Engine vibration/knock on engine slowing

[Boomdeeze]

I have done many tests and checking and have not found anything that would cause this..

My car runs great but when I rev the engine up and let off, there is a small vibration/knock right when it gets backs near idle. When the car is idling, you can hear a the slight tick from under the engine. It does sound like it is coming from the pan area or right by the rear seal area. When the engine is revved up and it is going back down to idle, the vibration comes at about 1300 rpms and stops right before it idles at 1000.

The block is a 6 bolt with Pauter I beams, Wiesco HD, Kiggle main girdle, L19s. I just went through everything and it all looked great when it was out. Will be running 32-35 psi on the HTA76. It is an automatic with a ratchet shifter. Kiggly 6 bolt in a 2g kit, Sinister TC, ARP TC bolts(still tight).

I performed a compression test which is 164(1), 180(2), 180(3), 180(4). I have always had lower compression in cylinder 1. Just redid the head which brought them all up. Car idles perfectly at 1000, revs great and sounds strong, no knock or rattle, it only happens on decel/engine slowing. Car has 14-15 -inHG at idle with Kelford 264/264.

Anyone ever had this or have an idea of what to check? Would you run it? I have not driven it yet as the roads in MN are still covered in salt.

 

[jakk220]

Possible that the harmonic balancer is starting to separate? If it sounds like its coming from near the transmission area there is a chance it could be the intermediate shaft bearing maybe. I assume you do not have balance shafts?

 

[Boomdeeze]

The balance shafts are deleted with the GSC Power Division Race Balance Shaft and I times it when I did the timing belt. The timing is spot on. I also have a fluidampr installed.

 

[A Sharp]

Is your exhaust sitting too close to something? It could be rattling when the harmonics are just right.

Also is your car a manual? If so, what clutch and flywheel do you have? I know that some clutch/flywheel/TOB combos can make noise, which is an issue on my car (it has a slight rattle at idle). When I hold the clutch in, the noise goes away.

Don't be afraid to get a stethoscope either. They're dirt cheap and very useful.

 

[donniekak]

Check your converter bolts.

 

[A Sharp]

Missed the part where you said automatic. Durr.

 

[Bleakley]

Check your converter bolts.

^^^THIS^^^
I was about to say check flywheel bolts! Then I saw this comment and reread the mods.

 

[Boomdeeze]

The converter bolts are tight. I am not going to try and retourque them as I used red locktite and don't want to break that stuff loose(If possible).

I think it may be the pilot bearing. When I had the engine out, I was able to insert and remove the pilot bearing by hand and it slid in/out fairly easily. I am guess it vibrates on decel and is causing this.

 

[Bleakley]

I don't have that much experience with DSM's, but Nissan's you should def not be able to remove that by hand. Lol.

 

[Boomdeeze]

In reality, I don't see the point of it. The TC is held in place by the TC bolts so what is the point of the pilot bearing, to initially line it up?

 

[Bleakley]

Pretty sure it prevents deflection? (Right word) of the input shaft of the transmission. Basically supposed to help prevent it from wandering.
Without it, transmission damage can result (I think starting with bearings).

I'm a little fuzzy, but I'm pretty sure that's the reason. I read up on em a WHILE ago... Anyone feel free to correct any misinfo or concur. Lol.