burnt valve?
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From: Imboden/Little Rock AR
burnt valve?
I have recently done some work on a 302 that i have in a 72 ford truck. I pulled it and tried to stop some oil leaks. when I had it out I tightened up the rockers (to stock specs) because I had noticed I had a rattle on the right bank before, I checked them to make sure they still worked too. I put the enging back in and it ran fine for a while but now i have a clank on the right side again. Also at around 2500 or so rpm it sounds like it's missing on one cylinder and the enging surges a little bit. My dad tells me that tightening up the rockers did this, and its could have burnt a valve. I think he's full of it. Could tightening up the rockers cause this, and if not what could be causing it?
Thank you,
Brad Bridges
Thank you,
Brad Bridges
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From: midwest
usually a valve thats burned misses worse on idle and once you rev the motor it smoothes out. you may have a bent pushrod, make sure your valves arent adjustable, some early ones were. that could be your problem if they are and you didnt adjust them correctly.
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From: Imboden/Little Rock AR
I don't think the valves are adjustable, but i'm not sure. the engine is around a 72. Could you see enough of the pushrod to tell if it's bent by removing the valve covers?
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if the pushrod is bent you can see it when it turns while the engine is running. If the rockers are nonadj. you wouldn't have been able to tighten it. if it is adj. too tight it will hold the valve open slightly and burn it. If it's really to tight it will cause a interference with the valve keeper and bend the pushrod as the valve can nly open so far before the compressed spring prevents further opening and at that point something else has too give.
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From: Imboden/Little Rock AR
i'm not sure if the rockers are adjustable, i just tightened the rocker mount nuts. I tightened them to stock specs and checked them. Can you run an engine with the valve covers off and not get oil everywhere, i've never tried it before
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From: Imboden/Little Rock AR
if i have a bent pushrod should i just replace it, or should i loosen the rocker some?
Does anybody know what the torque specs are supposed to be on the rockers?
Does anybody know what the torque specs are supposed to be on the rockers?
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From: washington!
mmm, well you have to replace the pushrod if its bent, you cannot bend it back and it will not retake its previous shape, loosening a rocker at this point would not help any.
Second up, I don't know the specs on the non-adjustable rail rockers, I just wrench them down by hand myself and have not had a problem (but I have a very good feel for torque). As for the adjustable type, threre is a procedure to adjusting those, however I can't recall all the steps as I haven't messed with a rocker adjustment in 5 years. A shop manual should have it in there, but what it boils down to is setting all the rockers to a certain clearance between the rocker tip and the valve while the engine is cold (usually with a feeler guage). This is followed by starting the engine letting it warm up and then loosening the rockers till they make noise and then locking the nut down a certain amount of turns to preload the lifters. its a mildly messy procedure but there are oil deflectors available from most parts places. Anyhew hope this helps some.
Second up, I don't know the specs on the non-adjustable rail rockers, I just wrench them down by hand myself and have not had a problem (but I have a very good feel for torque). As for the adjustable type, threre is a procedure to adjusting those, however I can't recall all the steps as I haven't messed with a rocker adjustment in 5 years. A shop manual should have it in there, but what it boils down to is setting all the rockers to a certain clearance between the rocker tip and the valve while the engine is cold (usually with a feeler guage). This is followed by starting the engine letting it warm up and then loosening the rockers till they make noise and then locking the nut down a certain amount of turns to preload the lifters. its a mildly messy procedure but there are oil deflectors available from most parts places. Anyhew hope this helps some.
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if the rockers had nuts they are adjustable whereas if they had bolts they aren'tand you tighten them to about25lbs torque. If you adjust the rockers whiole the engine is running and if it has decent oil pressure you get oil everywhere, try putting a loose rag over them and only uncover the one you're working on , if you have the deflectors use them. Loosen them until they clatter noticably and then tighten until they just stop making noise and then 1/3 to 1/2 turn more, this should cause your engine to run rough and stumble briefly but it will smooth out then go on to the next one , also set the idle as slow as possible to minimize the oil bath.
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From: Imboden/Little Rock AR
I checked the rockers and pushrods yesterday and none of the pusrods were bent. I did find that one of the ball joints on the rocker wasn't setting down on the stud good so the rocker had to have been clanking a little. When i took of the nuts and removed the rocker I noticed that one of the nuts was cracked which could have caused it to loosen up. Also, I have a shop manual for 1973 and up trucks(even though mines a 72, that's all i could find) and it says to just torque down the stud nuts to 17-23 foot pounds. I hope that fixing the broken nut will fix the clank.
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