396 big block knock after warmup

[1stgen68]

I’ve posted a few things this week because I have a few issues to this new to me 68 SS clone. After the engine warms up there is a faint knock and I cannot tell where it is coming from being the top end or bottom end. Almost sounds like something is knocking against something somewhere. I was going to post the video on YouTube but I’ve found that the resources on this forum are more valuable and I respect the responses from people that know way more than me about these 1st gens and engines. If anyone wants. I can e-mail this video to someone.

[maroman]

solid or hydraulic lifters?

[1stgen68]

I really don’t know what type of lifters are in it

[bertfam]

Once the car warms up and starts to knock, disconnect all the belts and see if the knock goes away. But DON'T run it too long or it'll overheat. Just long enough to see if the knock stays or goes.

I had a bad water pump once that sounded exactly like rod knock and luckily, before I pulled the engine, I tried this trick. Saved me a TON of money and time!!

Ed

[1stgen68]

That's a great idea Ed!!

[adjudimo]

Also, you might pick up a stethoscope from your local car parts dealer to see if you can isolate the noise. They don't cost very much and work like the ones doctors use to listen to your ticker. LOL

[x66 714]

I had a p/s pulley rocking on the p/s pump because of powder coating....Joe

[1stgen68]

So i came across some youtube videos regarding water pump knocking due to bearings going bad and the knock that it makes is exactly like the knock i'm having which give me hope.

[bcmiller]

I’ve posted a few things this week because I have a few issues to this new to me 68 SS clone. After the engine warms up there is a faint knock and I cannot tell where it is coming from being the top end or bottom end. Almost sounds like something is knocking against something somewhere. I was going to post the video on YouTube but I’ve found that the resources on this forum are more valuable and I respect the responses from people that know way more than me about these 1st gens and engines. If anyone wants. I can e-mail this video to someone.

You could still post the video to youtube, then we could hear what it sounds like.  Good luck.

[1stgen68]

I went ahead and did that last night. Sounds exactly like a water pump woble or bearing going out.

https://youtu.be/YopLO-cNMTY

[bcmiller]

Sounds right for that that issue.

[bertfam]

To me that sounds more like something hitting sheet metal or similar. A water pump knock is more of a dull thud.

Pull the belt just to make sure, but I have a feeling the knock will still be there. If it is, feel the valve covers. If it's the rockers hitting the covers, you should be able to feel it.

Ed

[1stgen68]

Ed, i was telling someone the same thing!! Sounds like the headers or something banging against something but it only does it when the engine start to warm up. I'll pull the belts and see how it goes.

[L78racer]

could be a bad fuel pump.

[bcmiller]

It seems too intermittent to be a rocker arm, in my opinion.

Is it louder on one side? Louder in front?

Could be a bad or loose pulley.