It might be difficult to actually see the damage, but the idea is that the rocker nut would be turning down on the stud further than it should be - caused by previously overtightening to 40 ft lb. I suppose you might see some damage to the threads in the nut or to the stop surface on the stud.


But what do you mean by stripped? Are the corners of the hex on the bottom of the stud rounded off - or are the threads where the stud screws into the head damaged - or are the threads where the rocker nut screws on damaged?


Please advise...

 

The corners are rounded off on the exhaust valve on #2 cylinder.

 

Are you using a 12-point deep socket? If so, a good quality 6-point deep socket will catch the corners of what is left and take it out. There are other options as well. let us know.

Here's one of the best - see the 6-point drive
https://store.snapon.com/Deep-inches...t-P631458.aspx

Yeah, I know it's priced beyond unreasonable. I used to have all Snap-on tools when I was working in dealerships, but no more. Just used it for the photo. Try Craftsman (Sears/Ace Hardware)

 

Thses things are best, work every time https://www.lowes.com/pd/IRWIN-BOLT-...r-Set/50146292

 

I seriously doubt if you could have damaged the upper end rocker stud threads by over-tightening the rocker nuts by a mere 20 ft.Lbs. Those studs are far and away much stouter than the rocker nuts. On the other hand, a partially stripped and/or damaged rocker nut (due to over tightening, as Less mentions) could possibly result in a overly tight valve clearance (i.e. a severe loss in compression). Therefor, I'd recommend replacing the stud nuts as a first resort.

Beyond that, I would again suggest that one, or both, lifters in the offending cylinders are internally stuck at full height/length. This possibility could, of course, result in valve clearances that are so tight as not to allow the valves to seat fully at TDC of the compression stroke (which would again, explain why you have zero compression when the rocker nuts are tightened to specs, yet good compression returns when you loosen said rocker nuts). A cylinder leak-down test would confirm this possibility (you might be able to borrow or rent a leak-down tester at one of you local auto parts stores).

 

ok I used a Stanley's 5/8 spark plug socket 6 point, it broke the others just fine. What other options do I have ?

 

Should I do the leak down test after I replace the rocker studs ?

 

https://www.lowes.com/pd/IRWIN-BOLT-...r-Set/50146292

 

Is it possible that your socket cracked and that is why it is now slipping? 6-points don't usually round things off. Option would be to use a different socket or something like Newguy is suggesting or an actual stud remover. Can you please take a photo of the damaged rocker stud?

 

I'd perform a leak test before and after. But again, I think you have one or more internally stuck lifters on each of the offending cylinders. I, of course, could be wrong tho. However, replacing the studs and nuts isn't that expensive or time consuming... So, yes, I'd go ahead and do a leak down test with both the old and new rockers. If the before and after leak down results are the same (i.e. no comp with the nuts torqued, and comp is restored with them loosened), then I'd go down the path of stuck lifters. At that point you could either go through the trouble and expense of replacing the lifters (be sure that you use the 'non-adjustable type), or you could try some of the 'unconventional' and possibly risky methods of freeing them up while they're still installed. We can talk about that later tho. Also be sure to follow the leak down test procedure exactly as per the instructions with the battery disconnected (you will need a compressor for this btw).