bending pushrods
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5th Wheeling
Joined: May 2006
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bending pushrods
I have a truck that has a 351C 4V in it. Pulled it out of a car (4 speed and put it in a truck. Had a lopey cam in the car when I bought it- can't identify it. Anyway I put a melling high torque cam in when I put it in the truck. I ran it nearly 30,000 miles and out of the blue it started bending pushrods- replaced the bent ones- and it bent more. Bending them on both heads. I swapped the othe cam back in but its a bear to drive without a stall converter. Think it might have bent another pushrod - afraid to look- still runs strong when U drop the hammer. Checked the compression before I swapped cams (thought it might have bent a valve) and its 160 on all cylinders. I swapped cams because I thought there might be a worn lobe but there wasn't. Anyone ever run into this problem before. 1970 block w/ Quench heads- think there an original match to the block but haven't checked the numbers.
Junior User
Joined: Apr 2005
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From: Whitehorse Yukon
Its not that no one wants to help. you have a strange situation on your hands, in that it went for so long before this developed. Some things that would normally come to mind are coil bind of the springs. Ive seen rotaters put on to incorrect springs. Piston to valve interference would be considered but you have changed the cam and the timing chain. Incorrect pushrod length could also be a factor. hopefully you or someone else will be able to shed some light on this. Some things are easier to diagnose hands on. GL
Postmaster
Joined: Aug 2001
Posts: 4,270
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From: Delaware
If the valve train is worn and you have too much clearance, the pushrods could fall out. They may beome bent at that time.
You would have a lot of valve noise at idle, if there was that much clearance.
Did you have any valve noise?
You would have a lot of valve noise at idle, if there was that much clearance.
Did you have any valve noise?
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5th Wheeling
Joined: May 2006
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some ticking- mild, though. thats how I discovered the first one. After that it started missing all at once is when I found more. thats why I thought it might be worn lobes on the cam. the cam I put back in measures .010 more on the lobes than the one I took out. Still has double valve springs on it. My plunger depression is measuring between .030-.040 which I thought was excessive but from what I can find its acceptable. Have got a mild ticking again but haven't pulled a cover off to check it yet- figure I might as well wait till it has a solid miss again. I have plenty of pushrods. Just can't figure out why all of a sudden this is happening after so many trouble free miles. Uses no oil and compression is 155-160 on all cylinders.
Lead Driver
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From: Albuquerque
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Postmaster
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5th Wheeling
Joined: May 2006
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stock stamped rockers, oil pressure tends to run high. should I try thinner oil? I run it hard so I have always used 20-50. By hard I mean over 4000 RPM for 10-15mi at a time w/6500 peaks- without much warm up a couple of times a week. I know thats bad but so is loosing a job. oddly enough it'll seems to bend the pushrodswhen I'm driving it easy in town. Intakes and exhausts both and random cylinders. I thought it might just be metal fatigue but bend new ones to. Maybe I should just break down and get hardened ones. Worries me that something else is going on but I can't figure it out. I'm afraid if I put hardened ones in something more serios might break.
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5th Wheeling
Joined: May 2006
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Added info- I have been mixing 2 gals of e85 in with 14 gals of gas- no noticable power loss and I get 40-60mi more from a tank of gas. First thought was that maybe it could be siezing the valves for and instant but seems unlikely or I would have had more serious problems by now. Only thing I noticed was it ate the clear sight plugs (turned em spongy) on the Holley but no other damage to it.
Posting Guru
Joined: Jan 2005
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From: The Vieux Ford, Kansas
Thats a big jump mabey you should try 10-40 or 10-30, I run 15-40 in my 400. I wouldn't go from one extreme to the other like that you may not have any oil pressure with 5-30 if you have been running 20-50
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5th Wheeling
Joined: May 2006
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naw, think it'll be OK- runs 80psi at idle full operating temp. I poked a small hole in the oil pan about 6000 mi ago- checked a main and a couple of rod bearings while I was changing the pan. Looked like new.
Freshman User
Joined: Jun 2004
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I had this problem, albeit with a 715hp Windsor race engine, but still worth checking. I was actually busting Jesel rockers in half. Come to find out my lifters were seizing in the bore. Some lifters were so bad that I could not get them out. In my case the lifter bores needed brass bushings to begin with.
If you are replacing the rods pull the lifters out and look for any scoring on the sides. If you are not getting adequate oiling to the lifters, and they are seizing at all, I could see it bending pushrods if they are the weak link.
If you are replacing the rods pull the lifters out and look for any scoring on the sides. If you are not getting adequate oiling to the lifters, and they are seizing at all, I could see it bending pushrods if they are the weak link.