TTY head bolt slip up

I had a momentary lapse in attention doing my last 90degree TTY head bolt tightening sequence putting the head on my AHU , while tightening the number 10 bolt I accidently added maybe 35 degrees of additional torque to the number 7 bolt before I realized I was reading the sequence chart upside down. Several expletives later I am hear to ask: is this extra torque on one bolt an issue? Should I redo everything and start over or am I being neurotic? Wish I had some headstuds right now.

35* can be a huge amount of torque added. start the procedure over again, should be fine (hopefully)
They all need to be exactly the same, you can over torque them but thats an area for expert builders. i for one threw it to the wind as added 35 more ft lbs on my ARP because race car and 32psi is lifting the head off the gasket

Head bolts are cheap and I would replace them all. 35 degrees is huge and I wouldn't want that one snapping off. I know you probably don't have a spare set laying around but that is what I would do.

The head studs are very expensive and not worth it unless you have a need, more than just installing a head.

Did the others get the proper torque?

I wonder if that one being overtorqued allowed others adjacent to it to also be overtorqued thereby overcompressing the gasket.

I think I'd start over with new bolts plus a new gasket.

gasket is fine, just replace the one bolt if you want, You can do the math, 125ft lbs plus 1/10 of a turn probably is about 140 maybe 150. procedure for replacing studs are 1 at a time. all you are doing is putting more force on the cast iron block threads, the bolt will not deform before the threads on the block do. I think those bolts are grade 8 or chromemolly, not sure but i dont think you damaged anything. just loosen it back up and torque that one down to 80 then do the same for all the other bolts one at a time. then go up to 90 in the right order, than 125. Drive and park a few times to go though 3 or 4 heat cycles and le the car cool off overnight and re torque them, this might take 2 times to get them fully seated but your not putting out big power so im sure its fine. You just dont want to heat up the engine with an uneven torque. You will know if you fubard the gasket if it has issues over heating and displacing the coolant, then if that happens go though the work of pulling the head again. Unless you still have it apart and its only 12 bolts worth of time, then just start over but the problem here is you have imprinted the head with the gasket, might be better to roll with it. Your call. I dont think redoing the gasket is going to change anything. Its not the gasket, its the clamping force. the gasket, as long as its not cracked or burnt out, its a working gasket and should have no issues.

Mongler98 said:

gasket is fine, just replace the one bolt if you want, You can do the math, 125ft lbs plus 1/10 of a turn probably is about 140 maybe 150.

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The math is not linear, hence the tty bolts. You cannot just take 1/10th of the 125 ft-lbs and add the numbers together. It doesn't work like that.

all you are doing is putting more force on the cast iron block threads, the bolt will not deform before the threads on the block do.

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Yes, they will. They are designed to deform, which is the function of a torque to yield bolt, not the function of the block, which is cast and unyielding.

just loosen it back up and torque that one down to 80 then do the same for all the other bolts one at a time. then go up to 90 in the right order, than 125.

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If the head bolts are loosened, they are replaced. It sucks having one snap off because it was loosened and then stressed in the wrong place upon retorquing. I have replaced head bolts with the ARP studs one at a time, and a few of us on here have when chasing coolant leaks. If anything, remove that one bolt and replace it, the other 9 should hold the deck on straight.

Unless you still have it apart and its only 12 bolts worth of time...

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There are 10 head bolts on his TDI.

One was overdone so adjacent bolts that were properly torqued will see higher load when it is backed off. Enough to be a problem? Probably not.

Gasket damaged by being overcompressed unevenly? Probably not.

Worth a hundred bucks for a gasket, bolts and peace of mind knowing it was done right? Yep.

For me the consequences of a negative outcome would force me to undo the whole thing and start over. The downside of that single bolt breaking would be enough to warrant spending a little more on gasket and new bolts.

Steve

Is it just me?
I would definitely replace the one over-torqued bolt, but if all the others were done right, I don't see a significant probability of trouble down the road. As far as the bolt breaking, you'll find out one way or the other as you have to try and back it out anyway.

Thank you guys I really appreciate the advice. I will have laser focus the next time I do this. All it takes is a second and you are torquing the 7 instead of the 10. I just went ahead and ordered another set of bolts and another gasket. I would rather pay for the peace of mind than worry about it. It might be wasteful but that would suck going back in again.

Yblocker said:

Is it just me?
I would definitely replace the one over-torqued bolt, but if all the others were done right, I don't see a significant probability of trouble down the road. As far as the bolt breaking, you'll find out one way or the other as you have to try and back it out anyway.

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You can't replace one bolt and maintain the appropriate torque sequence, that's the problem with replacing a single bolt.

Pull and start over there's no reason to expect you'll have any failure if the sequence and torque specs are followed.

The risk to me of going on from here and ignoring the torque inconsistency with a potential broken bolt is enough to cause me to take a little more time and money now to undo what's been done and do it again. If it breaks I have to go back in and to be honest I don't really want to have to do that.

It's a gamble that I would not take

Steve

Steve Addy said:

You can't replace one bolt and maintain the appropriate torque sequence, that's the problem with replacing a single bolt.
Steve

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Perhaps. Although if one realizes the mistake before moving on to the next bolt, or if it were to be the last bolt tightened, then I don't really think it would make a big difference to remove the over-stretched bolt and replace it.

I guess we'll never find out as he is planning to start over, but I'd be willing to bet that if he had just replaced the one bolt, he'd be fine.