Not A Spun rod bearing

[John S.]

The car is a 33k mile Duntov car when I purchased it 5 years ago. My first Corvette actually. I now have 44k miles on it. I drove it down to Pomona today to see good friends Charlie Bacon and Jim Gessner. On the way home I took the engine up to 5,200 rpm and experienced slight vibration while getting on the freeway. Shifted and it went away. Drove the car 65 miles home with no issues. Exited freeway. Took it back up to 5,000 rpm and it was still there. Now I am thinking what could it be. I have been playing with the fan clutch and the proper amount of viscous fluid for it to start to hook up at the right temp. When I pulled in the driveway I popped the hood to observe the fan and pullies at the higher rpm. Took it up to 5,000 one more time and vibration got much worse. Backed off and the blipped the throttle a time or two. Vibration and knocking now. I have had this happen one other time on a small block. It turned out to be a spun #8 rod bearing. Any ideas?

Car is now sitting outside with me inside pouting!

[Carl N.]

Re: Spun rod bearing

check the simple things first - take all your belts off and see if it goes away - could be a broken motor mount or broken loose transmission tail shat mount. check the oil - smell of it and see if you smell gasoline if the fuel pump is going away you could have pumped gas in pan thus thinning the oil - check everything you can think of and if nothing shows up pull the pan - could be harmonic balancer if it is the original and 40+ years old the rubber may be gone - others should chime in with ideas

[Gary C.]

Re: Spun rod bearing

John,

How did you feel the vibration; steering wheel, clutch pedal or ?

Gary
....

[John S.]

Re: Spun rod bearing

The vibration was in the whole car. Going to get off my butt and go check the oil. Maybe get it on the lift and drain it to inspect.

[Tracy C.]

Re: Spun rod bearing

A spun rod will typically come with sound effects..

[Don H.]

Re: Spun rod bearing

My thoughts too. If it were a bearing you would hear it. Good luck, Don H.

[Ed H.]

Re: Spun rod bearing

John, give me a call and I will come over and help. Lost a rod bearing in my 60, drag racing. The oil will smell like engine is burning. I was turning about 8,000 at the time.

[Page C.]

Re: Spun rod bearing

You have received lots of good advice. I agree with checking the easy things first. I would remove the valve covers and see if you might have pulled a rocker arm stud.
Hope it's a minor problem
Page Campbell

[James G.]

[Philip P.]

Re: Spun rod bearing

I broke a valve spring on number 4 will never forget I thought I was driving a thrashing machine.
Phil

[John S.]

Re: Spun rod bearing

Long overdue update on the 67 car. Removed the pan and checked all the rod and main bearings. No problems there. Buttoned it back up and then had Ed Hoffman come over and give me a hand. Ran a compression check on all cylinders with readings between 180-195 lbs. Checked top dead center on balancer and it was good also. Replaced all the plugs and fired her up. Ed immediately told me to shut it off and look at the fan and water pump assy. About an inch or two of travel at the fan tip. Turns out the original water pump bearing had refused to function properly without the associated ball bearings! I removed the pump and sent it out to be rebuilt.

Assembled it all back together a few weeks ago and everything is right with the world again!

I know it was suggested early on to go after the simple things first, I did not obviously do a very thorough job of that. I did give the fan blade a tug when I first got back that day but not enough I guess.

I am glad it only turned out to be the water pump and not anything more serious. Thanks to Ed Hoffman for his time knowledge in tracking down the culprit.