Good wheeling trip, bad ride home...

[chev-mc]

Hey guys,
I got to wheel my junk finally and had a blast in the snow. I was driving it home and heard a tick/knocking sound. Checked gauges and the temp was pegged. I got off to the side and shut her off. It boiled over so I let it sit and had to call a buddy to tow me home with his little Mazda B2300 (he burnt a lot of clutch). I topped it back off with coolant and haven't had an overheating issue since. There were no heat issues up until that point. The radiator hoses were not leaking and it ran at normal temps on the trails that night.

The trouble is that I can hear a nasty knocking sound coming from the poor 350. Its much louder when the motor is cold and sort of quiets down when it warms up a little. It is also louder when I clutch in and hit about 2,000 rpm (when the motor is not under load). Oil levels are well maintained too. One of my buddies here at work is telling me it's a wrist pin and I'm hoping he's wrong. Its just too damn cold outside to dick around with it all day long.

Anybody have any ideas as to what this could be? I'm wondering if the sound and the overheating are even related at this point... and if anyone else has had this happen to them after they overheated.
Luckily I have a spare 350 TBI kicking around in a burb I bought.


Well, sort of a useless post I guess but I'd just like to get an idea of where I should start looking and things to look out for.


Specs
78 K10, 42's 350 Qjet,465,205 124K on the motor.

 

[sweetk30]

i overheated 1 a few years ago. same tick at cold and 2500-3000 rpm range. pulled it and found #1 rod bearing just ever so slightly fanning out and making the clearence to big . and i had about 5psi less oil pressure also.

hate to say it but soulds like bottom end like mine was.

the oil gets way to hot and thins to water and the front of the engine gets the oil last and from there stuff breaks down fast.

 

[chev-mc]

Glad to see someone had the same symptoms from a similar event. Any guesses as to how many more miles she has in her. I'm a gamblin' man today. I ate a burrito from the gas station.

 

[sweetk30]

ya never know. 5 sec run time to 5 years . its gamblin.

friend drove one up from down south full loaded and camper. had severe rod bearing knock. made it all the way here and to maine. still ran when new motor was installed.

 

[Thunder]

My first thought when I read your description was Rod bearing. Similar thing hapend to a buddy of mine. Not hard to fix. We just dropped the pan and installed new rod bearings. Fairly easy job in a lifted 4x4

Dont think it is a wrist pin. They usually make noise under acceleration.
Where bearings will be more constant knocking at certain or even all rpms when they get really bad.

 

[toomany]

ya never know. 5 sec run time to 5 years . its gamblin.

friend drove one up from down south full loaded and camper. had severe rod bearing knock. made it all the way here and to maine. still ran when new motor was installed.

x2

I've had motors that started knocking and threw the rod within minutes. On the other hand, I've had some that ran just fine with the knock.

The motor that came in my 77 K20 had a real bad knock when I bought it. So my friends and I decided to take it bogging to try to blow the motor (was told it was already .060 over). That motor took everything we threw at it, and then some. We couldn't kill it. Soon I replaced the motor with a fresh one and the knocking one sat for a couple years. Fast forward a couple years...I needed a motor to drop into my 82 Z28 drag car. I didn't have the 454 done yet and I just needed something to drop in to sort out the chassis/suspension. Droped the knocking 350 in and made about 50 passes down the strip with it, along with some street time. Still didn't die, the knock was getting louder and it sounded like more rods were starting to go. When I got the 454 done, out came the knocking 350 and again it sat. About a year later a friend of mine needed a motor for his v8 S10 project...you guessed it. In went the knocking 350. He ran it for a couple months before it got to the point where it would barley run and would overheat constantly. Out it came and a fresh one went in its place. Just for kicks we pulled the pan off...5 of the rod bearings were serverly beaten flat, to the point that on 3 of the 5 both halves had become one. 2 rod bearings were missing and the other one actually didn't look too bad (considering the other 7). The mains didn't look that bad either...except for the chuncks of rod bearing ground into them. That motor always gae us a thrill, I actually hated to scrap it. I wanted to make a coffe table out of it, but the GF said no.

 

[chev-mc]

Thanks for all of the info guys

I drove it 50 miles today out of necessity and it got way worse. Sounds easy enough though. I'll give it a whirl.

Thanks again,

Matt

 

[Hogback Fabrication]

You can tell from previous replies, but Chevy small blocks are some seriously tough motors.

As mentioned before, its much more likely a rod bearing than it is a wrist pin.

Once you hear a knock, I wouldn't run it but its up to you. A knock means its on its way out, whether it's 10 miles or 1000.

 

[StevoandaRedK5]

The 20-year-old 350 in my truck died (threw one rod, bent another) about 25 miles after it started knocking...must've been that run at the drag strip before the new engine went in. SBC's are indeed some tough motors though.

 

[73redblaze]

i want to see the picture of a little mazda towing your k5. no advise, that is all.

 

[86-1ton]

that's the same probelm i ran into about 2 weeks ago... i overheated the hell out of my 350 right after i blew a radiator hose... i had to go get my son, so i pushed it the 2 extra blocks there... stopped, patched the hose, tossed water in and it was knocking so bad, i thought the rod was going to come out of the block... i parked it, called for help, and went back about 4 hours later after class... i dumped some water and windshield washer fluid into it (hey, it doesn't freeze and was cheaper...!) and drove it 30 miles to my brother's house... we did an oil change, thermostat and new hoses and haven't had a problem since... it's a GM reman'd motor, i don't know when it went in... i don't have any noises in it now, but i'm still going to pick up a motor to go through and have waiting just in case...

i serously thought i blew that 350 up... i was beating myself up for it... you don't know how glad i was when it fired up and ran like there wasn't a problem in the world...