Broken Push Rod
Thread Starter
Safety Car
Joined: Nov 2000
Posts: 4,419
Likes: 6
From: Arroyo Grande CA
Broken Push Rod
Just cruising down the freeway the other day at 70mph. When I exited, I heard a tapping noise, sounding like a loose tappet. Took it to the shop to be diagnosed and they found a broken #8 intake push rod. No other damage could be found. Engine has 117k on it. Valve train was extremely clean, thanks to Pennzoil Platinum 
. Oil is still clear enough to easily see the hash marks on the dipstick and has 8k on it with 20% on the OLM. Oil pressure is OK.
The push rod was broken almost exactly in the middle. This engine hasn’t been pushed hard since around 20k. This is a first for me and my mechanic. He checked with Chevy for any issues like this and they didn’t know of any. Everything is back together and purring.
I was just curious if anyone else has had an issue like this.
. Oil is still clear enough to easily see the hash marks on the dipstick and has 8k on it with 20% on the OLM. Oil pressure is OK.The push rod was broken almost exactly in the middle. This engine hasn’t been pushed hard since around 20k. This is a first for me and my mechanic. He checked with Chevy for any issues like this and they didn’t know of any. Everything is back together and purring.
I was just curious if anyone else has had an issue like this.
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
Thats weird. Ive seen them bend but not break. Check the springs and the spring pressures. Maybe it saw coil bind of valve float at some point. Strange. Hopefully it was just one of the wierd one time deals.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Bud,,,, You have more problems than just a bent pushrod. That valve contacted the piston or the valve stuck shut because of a spring issue or rocker issue.
Recommend a compression test AND a cylinder leak down test be accomplished. That will eliminate a bent / damaged valve issue as a result of the damaged pushrod.
Are you sure you dont have a broken/damaged valve spring??
Bill
Recommend a compression test AND a cylinder leak down test be accomplished. That will eliminate a bent / damaged valve issue as a result of the damaged pushrod.
Are you sure you dont have a broken/damaged valve spring??
Bill
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Thread Starter
Safety Car
Joined: Nov 2000
Posts: 4,419
Likes: 6
From: Arroyo Grande CA
Bill, a comp/leakdown test was not done. Which I will get done. 
No broken valve spring(s). The engine is purring perfectly it seems, no issues.
The bending of the rod, as we thought, may have come after the break, by the 2 halves pounding on each other. The car was driven approximately 20 miles, rpm's kept under 1500, after I noticed the ticking noise. In piecing the halves together, the best I can, there doesn't appear to be a bend at the break point, only at the mid-points of the 2 pieces.
Don
No broken valve spring(s). The engine is purring perfectly it seems, no issues.The bending of the rod, as we thought, may have come after the break, by the 2 halves pounding on each other. The car was driven approximately 20 miles, rpm's kept under 1500, after I noticed the ticking noise. In piecing the halves together, the best I can, there doesn't appear to be a bend at the break point, only at the mid-points of the 2 pieces.
Don
Race Director
Joined: Jan 2008
Posts: 16,028
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From: oregon
you miss a shift at high rpm somewhere in the past? just was thinking about that and wondering if you fatigued the metal and then it finally went.
i was skimming a book on performance LS builds last night and noticed they mentioned over revs and missed shifts as the #1 cause of bent or broken pushrods in the stock LS engines
i was skimming a book on performance LS builds last night and noticed they mentioned over revs and missed shifts as the #1 cause of bent or broken pushrods in the stock LS engines
Thread Starter
Safety Car
Joined: Nov 2000
Posts: 4,419
Likes: 6
From: Arroyo Grande CA
^^^^^^^^
Yes, over-revved it one time on a missed shift. I remember it because it scared the crap outta me. Very quick to lift and very relieved when everything seemed normal after the fact. That had to have been close to 100k miles ago. Very well might have fatigued it at that time and it just now failed.
Yes, over-revved it one time on a missed shift. I remember it because it scared the crap outta me. Very quick to lift and very relieved when everything seemed normal after the fact. That had to have been close to 100k miles ago. Very well might have fatigued it at that time and it just now failed.
