Bent push rods = sticking valves...again?
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Laughing Gas
Joined: Jan 2003
Posts: 1,082
Likes: 40
From: Melbourne, FL
Bent push rods = sticking valves...again?
I had a 78 Bronco with a 400. It was a project that did a lot of sitting around. When I tried to get it runnin, it started to steadily run worse, losing power. I dug into it to find 5 or 6 bent intake push rods. The valve guides were seriously gummed up and causing the valves to stick, so I pulled the heads and had the guides reamed. It ran ok and I parked it again.
Fast forward a couple years. Now my brother-in-law has the truck and the same thing has happened again. Went to get it running and it steadily ran worse and worse. He figured it was the carb so he decided to replace the intake and carb. When he pulled the intake, he found this...another 5 bent intake push rods. What is going on here?! I told him he needs to get the heads rebuilt.
Has anyone else ever had a problem like this? Anybody think there is a bigger problem here, or should rebuilt heads fix this one?
Fast forward a couple years. Now my brother-in-law has the truck and the same thing has happened again. Went to get it running and it steadily ran worse and worse. He figured it was the carb so he decided to replace the intake and carb. When he pulled the intake, he found this...another 5 bent intake push rods. What is going on here?! I told him he needs to get the heads rebuilt.
Has anyone else ever had a problem like this? Anybody think there is a bigger problem here, or should rebuilt heads fix this one?
Last edited by broncoholic; Mar 20, 2005 at 05:32 PM.
Senior User
Joined: Sep 2004
Posts: 263
Likes: 0
From: FLOWER MOUND,TX
wow...i wonder if the timing chain jumped a gear or two...seams like that would have things opening and closing-comming and going at the wrong time...the thing i see with this pic is that it is happening on both sides...what would be the chance of both heads giving out at one time so that leads me to believe it is what is controlling the pushrod,lifter,valve movement...camshaft...what controlls the camshaft???..timing chain and gears..
bring no1 piston to top dead center (left front passenger) and see where your timing mark is...
keep us posted...
bring no1 piston to top dead center (left front passenger) and see where your timing mark is...
keep us posted...
Senior User
Joined: Sep 2004
Posts: 263
Likes: 0
From: FLOWER MOUND,TX
one other thing i thought of...sounds like it is sitting for a while before you guys are starting it...maybe hydraulic lifters have blead down allowing too much play for the pushrods...and the pushrods fall out of the rocker arms...did you prime the oil pump before starting from sitting a long time?
just a thought ,i'm not a mechanic
just a thought ,i'm not a mechanic
Thread Starter
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Laughing Gas
Joined: Jan 2003
Posts: 1,082
Likes: 40
From: Melbourne, FL
Definitely no priming of the oil. Too high tech for this shade-tree mechanic.
When I originally bought the truck, I recall the guy saying the motor was rebuilt and it had an RV cam in it. Actually, he said the guy he bought it from had the motor rebuilt. A lot of word-of-mouth here. I put stock size replacement push rods in it the first time. Would an RV type cam use stock length rods? How can we check what size rods are needed? Anyone know if there should be an i.d. on the camshaft, possibly at the timing gear? This would obviously help inidentifying rod length.
Thanks
When I originally bought the truck, I recall the guy saying the motor was rebuilt and it had an RV cam in it. Actually, he said the guy he bought it from had the motor rebuilt. A lot of word-of-mouth here. I put stock size replacement push rods in it the first time. Would an RV type cam use stock length rods? How can we check what size rods are needed? Anyone know if there should be an i.d. on the camshaft, possibly at the timing gear? This would obviously help inidentifying rod length.
Thanks
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