Clankety Clank low oil pressure (I think?)

[Spline64]

Hello all,

Sure hope someone can diagnose the sound I am hearing from my truck

First off, I did not install the current engine in the truck. Bought it with no knowledge of any work done before I got it. What I do know is they took out the 454 and hopped up a 350 with cam (not sure if rad or mild) and mounted to the existing tranny.

I am going to get a crate engine to return to 454 status in Feb (tax time whoo!) but I need your help to get there as I believe I am running on borrowed time and want to make sure I am not going in the wrong direction.

Problem:
When the engine warms up, at idle in gear when you start from a stop and give power, the engine will make a clankety sound like someone looking for their favorite iron skillet buried in an entire cupboard of the same.

What I don't get is sometimes (some days) the sound is much more pronounced then others. It also (sometimes) makes more noise when turning to the right.

I have tried different oil weights, engine treatments and such. Doesn't seem to matter. However, it will NEVER do it after initial start when cold until it is warmed up. Does clank when cold right after starting but only lasts for a couple of seconds which I can understand. I can run for a good 10 minutes before I hear it again after a start when the engine is cold.

I have replaced the the u-joints as they went bad just in case. Problem remains.

Any ideas?

thanks for the time,
Spline64

[PRattenbury]

Check your flex plate to be sure it isn't loose or cracked. Make sure your fuel pump isn't toast (if it's mechanical).

[xrcr]

Will it make this noise not in gear at idle? How about when you ramp it up sitting still? If it doesn't make the noise when you are actually moving that could eliminate internal engine issues altough things change under load.. Things loosen up when the temp. comes up so an engine noise at operating temp. can be concerning. I'd start trying to systematically eliminate things. Motor mounts tight? tranny tight to motor? tranny mount good? noise not in engine? noise in drive train? I had a flex plate that was cracked but in this case it sounded more like a throw out bearing going bad. Good Luck.

[Spline64]

Thanks for the quick responses!

Thought about the oil pump as well, may have to come to that. Fuel pump just got replaced (is electric and familiar with that sound) so that is good.

When at idle and not in gear, can't really hear anything pronounced, just the lifters and if I get down under the truck, same thing. Ramping it up doesn't seem to make more or less noise either (in park, engine hot).

Rear main seal leaks, I'd say a good 3-4 inch dia. puddle on concrete after every drive. Not sure if that helps.

Did some more testing / driving and noticed something peculiar. The sound almost goes away in reverse and immediately comes back when I go forward (engine hot). Could this have something to do with the flex plate?

thanks!
Spline64

[irishman999]

If your driving the truck and it has not thrown a rod i would say pull out your trans and check that flex plate!

[Jonboy]

It could be the flexplate. as it wears more, it will make the noise all of the time. You might be able to set the converter back enough to see where the flex plate bolts to the crank. that's where they usually crack.

[PRattenbury]

Yep, I've seen them bust the center completely out.

[Spline64]

again thanks all for the replies!! I really appreciate all the time you are all taking!!

I love it when you think you have something narrowed down only to have it change.....

Update:

Now today for the first time it made the sound in park (engine hot and only between idle and about 2000 rpm). Was about half as loud as when in drive going under 5mph. Did it in reverse as well. Much louder today then ever, thinking I need to park this beast. But again going to work this morning when it was cold, quiet and solid as a rock.

Can a mechanical oil pump make an obnoxious sound while in it's death throws? The only constant that I have now is that it only happens at low rpm and oil pressure. I don't think my gauge is working correctly as when cold is pegged over 60 psi, when hot at idle is at about 30 psi which I believe should be more than enough.

thanks all,
Spline64

[Spline64]

and another edit...noticed that when oil gets to the low on the dipstick, sometimes has bubbles on it. Thought that was only on overfilled engines but doesn't happen when at the full level.

[irishman999]

Your oil pressure gauge sounds fine, 30 pounds warm should be plenty. If it quit making the noise in reverse that kinda does sound like your flexplate.

[Spline64]

Again thanks all, I have found the problem!

While crawling under the truck looking for anything loose that could possibly be making the sound from where I was hearing it, I happened to push against my exhaust pipe where it attaches to the headers (driver side). It made a clank sound, and not just any clank sound but very close to what I hear. I looked up to try to figure out where the clank was coming from while pushing it and saw that the actual entire header was moving!! The clank was the headers hitting the head.
Got up and couldn't believe it. I was missing 4 bolts that attach the header to the head. There was a bit of carbon scouring around the area, but nothing crazy. Apparently this has been going on for at least 2 months since I last changed the plugs as the old ones didn't have any scouring on them.

Lucky for me, the bolts had simply "walked" out and I was able to put in new ones. Sound is completely gone now. I would have thought that it should have sounded like a motorboat going all out but it didn't. Is a little more quiet now but not much.

Everything makes sense now, vibration was louder when at certain rpm's cause engine was moving more, made more noise when turning to the right cause centrifugal force was pulling it from the head.

I am amazed that the bolts did this. Think that I am going to get some loctite to help them stay put.
Noticed that I had lost one on the other header as well.

thanks again all,
Spline64

[87chevy.com]

I wouldnt put lock tite on those bolts.... just screams bad idea
clint

[Spline64]

What would you do then?

[Spline64]

also, will be replacing entire engine in Feb of next year. Just want to get through half the winter.

[1malo68]

Any speed shop sells locking header bolts, summit jegs etc.

[BigBlocksRule]

When that loc-tite gets cooked in place, it's as good as a weld.
Get some locking header bolts, they're a more-better way to get 'er done.

[Spline64]

Thanks all!!
Will do

Spline64

[C low]

or you could just trow some crush gaskits and new bolts and check them every once inawile