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Old 02-24-2011, 11:04 PM
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327 rocker slipped off the spring

I have a new rebuild on a 327 .40 over with cast iron heads and hydraulic lifters. Motor doesn't have 100 miles even on it yet, I was running it one day and shut it off about a 1/2 mile from my house. I started the engine a few minutes later and heard the ticking, stuck lifter on the drivers side. I had no choice but to drive it home slowly, pulled the valve cover and #3 cylinder rocker slipped off the spring, funny thing was it happened after the chevelle was off. No sign of ticking before while running like there was a rocker loose or anything. Of course the push rod got bent slightly, and I don't think the cam was affected. I did run the chevelle 3/4 throttle for about a quarter mile a couple times and she ran great. I did not mess with the rockers since I got the block and heads back from the machine shop. They bored and decked to square and everything balanced. My question is should I have been the one to check all the rockers after coming back from the machine shop? I assumed it was all good and all I had to do is dress it up. It just might have been a fluke thing I guess. Should I go back and check all the rockers after i get the machine shop to replace a new push rod? If so I will have to do it while the 327 is running, since it will be difficult to turn the engine over properly while engine is off for each cylinder stroke. Does anyone have any advice on my situation or is it a simple as I suggested. And probably just a fluke occurence? Thanks in advance, Michael

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Last edited by chevyrally68; 02-24-2011 at 11:05 PM. Reason: wrong title
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Old 02-25-2011, 01:13 AM
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I get from what you're saying is that the machine shop built the engine and supposedly adjusted the valves.....then you installed it and fired it for the first time? If that's the case did you use a good break in oil or additive like ZDDP+ and did you break the cam in at 2000-2500 rpm for about 25 minutes? If you didn't you probably wiped a cam lobe which could cause those symptoms.......not good. DON'T run the engine until you verify exactly what happened......and good luck.
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Old 02-25-2011, 05:44 AM
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Quote:
Originally Posted by 327NUT
I get from what you're saying is that the machine shop built the engine and supposedly adjusted the valves.....then you installed it and fired it for the first time? If that's the case did you use a good break in oil or additive like ZDDP+ and did you break the cam in at 2000-2500 rpm for about 25 minutes? If you didn't you probably wiped a cam lobe which could cause those symptoms.......not good. DON'T run the engine until you verify exactly what happened......and good luck.
couldnt have said it better myself.. i would like to think a decent machine shop would have given you direction on the do's and the do's nots of a flat tappet cam break in. these days with all the flat tappet failures, i will never build another engine without a roller tappet/cam unless i'm also doing the break in.. good luck
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Old 02-25-2011, 10:35 AM
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Yes motor was broken in properly with break in additive and runned for 25 minutes between 1500-2000rpms and is running great. Just had this rocker slip for some reason? I have driven it several times after the break and making adjustments to the carburetor with no problems prior with the rockers. Still have very low miles on the car itself since the break in.
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Old 02-25-2011, 10:37 AM
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Quote:
Originally Posted by chevyrally68
Yes motor was broken in properly with break in additive and runned for 25 minutes between 1500-2000rpms and is running great. Just had this rocker slip for some reason? I have driven it several times after the break and making adjustments to the carburetor with no problems prior with the rockers. Still have very low miles on the car itself since the break in.
well check the stud to make sure it hasnt work'd its way out.. the rocker doesnt just come off, something is wrong...
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Old 02-25-2011, 10:52 AM
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rocker was still attached it just slipped off to the side of the spring so it was still attached, but could not function properly and it was on the exhaust side of the valve. stud is fine and nut was still in place not completely off that why it is so strange. I guess it the rocker got loose and during the exhaust stroke it slipped off to the side.
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Old 02-25-2011, 11:13 AM
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i'm confused i understood that everything is perfect but the rocker just came off and the pushrod bent, those circumstances dont just happen to take place without there being an underlining issue..you keep saying slipped off the side of the spring do you mean valve tip? take a close up picture of the valve tip and post it in this thread if you can please
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Old 02-25-2011, 11:23 AM
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I whole heartedly agree, if the rocker arm was adjusted properly and you had lets say 120 lbs. on the seat spring press. there is no way it can just "slip off"......something is amiss.
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Old 02-25-2011, 11:23 AM
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Bent pushrod

I would check to see why the pushrod bent. Valve spring bind, valve train geometry, valves adjusted too tight ?
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Old 02-25-2011, 12:11 PM
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Rocker tip sitting off to the left of the spring after slipping off the center of the spring. Push rod still moving up and down as normal operation while i crawled home to the garage bent the push rod.
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Old 02-25-2011, 12:28 PM
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sorry i don't have a picture to send so you guys can see, i guess it is confusing when trying to explain, I will try again, yes the rocker tip slipped off the spring and the tip of the valve(center of the spring,exhaust side). I turned the engine off the and about 5 minutes later fired her again and the rocker was ticking. I had no tools and fairly close to home so I drove her very slowly home that bend the push rod driving her home.
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Old 02-25-2011, 12:36 PM
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It is far more likely the pushrod bent first. Rocker arms do not just slip off the valve stem unless something is wrong.

Check the pushrod slot in the head(or the guideplate if so equipped), the stud for pulling from the head, rocker adjustment nut vibrating looser(different height on the stud than the others), burnt rocker ball, burnt rocker ball socket in the rocker, mangled pushrod cup in the rocker.
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Old 02-25-2011, 01:34 PM
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Quote:
Originally Posted by ericnova72
It is far more likely the pushrod bent first. Rocker arms do not just slip off the valve stem unless something is wrong.

Check the pushrod slot in the head(or the guideplate if so equipped), the stud for pulling from the head, rocker adjustment nut vibrating looser(different height on the stud than the others), burnt rocker ball, burnt rocker ball socket in the rocker, mangled pushrod cup in the rocker.
X2 I Agree with this.


Cole
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Old 02-25-2011, 02:41 PM
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Yes that seems to make more sense, push rod bent causing the rocker to slip, I will double check the items you listed. Something happened causing the push rod to bend, something got sticky in there. My Dad seems to think is was a valve guide. Just hope nothing to damaging I just put this engine all back together, would hate to have to pull a head or engine again. Like I said drove it 3/4 throttle a few time before this incident happened. I was checking the #.35 squirter I changed to see if helped the slight hesitation I had. And it did, so I thought it was going to be a good day till this
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Old 02-26-2011, 04:20 PM
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Rocker issue

I agree, something caused this to happen. I also would take the valve locks, retainer and spring off the valve to see if the the valve seized in the guide. This would account for the bent pushrod. although this is not a common problem in SBC's, it does happen. I would also check the rocker arm stud. When changing cams and valve spring pressures, frequently the stock SBC rocker arm studs start to pull out resulting in excess valve lash causing a failure where the threaded portion of the stud breaks or high cam lobe wear resulting in a flattened lobe.
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