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| That valve lash adjustment didn't last... https://www.slantsix.org/forum/viewtopic.php?t=64204 |
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| Author: | MadScientistMatt [ Fri Nov 08, 2019 10:14 am ] |
| Post subject: | That valve lash adjustment didn't last... |
I'd recently thrown my Dart on a chassis dyno for some tuning work. Things appeared to be going well when power suddenly started dropping and the engine developed a dead cylinder and began clattering. I pulled the valve cover and found the adjuster on the #3 exhaust valve rocker arm had backed off so far that I had more valve lash than valve lift. I checked the pushrod and confirmed it was not bent, and the adjusting screw had visibly moved upwards. Are there any precautions I was supposed to take to keep the valve lash from loosening up, or is the only real fix new rocker arms? If I need new ones, does anybody know of a good source? Or is there any way to fix a worn one with something like Timeserts? |
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| Author: | MadScientistMatt [ Fri Nov 08, 2019 12:57 pm ] |
| Post subject: | Re: That valve lash adjustment didn't last... |
Update - found a partial batch of NOS rocker arms on eBay, and bought it. |
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| Author: | and739 [ Fri Nov 08, 2019 3:41 pm ] |
| Post subject: | Re: That valve lash adjustment didn't last... |
Slantsixdan explains how to deal with loose rocker arm adjustors in this post: http://www.slantsix.org/forum/viewtopic ... ht=#p72139 I've had to do a few. It's a simple, no-cost alternative. |
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| Author: | SpaceFrank [ Fri Nov 15, 2019 8:58 am ] |
| Post subject: | Re: That valve lash adjustment didn't last... |
You can also use adjusting screws with lock nuts, 3/8"-24 if I recall right. I think I got mine from Summit, but I can't find the confirmation email now. Pretty sure I bought a pack of 16 for a V8. At first I regretted putting them on because they make adjustments that much more complicated, but in a way they make things easier by letting you know quickly which ones you've adjusted already. Just loosen all the lock nuts at first, and keep making adjustments and tightening the nuts as you go. When all the nuts are tight, you know you've adjusted every valve. |
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| Author: | MadScientistMatt [ Fri Nov 15, 2019 9:56 am ] |
| Post subject: | Re: That valve lash adjustment didn't last... |
Thanks, I was wondering about the lock nut possibility. The NOS rocker arm is now on the engine and this project should be getting back on track soon. |
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| Author: | Dart270 [ Fri Nov 15, 2019 1:25 pm ] |
| Post subject: | Re: That valve lash adjustment didn't last... |
If you have new/custom pushrods, sometimes they have a rough surface in the cup and can grind up the adjuster ball. Lou |
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| Author: | MadScientistMatt [ Mon Nov 18, 2019 5:08 am ] |
| Post subject: | Re: That valve lash adjustment didn't last... |
Quote: If you have new/custom pushrods, sometimes they have a rough surface in the cup and can grind up the adjuster ball.
Thanks - that's not the case here, as the pushrods are the same that have been in the motor for the last ~200,000 miles. (At least, that's what I suspect - the odometer is almost at 99,000 and I'm pretty sure it's been around once.) And the screw had visibly backed out. Guess it didn't like the way I was revving the engine on the dyno.
Lou |
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| Author: | Dart270 [ Mon Nov 18, 2019 5:13 am ] |
| Post subject: | Re: That valve lash adjustment didn't last... |
That is very rare to have them back out. Getting good used or NOS rockers should fix it. Other possibility is that you have milled head or used diff cam and the pushrods are too long and that is getting the adjusters past their interference range on the threads. Solution = shorter pushrods. Seems unlikely given your turbo motor specs, though. Happy sleuthing/fixing, Lou |
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| Author: | Greg Ondayko [ Mon Nov 18, 2019 9:22 am ] |
| Post subject: | Re: That valve lash adjustment didn't last... |
I once had this happen to me on a milled head, I was impatient, dumb, cheap, etc so I shimmed the rocker shaft up using some scrap sheetmetal from a door so maybe ~.050" shims were used between the rocker stands and the shaft itself.. That was probably ~60,000 miles ago in 2007-2008 on my daily slant six driver. I do need to adjust the valves again. I know some would not recommend this technique, but ot worked for me with a stock cam I don't think the Geometry suffered too much. Greg |
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