bending pushrods
Freshman User
Joined: Mar 2007
Posts: 34
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From: Jacksonville
I have a simular problem, last week I was heading back to work after lunch when my 351c started clicking like it was low on oil. My oil press. was steady at 50psi so I just took it easy to the nearest store where I checked the oil which was a little less than half a quart low. added oil but still the same noise. After work I noticed that I was getting a small backfire through the carb at idle. I drove it home taking it real easy and started working on it today. What I found puzzles me. The clicking sound was coming from the passanger side of the engine so I pulled the valve cover on that side and found that the #1 cylinder intake valve pushrod was bent and the exghuast valve pushrod was broken. The valve train is all stoke save for a cam with longer duration lobes so the engine can breath better. I replaced the affected pushrods and now the engine runs fine again. Any idea what might cuase this?
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5th Wheeling
Joined: May 2006
Posts: 30
Likes: 0
No, still having issues. Went fine for a couple of weeks, I'm sure there is another one bent. Incidently the first time one of my pushrods was completely broke in half also. After this I have a factory spec replacement cam to put in- less lift than the "lopey" one I swaped out when I had issues with the torque cam. No sign of any issues with anything. Only thing I can figure is overrevving when the oil is thick, judging by the first time the pushrod was broke in half- it had obviously got in a bind as there was a groove where it had caught the head where it goes through. Other consideration might be the valve springs are getting weak for high revs. I've ran a compression test after replacing pushrods and all is well so no bent valves. ?????
Freshman User
Joined: Mar 2007
Posts: 34
Likes: 0
From: Jacksonville
Hm, I never get my rpm's above 4k, but the pushrod that broke on mine shows no sign of hitting anything that could have cuased the break. The cam I have also has a little lope to it but I have had it in the engine for almost 9 years with not even one problem so I am a little curious if anyone might have a clue as to what might cuase this.
Lead Driver
Joined: Mar 2004
Posts: 8,924
Likes: 153
I'd take then springs off the valves and see if the valve guides are worn out. Check piston to valve clearance. Check retainer to top of valve guide clearance. Make sure the rocker fulcrum isn't running out of clearance in the rocker arm. Check push rod length.
Senior User
Joined: Nov 2005
Posts: 429
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hey fellas, the bent pushrod deal, i can only say what has happened to me. a collapased hydro lifter for whatever reason. the pushrod leaves its socket and it goes from there. ticking is a first indication. there are ten different reasons at least which might have started the chain. my exp and just my OP. part of the fun is always figuring out why (grin) me
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5th Wheeling
Joined: May 2006
Posts: 30
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that might make sense- never heard any ticking before it happened the first time-then Wham- one looked like an S and the other broke in half, had to bind where it goes through the head. Means serious misalignment such as leaving the center. Need this truck for daily transportation though, so I'm not checking the guides and springs as earlier suggested although the springs may be weak (but they are double). Gonna swap cam and lifters on Wed for factory CJ cam. Will post results then. BTW I'm thinking of advancing the cam 4 degrees, anyone know how much this will change my power range? and the timing chain is not in question.
Senior User
Joined: Nov 2005
Posts: 429
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hi space paul, first and foremost i for one am STONE ints in what YOU find and WHAT you do. the4dr advance. it is well known it will alter your powerband BUT there are so many variables that go with this it is imp for ME to tell you anything that i could stand by honestly. good luck GO for it. n&i are listening good or bad. its all good no matter what later us MD. let us know we are into it period. ps good point ab time chain, first things first, very good, wish we was there in your shop w u. carry on.
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5th Wheeling
Joined: May 2006
Posts: 30
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just looking for a general powerband range. factory cam peak HP at 5400. very little done to this engine as far as other mods go. aftermarket carb (holly 600 vac secondarys, light spring..but its not enough breath for higher RPMs anyway). bored .040 over (I know, dangerous for a thinwall block). Pistons yeild about a 10:1. Duraspark 2. Thats it. even has factory manifolds. Tried advancing the torque cam when I had it in. Monstorous bottom end but completely died at 4000. Factory cam has a more lift and duration but don't want it to die before 5000. I'll just leave it at factory specs if thats the case. I think the springs must just be getting to weak to support higher RPMs now. Its a 1970 block (2 bolt mains) and even though I push it sometimes and the bottom end is tight it still sounds "loose" above 5500 compared to the 4 bolt main clevelands I've had. I'm also on a fairly tight budget so don't want to tear into it many more times just to change the cam timing.
Senior User
Joined: Nov 2005
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hi space, paul, great post , 1st i THINK,my op, for now str up on on cam, yr on it. hey dura spk is not punk when right. old wives tale. i hear you on $. i am a workin boy. springs are always an issue. 40 over, that says to us you get it (GRIN) depends on torque plate and who.hey space,you dont sound like a FRESHman to me boss(GRIN). i hear you on cfm and light spring also. velocity always a critical issue my yng buck has done the math, 550 to 650 every time. we run 600cfm wth v sec rbr. my op only. paul.
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5th Wheeling
Joined: May 2006
Posts: 30
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thanx F/S. been doin thish stuff 4 yrs. Got out of twisten wrenches and decided 2 just sell the parts now. (actually 10 yrs now). Had plenty of $ in my youth, but I'm trying to keep a family going now. Putting the factory cam in Wed. Will post on after effects. Still planning to run it hard, but decided to go ahead and advance it 4 degrees. Has an AOD behind it so I think it is the best choice. I had a Mach 1 back in the day and it turned 2500 with factory 3.25 gears at 55mph., so I think the advance will work good with the AOD considering its a daily driver. Thanks again for the support.
Senior User
Joined: Nov 2005
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hi sp, we will wait for update, you sound like a polite man but remember, do not thank n&i for support, we are all in this together. we respond because we like the way you speak and we are into it. this is intended to be a compliment. you know what i have learned in life. FAMILY is everything, without that, the baddest block on the street means nothing. we RESPESCT you for this always. later US. paul. md.