What does "thrown rod" really mean?? - Chevelle Tech

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post #1 of 15 (permalink) Old Jun 19th, 05, 12:41 AM Thread Starter
BC
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What does "thrown rod" really mean??

And what can it do to your engine??

I'm looking at buying a pretty cheap 4x4, but the lady selling it thinks it might have a thrown rod... so what does that really mean?

She says it will start and run and I can drive it around the parking lot, but will that just break it more or what??

I always kinda figured a thrown rod meant the rod came apart or something and now the engine wouldn't run at all...

Also, how do you actually "throw a rod"... is it caused by over-revving or something??

If I go and start it, what should I hear to indicate that it is in fact a thrown rod, or are there other things that could be wrong that sound/feel like a thrown rod??

Thanks,
Bill C.

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post #2 of 15 (permalink) Old Jun 19th, 05, 9:39 AM
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Re: What does "thrown rod" really mean??

The engine will make a loud knocking noise because the bearing attaching the rod to the crank is damaged and has excessive clearance. depending on how damaged it is you could save the crank and rod . I would not reccomend actually driving the truck, but I would start it to take a listen.

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post #3 of 15 (permalink) Old Jun 19th, 05, 12:05 PM
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Re: What does "thrown rod" really mean??

Thrown Rod means exacly what it says. The rod exits the side of the block. Some people call a rod knock a thrown but that isn't correct. Either way the engine isn't happy but a rod knock is much better than one sticking out the side of the block.
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post #4 of 15 (permalink) Old Jun 19th, 05, 12:18 PM
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Re: What does "thrown rod" really mean??

Either way, I would make an offer on the vehicle that reflects the fact that you will probably going to have to put an engine in it.

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post #5 of 15 (permalink) Old Jun 19th, 05, 12:26 PM
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Re: What does "thrown rod" really mean??

I threw a rod in a 231 V-6 in a 79 Buick LeSabre. It made a large, gaping hole in the side of the block in which rod was hanging out of it. Funny thing was, it started right back up . Good times, good times

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post #6 of 15 (permalink) Old Jun 19th, 05, 5:11 PM
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Thumbs up Re: What does "thrown rod" really mean??

Years and years ago, my B-I-L's little brother just under him threw a rod in a '56, 265 motor! He stopped and looked under the car and saw the hole, cranked her up AND then drove it home 6 or 8 miles running 65 to 70!!

Our old motors are tough little buggers!!!

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post #7 of 15 (permalink) Old Jun 19th, 05, 8:53 PM
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Re: What does "thrown rod" really mean??

Thats crazy running it with a rid through the pan. I guess it was already in pieces wtf is a little more damage

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post #8 of 15 (permalink) Old Jun 19th, 05, 9:02 PM
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Re: What does "thrown rod" really mean??

What does "thrown rod" really mean??


heres a example.
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post #9 of 15 (permalink) Old Jun 19th, 05, 9:43 PM Thread Starter
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Re: What does "thrown rod" really mean??

Dang Turbo... that's nasty looking!!

SO my suspicions were probably correct in that it is probably just a rod knock rather than a thrown rod.

So Bill, can you rebuild a motor that has a rod knock? what kind of damage does it do? If I make an offer, I kinda need to know if I can rebuild the motor or just have to replace the whole thing. I can rebuild it a lot cheaper than replacing it...

Thanks all,
Bill C.

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post #10 of 15 (permalink) Old Jun 20th, 05, 12:11 AM
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Re: What does "thrown rod" really mean??

You can rebuild ANY engine that has thrown a rod. Depending on the damage, you MAY have to only replace some pieces and turn the crank. OR, you may have to replace the crank, block and a head. Rebuilding an engine consists of machine work and replacing worn parts. In some cases, the block is worn (or broken) to an extent that it also needs to be replaced. Sometimes, everything except the valve cover bolts have to be replaced. But, you could rebuild the engine by retaining only the valve cover bolts!

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post #11 of 15 (permalink) Old Jun 20th, 05, 7:30 AM
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Re: What does "thrown rod" really mean??

Here is another fine example.



Since then, I've learned to never run around with a rod knocking if you want the block. Luckily the one above was just the stocker 305.

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post #12 of 15 (permalink) Old Jun 20th, 05, 11:59 AM Thread Starter
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Re: What does "thrown rod" really mean??

So if it is just a rod knocking, is there anything I can do to help it out so I could drive it 10 or so miles home? Any "tricks" you guys know of? Once I get it home, I can work on it, but not in an apt complex parking lot on the wrong side of town!!

Thanks again,
Bill C.

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post #13 of 15 (permalink) Old Jun 20th, 05, 2:13 PM
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Re: What does "thrown rod" really mean??

Quote:
Originally Posted by BC
So if it is just a rod knocking, is there anything I can do to help it out so I could drive it 10 or so miles home? Any "tricks" you guys know of? Once I get it home, I can work on it, but not in an apt complex parking lot on the wrong side of town!!

Thanks again,
Bill C.
I guess it depends on how much you want to risk throwing a rod/ruining the block/crank and/or possibly getting stranded...

Like some others mentioned, I have seen (and driven) some cars with "thrown" rods, but often they will not go far...

I have know some friends with minor rod knocks that filled the crankcase with gear oil (80-90W), and the thicker oil seemed to suppress the knock slightly (but not entirely)...Probably didn't really help...

I would say, if the knock isn't too bad, and you don't mind the risk, just drive home really slow, keep the rpms low to minimize the "knocking"/pounding, and hopefully keep things from breaking... And hope you have roadside assistance in case you need a tow...

My current 396 suffered a thrown rod... Luckily, it only took out the cylinder, and a new sleeve fixed the problem.

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post #14 of 15 (permalink) Old Jun 20th, 05, 6:13 PM
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Re: What does "thrown rod" really mean??

If you can't find a hole in the bottom end then I'd consider really lowballing her with the "needs a new engine" story and see how cheap you can get it. If it's still to much $$ to take the risk then try to start it to "see if it's complete junk or not".

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post #15 of 15 (permalink) Old Jun 21st, 05, 9:54 AM Thread Starter
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Re: What does "thrown rod" really mean??

Ok, I was finally able to get over there last night and start the truck... It's definitely got issues!! It idles real nice and quiet, but once you step on the gas and try to go, then you hear the knocking really good. Because of that and some other oddities, I was able to get her down to $500 for the truck (actually a 79 Ford Bronco!) as is. Around here, that's a pretty good deal for a 4x4! So looks like I'll be buying it and probably just tow it home and go from there.

Once I get it home, what should I do to look for and varify that it is a rod knock and how do I go about fixing it? It there something that can be done by pulling the oil pan, or is it even worth trying? Guess I'll just not 100% sure it's a rod since I've never heard one before, so I just want to be sure that's what it is.

Thanks,
Bill C.

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