[Devz zook]

Hey guys have had some trouble on my 92 Sierra. Not long after I bought the car it seemed to make a slight nocking or ticking noise while accelerating, I was a bit concerned and thought it might be a bearing in the clutch so i took the gear box out and replaced the clutch and all bearings involved. It was fine for a while but the noise then slowly came back. I decided to carry on driving as it didn't seem to get much worse until one day driving into work the noise escalated so dramatically i had to pull over on the freeway to see what was going on.

After having a search I couldn't see anything noticeably different with the noise still there, I decided to make the call and drive home. I took the rocket cover off to find one of the tappet screws missing my original thought was that the screw had come loose and was somewhere in the engine causing damage so I have now taken the engine semi apart leaving the block sitting there.

I have been given two possibilities of what the problem could be.
1. Cracked piston skirt
2. Bottom end has gone ( assuming this means the bearing)

I don't have a lot of mechanical knowledge but learn fast. The cyclinder head is currently getting tested and shimmed does anyone have any idea on how to diagnose these two possibilities?

I look forward to hearing what you guys have to say.

Cheers

[alien]

Have you ruled out the timing set too high and it pinging?

The missing bolt might just be coincidence?

[Marko_SJ]

alien wrote:

Have you ruled out the timing set too high and it pinging?

The missing bolt might just be coincidence?

There are screws on the rocker shaft that sometimes come loose. Pretty common apparently.

I found one caught in a valve spring and ones in an oil drain from the head to the block / sump somewhere.

This knock, does it come when the car is cold, there the whole time, or when the cars hot?

[Devz zook]

Cheers for the fast replies guys,


I did the timing when I replaced the clutch, so I don't think it could be that.

Cheers marko kinda gives me a small bit of relief knowing it's pretty common. I have drained the oil and removed the sump and didn't find anything so where this screw has gone has me stumbled.

The noise is always there and seems to remain the same whether idling or driving doesn't seem to change with revs from what I remember.

I should mention this happened about 4 or 5 months ago so I might be a bit shady on the details of the noise. Time flies when your busy.

Cheers

[Devz zook]

I should also point out that I had a spare head lying around and replaced the missing screw with one from the old one so all the screws are there, weather the missing screw came loose or was lost from he previous owner is another mystery.

[Marko_SJ]

Devz zook wrote:

I should also point out that I had a spare head lying around and replaced the missing screw with one from the old one so all the screws are there, weather the missing screw came loose or was lost from he previous owner is another mystery.

Yeah, it can happen. Just loctite the new sucker in there.

Can you describe the knock a bit better, where in particular did it come from?

I'm sure if a piston was stuffed you'd really know.

Mine made like a really loud "tick tick tick" that sped up with revs when the exhaust manifold was loose. Tightened up and she went away.

Surely a bottom end knock would speed up change with revs

In anycase a "knock" makes it sound like a diesel's rattle.

[alien]

it'd be interesting to turn the motor by hand and see if you can find the tap sound then...

[Daves4wd]

Wasn't a broken rocker arm??? Valves not setting right in the head?? Maybe it's spun a bearing??.... If you pulled the motor down to a block may as we'll rebuild the bottom end while your at it.... A mate redid his head them about 4 months down the track the boo to mend went so save ya self the hassles... This is my opinion

[Devz zook]

Cheers again for the input,
It's hard to describe the sound one thing I should of done was to get a video recording of it but ohwell, it's sort of similar to a ticking/tapping noise but it's really loud and you can feel it while driving aswell sounds like something was taking a lot of damage I was cringing all the way home.

When I took the rocket cover off and found the missing screw first this was I replaced it and tested it to see if that was the issue but wasn't any different the next thing I did was search for the screw and reset all the tappets, from what I understand that is how you set the valves?

My original thought was to give a crack at rebuilding the bottom end but was told it requires a lot of mechanical knowledge and is quite difficult? Has anyone rebuilt the bottom end? There was a block that had been borne out and new pistons and everything on gumtree at the time for $200. Might have been worth buying thinking back now.

Back to my original question is there anyway or ruling out the cracked piston skirt and bottom end gone? Or do I need to pull the block out and take it apart to investigate the internals?

Cheers

[Gwagensteve]

Pull the sump. If it's a broken skirt that's where it will be.

[Devz zook]

I have the sump out and havnt seen anything in it, will there be bits and peaces if the skirt is cracked?