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Old 05-16-2010, 10:49 PM   #1
Lanny / San Diego
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Default 312 Y-block valve lash problems

Here is my tale of woe
Three months back, I bought a '56 Ford pickup with a 312 Y-block in it.
It had a loud tappet (lifter) noise right from the get-go.
After trying numerous times to adjust the number 6 intake valve and talking to several mechanics, they suggested it might be a good time to overhaul the engine, again.
After tearing the motor down, we saw that there was no abnormal wear anywhere.
I had the engine rebuilt with a new Iskenderian cam, a valve job, resurfaced tappets, push rods were inspected for straightness, a new adjusting nut, taking, we thought, all of the necessary steps to eliminate this lifter problem.
After reinstalling the engine and fine tuning everything, I am still having the exact same problem with the exact same #6 intake valve.
We set it as it instructed to .015 and literally, without fail, in 15 miles or less, it is reading .025 or more, and the tappet noise it back.
I am seriously starting to think this truck may need an exorcism!
Has anyone else ever had any kind of problem of this nature with their Y-block?
Any ideas or suggestions concerning this most inexplicable problem would be Greatly Appreciated!
Thank you.
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Old 05-17-2010, 12:39 AM   #2
Chalupa55
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Default Re: 312 Y-block valve lash problems

Are you using the "jamb nut" style or the later style that uses a nut with an interference fit? I've had issues with the latter loosening prematurely. If your using the interference style the threads may be loosening up preventing it from staying tight. I prefer the early jamb nut style myself, others may disagree, but thats my experience.
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Old 05-17-2010, 08:00 AM   #3
Ole Don
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Default Re: 312 Y-block valve lash problems

I like the self locking style because they are faster to adjust. What you seem to have is one rocker with loose threads. Replace that rocker, or put in one adjuster with a lock nut.
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Old 05-17-2010, 05:25 PM   #4
George/Maine
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Default Re: 312 Y-block valve lash problems

I think if you change the rocker arm with another and see if problem moves to another cylinder.
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Old 05-17-2010, 10:30 PM   #5
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Default Re: 312 Y-block valve lash problems

Quote:
Originally Posted by Ole Don View Post
I like the self locking style because they are faster to adjust. What you seem to have is one rocker with loose threads. Replace that rocker, or put in one adjuster with a lock nut.
That sounds right to me, and is the easiest thing to try. It's called the KISS program.
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Old 05-18-2010, 09:28 AM   #6
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Default Re: 312 Y-block valve lash problems

Did you rebuild the rocker assemblies? a worn shaft will make the rockers hard to adjust because the rocker wont always reat in the same place. Also tip wear can be a problem. Rocker shafts are very critical in these engines and need to be looked into.
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Old 05-19-2010, 08:23 PM   #7
Retro Jim
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Default Re: 312 Y-block valve lash problems

I have to agree with the others on this one . There is a good change the adjuster nut is bad so replace with a new locking nut plus while you have the valve cover off that would also be a good time to remove the rocker assembly and examine that very well for any problems .
My guess it a bad rocker adjusting nut ! You can also add some Blue lock tight on the threads too .

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Old 06-05-2010, 11:37 AM   #8
Customline Vicky
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Default Re: 312 Y-block valve lash problems

I think they make oversized ones, but I like the ones with a jam nut too and for the ones that did that on mine I changed them and have had no more rattle ..
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Old 06-05-2010, 02:55 PM   #9
George/Maine
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Default Re: 312 Y-block valve lash problems

Something to try,slide the rocker over and check bottom of shaft see if it worn,switch rockers,if that doesn,t help.If the cam was replaced with no change,My guess your lifter,or valve is binding,is push rod hitting head or gasket.
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Old 06-05-2010, 07:28 PM   #10
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Default Re: 312 Y-block valve lash problems

I don't think this is your particular problem,but I used to have trouble with my old 292 losing adjustment on 2 or 3 rockers. It turned out to be the bolts that held the rocker assembly to the head were pulling out every time I tried to adjust it. The bolts were soft and were stripping their threads off.
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Old 06-05-2010, 08:02 PM   #11
Bill Steiner
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Default Re: 312 Y-block valve lash problems

I think it is the adj bolt or rocker arm. Not that it has any thing to do with it but I remember that the 312 adj to .019. I looked in my old manual and it said .019 hot , both intake and exhaust. Bill
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Old 06-05-2010, 08:04 PM   #12
Bill Steiner
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Default Re: 312 Y-block valve lash problems

My post above is with a stock cam. Yours is probable different. Bill
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Old 06-06-2010, 10:28 AM   #13
George/Maine
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Default Re: 312 Y-block valve lash problems

I had a problem with one lift on a 235 chevy 6 no matter what i did still have a noise.I think when cam was ground, they messed up and the start,or close,there was more clearance then the area that you would set valve.This could be tested if you were to do it.At the start and close, and when the valve is at its fullest then move it 180 that would be the lowest point.
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