metallic rattle quiz

[silvadw]

driving casually home, mild acceleration.....suddenly a metallic rattle from the engine. the wider the throttle, the louder and more ugly the sound. Haven't had time to diagnose. Before this, the car was running quite well.
Now the quiz.....
1) busted valve
2) blown exhaust gasket
3) something expensive to do with a piston
4) something came loose in the carb (34ADF) and got sucked into cylinder
Depending on where you live and my ability to get there, there may be a prize for the first correct entry

i will also tally votes and provide the answer when i find out.

[azruss]

I assume the rattle times with engine RPMs

[silvadw]

I assume the rattle times with engine RPMs

Yes Azruss, rattle times with revs, and there is no coolant in the engine oil

[131]

At engine RPM, or half? What's it like at idle? What air cleaner are you running? Not entirely uncommon for the air cleaner studs to be stripped out of the top of the carb, they work free and get ingested.

[burgandy81]

I have chased a lot of rattles on my spider and have found it best to check the simple things first.

Heat sheild on exhaust manifold
Sheet metal around rad
Nuts and bolts on intake and head

Start with a "percussion inspection" open the hood and gently tap or bang on everything and anything you can see. Use your gloved hand to avoid damage and listen for rattles. Chase then down and fix each one.

Once you exhaust that, get a mechanics stethoscope and listen to the running engine for internal noise.

Good luck and I hope it is something simple (and cheap!)

Cheers,

Jordan

[seabeelt]

Also check the timing belt cover attachment, the piece that also has the timing pointers on it. Mine broke in half and rattled like a New Years rattle can tip I fixed it.
R/

[silvadw]

so, the simple answer is a loose stud nut on the exhaust side. Strange it suddenly came undone



The arrow shows the culprit.
but now i have a leak between the exhaust manifold and the "2" collector. The studs are not in good shape so reluctant to try to undo and re-tighten. I guess this is the source of the rough idle.

Any suggestions on the exhaust manifold/collector? the exhaust is a 4-2-1 system. I guess i should get some replacement studs and nuts

[AriK]

It's a better case scenario than your alternative 4. Still of concern but i'm glad to see it less serious.

[silvadw]

PRIZE WINNER.....
neatest first closest correct entry goes to burgandy 81.
i will be in Atlanta next week, chicago the week after, then LA and maybe SF.
Your fabulous prize is beer (one). do you live anywhere near any of those cities?

[silvadw]

oops....spoke too soon....took a drive and sound is back.....
will take off valve covers later when engine cools
Engine runs rough now, like on three pots only...

[silvadw]

like BCbrad, (viewtopic.php?f=5&t=30855#p241036) my problem ended up being broken head gasket between 3 & 4.
seems this is a common issue.