drop (not off the ground) and then set it down and retorque them.

The mechanic just did that and didn’t notice any change. 

[TripleC321]

Posting here for future knowledge: 

 

the issue was in fact the harmonic balancer. My Handiman said the old one looked like it had been “beat on with a hammer.”

 

replacing the balancer did fix the issue. 
 

I guess the moral of the story, is if you have a weird engine vibration you can't track down, it might be the balancer. Even if you don’t have the usual sound that occurs with a bad balancer.