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Thrown Rod? Damn.

5K views 23 replies 13 participants last post by  68RCodeConv 
#1 ·
Ran smoother than ever yesterday, although it seemed to be a little short on power, but it's a very temper mental engine, so i didn't think much of it.

Today I had to start it 8 times before i could get it to pull out of the driveway. It just wouldn't stay running, no matter how much gas I gave it, although I wasn't purposely trying to rev it cold.

It has very, very little power driving down the road, runs EXTREMELY rough, it has a loud, deep thud sound on every engine rotation. with revving, the thudding sound gets faster, but doesn't seem to dissipate as other problems I've had in the past.

My oil's a few months old, clean as a whistle, and dead-on full, and my car has never even gotten hot.

Called my uncle and described it to him as best I could, and held the phone up to the engine. He thinks it's a thrown rod, he's going to try and come out asap and take a look at it with me.

It's had a lifter noise since I bought it, but I've been watching the oil like a hawk, and just replaced my busted temp gauge with an NOS one i had sitting in the box, but even the old gauge showed me it wasn't overheating. How could a rod be thrown under good care?

Any ideas what else it might be? I suspect I have an exhaust leak at the doughnut between the exhaust manifold and the exhaust pipes, but I don't think that would cause such problems as this one.

Thanks for your help, and I hope to god it isn't a rod. The engine was rebuilt by PO only a few years back, although I suppose that if i have to rebuild it myself, I'll learn a few things and i'll know it's done right in the end.

Any input?

Thanks
-Matt
 
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#3 ·
Sounds more like a spun bearing rather than a rod "being thrown". Oil would still look good even with the bearing problem. Usually will happen on a cold start-up. Ask me how I know. Don't know that a compression test is going to show anything either. If the sound is down low in the engine, (possibly listen with a stethescope or even a long screwdriver placed against your ear) you can bet it's not good. A lifter will sound more like a ticking noise. Internal lower end problems will have a deeper thud or clang. Good luck but it doesn't sound good. Tony
 
#4 ·
There's no mistakeing a spun main bearing!From your description.Ouch! that SUCKS!!! :thumbsdown:
 
#6 ·
If it is indeed a spun bearing running the engine is asking for disaster..The rod will eventually depart and likely destroy the rest of the engine...I would pop off the pan and take a look but I imagine the crank journal is already damaged enough that you can't just stick a new bearing in it to fix it.
 
#8 ·
Drop the pan and check the rod bolts (torque). Had the same thing happen to me this past fall, checked and sure enough one nut had backed off. Retorqued everything to spec and all it cost was a few hours time and an oil change. Don't drive the car until you diagnose the problem!
 
#10 ·
Acooljt said:
When people say a "thrown rod", what do the mean by this as it could have a few different meanings.
In my book, it means enjoying the view of the crankshaft through a hole in the side of the block/oil pan :D

OP, there should be a marked change in hot oil pressure with a bad rod bearing.

Also, an oil analysis should reveal an excess of metal (bearing materials) in the oil.

QD method is to drop the pan and look at everything.

BTW, rod bearing problems are pretty easy to tell. If you loosen a rocker arm, you'll hear a ticking noise, but it's be at 1/2 crank speed. A rod noise will be at crank speed. Once you've heard both, you'll immediately know which is which, and this applies to exhaust leaks (which appear at 1/2 crank speed too).

A little bit trickier is piston slap from excessive clearance or a collapsed skirt. The clearance usually is heard at cold start and improves, whereas the collapsed skirt makes noise all the time. It's a duller noise than a rod noise.

A mechanic's stethoscope can pinpoint the noise, as long as you know what you're hearing...

Pat
 
#14 ·
Never thought there was any question about a thrown rod! It means the rod has
separated (thrown) from the crank! Often it results in a sizeable hole in the
lower block!
 
#16 ·
The points slipped...

Damnit, that's like the 10th time since I bought the car 7 months ago. It makes a different noise every time...

Thanks for the help. I still have that ticking noise that i've had since I bought the car, I believe it's lifter noise. I'd like to repair it, but i don't have the know-how nor the time at the moment, it's finals week. Maybe someday i'll get my uncle to help me, he knows all this stuff.

Thanks again
-Matt
 
#17 ·
Lifters are a breeze to change, wouldn't worry about it.

Also, if you're tired of those points, go with an Ignitor. $80 and you've got a solid state ignition, you never have to worry about fiddling with those points every again.
 
#19 ·
I agree with Aaron. Get rid of the points and go with an electronic ignition. You will be much happier and no more messing with the points.
 
#21 ·
Well, that really is what it sounded like. I've got a few other engine/exhaust issues as mentioned, and those may have contributed to the low thud sound.

I swear, they keep slipping, and it sounds different every time. My uncle says I'm missing a star washer on the hold-down screw. Makes since to me, that would sure grip the plate better.

I would love to opt for an HEI distributor/coil, but i've got to tackle one thing at a time.

Thanks for the help
-Matt
 
#22 ·
First Aaron your not always wrong. Sometimes you have good ideas. Remember I said sometimes.

And Matt you don't have to replace the whole distributor to get electronic ignition. They make kits that replace the points in your current distributor. Most work really good for around $70. Sure beats the hell out of points.
 
#23 ·
Matt; I completely agree with what's been said about your distributor, however, your points should not be slipping, if things are correct. So, while your waiting for your electronic conversion, you may want to look that disty over! Check the overall condition of it. ie; threads in plate, shaft play, etc. Make sure that your screws, and washers are correct for the application. As far as your engine noise goes, anything from here, would be just a guess. I hope it's nothing major. Like other's have posted, it could be a lot of things, maybe something trivial. How's your oil pressure? Was the car running smooth, when it kept stalling? Do you have a magnetic plug in your oil pan? You've been saying you've had a lot of lifter noise. Could this be a cam knock? or Something in the valve train? Probably not, but...............at this point, it really could be anything.

Best Regards, J.R.
 
#24 ·
Put a Pertronix in it. End of problem.

I had a timing chain jump a tooth once and it behaved exactly like you describe. Engine would run but it made all kind of funky noises.
 
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