1986 Vette

Hello!

I recently bought a 1986 Corvette in need of some TLC. I replaced the half shafts this weekend and took the car for a test drive, it felt really good initially and then a loud knock and squeal began emanating from the engine. I was rather close to home so I shifted to neutral and coasted back to the house. I started it once to record the sound and uploaded it to youtube. I was hoping that someone might be able to give me some feedback/ potential diagnosis before I decide to yank the 350 and attempt a rebuild. Thank you in advance, below is the link to the video, sound is clear around 8 seconds in.

http://www.youtube.com/watch?v=0_2nD...ature=youtu.be

Regards,

Chris

ejscarfo

That doesn't sound good, at least from the little bit you posted. Did you take the belt off the see if the sound was still there?

1986 Vette

ejscarfo,

Not yet, that is the next step for the squeal, I was concerned about running the engine anymore than I absolutely have to in order to prevent further damage if possible. I will remove the serp belt tonight and give it another shot, and try to get a longer video of the sound in the process if possible. Thanks for the quick reply.

Regards,

Chris

leesvet

yeah, pull the belt off to be sure.
Did you notice what the oil pressure was doing?

That's a big end rod bearing....the squeal...possibly bearing, possible coincidence.
May have spun a bearing. if so, the OP should be near gone with most gushing out of that wounded bearing..

1986 Vette

leesvet,

I wish I had an answer for the OP reading, right before the knock and squeal issue began, my dash ground whet out and only my high beams and blinker lights were illuminated very bright, and consequently I was unable to read my gauges. I noticed a new weeping oil leak around cyl 1 on the valve cover when I opened the hood after the incident, perhaps this is related?

Thanks for the insight, I really appreciate all thoughts and experience.

Regards,

Chris

1986 Vette

Alright, just got home and pulled the serp. belt. The squeal seems to be the alternator pulley as when I moved it by hand it recreated the squeal, and after running the engine only the knock returned. I uploaded a second video, this time without the serp belt, and I re-soldered the cluster grounds so I could monitor the OP. Sitting right around the mid 40's or so. Please take a look at the new link below, any suggestions are indeed welcome. Thanks!

https://www.youtube.com/watch?v=3UwI...ature=youtu.be

John A. Marker

Pull the valve covers and look to see if you have a rocker arm that has come off. It sounds like your throwing a push rod up and hitting the cover. I had a rocker arm stud break off on my AFR heads and the sound was similar. Does the sound appear to be one one side. Pull that cover first.

1986 Vette

John,

I pulled the Left valve cover,as this was the one where I believed the noise was comming from, no signs of rocker arm detachment or damage, the valve cover is cracked around one of the setting bolts, and the seal is cracked and brittle, will order replacements while I am here, thought I feel it is safe to say these issues would not be causing the knock. Pulled the Right valve cover and still no obvious signs damage, seal looked better and the valve cover was fully intact, will probably end up replacing it as well while I am here.

Here are the images of the rockers and push rods. Further thoughts?

Thanks!

http://postimg.org/gallery/28777cdq/

hooked073

#2 cyl. first rocker looks like it has hit something. very hard to tell by the pictures.

1986 Vette

Hooked073,

I did not notice that until you pointed it out, looking at the picture it does seem that way. I will have to further inspect that when I get home to ensure that it is not just a trick of the light and low quality photo. Thank you for the suggestion!

John A. Marker

For the sound it was making, I would expect to see the rocker arm off the rod and valve. Are all the rocker arms snug? No excessive play side to side which might indicate a bent push rod? Your sure the sound is on the passenger side? If you pull the other cover off and find nothing. Then unfortunately it has to e internal. You could then jack up the front of the car, block the wheels and place the front end on jack stands and pull the pan and see what you can find.

1986 Vette

John,

I pulled both valve covers and inspected the rockers and push rods on each side. All of the rocker arms were snug with minimal play side to side, no clear and obvious signs of wear or damage. Although I am certainly not an expert, I could see nothing that would be moving enough to cause that knock. Dropping the oil pan is next on the list to see if it is a loose connecting rod, or something along those lines.

I posted a few pictures of the valve covers removed at this link here:

http://postimg.org/gallery/28777cdq/

Unfortunately they are not the highest quality pictures and therefore difficult to properly analyze. Thanks again, I am grateful for the input. I really want to exhaust all possible options prior to resorting to pulling the engine and conducting a more thorough investigation.

John A. Marker

I looked at the pictures, but sometimes they do not tell the story. Which is why I asked if any were loose.

I feel your pain at the moment. It does not look good at this point.

1986 Vette

Sure thing, I sure was hoping to find something obvious, however it appears as though I was not that lucky. I have a friend with a cherry picker and an engine stand who said I could use them, and I get the feeling that if I do need to pull it I will be learning quite a bit in the process! I will keep updating as the diagnosis proceeds, and thanks again for the help!

ejscarfo

Thanks for posting that second video. The knock is loud, sounds like a rod knock to me. Did you run the engine with the valve covers off to check movement of the rocker arms? The knock may be coming from a worn cam. From the looks of the pictures, it looks to be a high mileage engine, correct?

1986 Vette

ejscarfo,

Yeah, the second video is a lot more helpful to demonstrate the noise. I have not ran the engine without the covers, I was slightly apprehensive about trying this as I had to disconnect the injectors and plugs to get the cover off, and was not sure what the exact procedure for doing this was (what needs to be connected and what is alright to be left off). I will do some further research, connect up the wires, and injectors and give it a shot, anything in particular I should be looking for during the test, or just try to get in close enough to hear where the knock is originating from?

As far as the engine mileage, it has a bit over 104k on the engine, and had been sitting for a while before I acquired it.

Regards!

ejscarfo

There really is no need to disconnect the injectors when removing the valve covers, they should come off easily, especially the right side.

Anyway, reconnect everything and leave the covers off. With them off you can get a better idea where the noise is coming from. If its on the valve train, you can hear it clearly. Check to see each valve/rocker arm is moving. If one is standing still, you may have a collapsed lifter. The noise also seemed a little tinny. It could be your timing chain skipped a tooth or two and the valves are hitting the pistons. See if the timing is off using a timing light and following the correct procedures (car in Park or Neutral, connector unplugged, etc.).

1986 Vette

The rail that the wires for the injectors, MAF sensor, etc. were routed through did not allow enough room for the cover to pass, perhaps someone installed theses different than the original stock design, or perhaps I was just doing something wrong(more likely Alright I am going to give that a shot, and like last time I will try to shoot a video of the results for analyzing. Again, thank you.

1986 Vette

Alright, so I reconnected all the injectors, wires, and plugs; then ran the engine with the valve covers off, the sound was much more audible on the drivers side than on the passengers side. All rockers rods and valves seemed to be moving, so it does not look like the collapsed lifter issue. Still sounds deeper to me....I have a friend who is going to let me borrow his timing light and I will try to see if that is causing the problem next.

Here is the video of the most recent test, sorry it is a bit fast on the drivers side, I think its my lack of experience but these things tend to make me a bit nervous! Thanks for the help I am grateful for the assistance and being pointed in the right direction.

https://www.youtube.com/watch?v=75L8...ature=youtu.be

l98tpi

That sound makes me cringe. I hate to be the bearer of bad news, but that squeal is the same one I heard when my engine spun bearings. It sucks.