2.3L ('83-'97) Head bolt torque -- how bad did I screw up?

[SenseAmidMadness]

Made a silly mistake in swapping my 1995 2.3 head gasket.

New Fel-Pro head bolts and head gasket. Threads were dry with no sealant though the bolt holes weren't perfectly dry.

I accidentally read an older service manual and torqued all the head bolts in 2 stages to 50 and then 90 foot-pounds.

Looked it up, and Fel-Pro as well as a ton of other places say I should have done the revised torque spec of 51 foot-pounds and then 90 degrees.

How big of a whoopsie? Do I need to get another set of head bolts and another head gasket and try again?

 

[SenorNoob]

So the real question is why was the spec changed?

Are different bolts listed for the earlier spec?

 

[SenseAmidMadness]

So the real question is why was the spec changed?

Are different bolts listed for the earlier spec?

I believe so, yes. Forum wisdom says that the original bolts were not torque to yield and could be reused, and sometime in the 90's a new TTY bolt replaced it.

 

[pentode]

If they are indeed TTY, I'm sure most people would say get a new set and try again.
This is probably terrible advice so take it with a full pinch of salt. I'm thinking that with 90 degrees, your final torque is going to be a fair amount higher than 90 pound feet. My gut tells me those bolts are probably still fine. If I were in a pinch or feeling brave, I'd be tempted to just do the procedure again. I usually chicken out though. Let's get some guru feedback here.

Edit: unless the procedure specifically forbids it, I'd definitely very lightly oil the threads and under the bolt heads.

 

[scotts90ranger]

It's probably a wash either way considering if you're staying stock power output... but if you're worried you could back the bolts out one at a time until they're loose then just go to the TTY spec... if I had to guess the TTY spec is tighter than standard so you're most likely safe using the bolts again...

 

[19Walt93]

If they're torque to yield bolts, don't reuse them. They're meant to stretch during the 90 degrees and they may break or not torque properly a second time. A new gasket would a good investment, too.
I'd hate repeating the job, too, but I'd hate it worse if I had to extract broken headbolts from the block.

 

[alwaysFlOoReD]

I would loosen one. Mark the head and beside with a paint pen first so you can see the orientation before and after. Then torque using the 90°. If the mark lines up or goes farther I would reuse.
Oiling will allow greater stretch with the same torque. Find out if its supposed to be oiled or not...
In other words not oiling may have saved your butt if its supposed to be oiled.

 

[RobbieD]

In other words not oiling may have saved your butt if its supposed to be oiled.

Which begs the question . . . what weight butt oil do you recommend?

And, do they make a synthetic for that?

Inquiring minds want to know . . .

 

[pentode]

I'm following up because I think this predicament is a great chance to learn something and I always love to hear from the techs who have done these jobs dozens or hundreds of times.

The procedure alwaysFlOoReD suggested is basically exactly what I had in mind. Obviously the main fear as Walt pointed out would be breaking a bolt. My thought was that whether the stress on the steel increases linearly or exponentially as torque increases (I don't know), and given that the breaking point for a typical bolt has gotta be at least 50-100% beyond what the actual final torque spec is (you would think, given normal engineering practices), that the bolt shouldn't have suffered too much if it was _under_ torqued.

So, how often do these things actually break in practice? Does anyone have any real world data? Genuinely curious.

 

[19Walt93]

My shop broke zero because we never reused torque to yield bolts. Give it a try if you feel lucky, if it doesn't work: I told you so.

 

[alwaysFlOoReD]

My shop broke zero because we never reused torque to yield bolts. Give it a try if you feel lucky, if it doesn't work: I told you so.

And if I was a shop I would have the same policy. But I'm not. I've been poor my whole life and sometimes have to gamble... Its paid off more times than it hasn't, but I also try to minimize the risk by thinking thru the procedures and consequences. In some cases biting the bullet is best. In this case I think what I outlined is a viable test to see if the bolt has been torqued to yield or not...

 

[Curious Hound]

And if I was a shop I would have the same policy. But I'm not. I've been poor my whole life and sometimes have to gamble... Its paid off more times than it hasn't, but I also try to minimize the risk by thinking thru the procedures and consequences. In some cases biting the bullet is best. In this case I think what I outlined is a viable test to see if the bolt has been torqued to yield or not...

I agree. The test always FlOoRD mentioned willtell if they are currently undertorqued and, if so, bringing them up to torque won't hurt anything.

 

[19Walt93]

And if I was a shop I would have the same policy. But I'm not. I've been poor my whole life and sometimes have to gamble... Its paid off more times than it hasn't, but I also try to minimize the risk by thinking thru the procedures and consequences. In some cases biting the bullet is best. In this case I think what I outlined is a viable test to see if the bolt has been torqued to yield or not...

Have you confirmed that the bolts are in fact torque to yield? If they are it's not worth the gamble.

 

[19Walt93]

I just reread your original post. If the gasket came with new bolts it's safe to assume they are torque to yield and the way you installed them might make it safe to try retorqueing them- just maybe go a little less than 90 degrees this time.

 

[SenseAmidMadness]

For everyone speculating: Fel-Pro head bolts, part number ES72137, are absolutely torque-to-yield. The slip inside the box specifies 51 foot pounds and then 90 degrees. See pics below for what one looks like after it's been torqued to the full spec. I certainly would not reuse them after that 90 degree step.

Supposedly these Fel-Pro bolts are the equivalent of the updated OEM bolt from somewhere around 1994-on, but I don't know that for sure. The only ones I know of that aren't TTY now are the fancy ARP studs and nuts and those are $155 a set...yikes! I don't blow enough head gaskets to justify triple the cost from the parts store (and a ton cheaper on RockAuto...)


I bought a second set of these same Fel-Pro head bolts but ended up not using them...after opening the package and thus making them non-returnable. D'oh! Spares for next time I guess.

If they are indeed TTY, I'm sure most people would say get a new set and try again.
This is probably terrible advice so take it with a full pinch of salt. I'm thinking that with 90 degrees, your final torque is going to be a fair amount higher than 90 pound feet. My gut tells me those bolts are probably still fine. If I were in a pinch or feeling brave, I'd be tempted to just do the procedure again. I usually chicken out though. Let's get some guru feedback here.

Edit: unless the procedure specifically forbids it, I'd definitely very lightly oil the threads and under the bolt heads.

You turned out to be completely right here. 90 foot pounds and 90 degrees are quite different! Proof below!

I would loosen one. Mark the head and beside with a paint pen first so you can see the orientation before and after. Then torque using the 90°. If the mark lines up or goes farther I would reuse.
Oiling will allow greater stretch with the same torque. Find out if its supposed to be oiled or not...
In other words not oiling may have saved your butt if its supposed to be oiled.

This is a solid idea and I decided to go one step further than a paint pen -- I used my angle torque gauge and took pictures. Just in case anybody else ahead of me makes this same mistake.

First I removed the head bolt that's listed as #1 in the tightening pattern. I know from experience that used TTY bolts have visibly yielded threads, with the overall thread form no longer being a 60 degree V shape and more of an N shape. Hard to catch on camera but definitely visible to my eyes. Here's a comparison:

Hopefully you can see that in the picture. The darker and more oily bolt on the right is the one I pulled out when starting this job. It was torqued to 51 foot pounds and then 90 degrees...about 60 thousand miles ago.

By comparison the other bolt, having been torqued to 50 foot pounds and then 90 foot pounds then removed, looks downright new. Thread form still looked like a perfect 60 degree V to my eye with no deformation. At this point I felt comfortable reusing it, at least for the experiment in the next step.

Here's what I did. I lightly oiled the threads of the "new" bolt that hadn't been torqued to yield. Then installed it and tightened to 51 foot pounds. See below for its position at 50 foot pounds. 210 degrees on my gauge.

Now see where its position was when the torque wrench hit 90 foot pounds:

Went from 210 on the gauge to just under 260. Only 50 degrees! About half the rotation called for. No wonder the bolts hadn't yielded yet. Head gasket likely wasn't properly squished either.

Given this information I decided to reuse all the head bolts that were already in there. Tightened the one seen in the experiment until it reached 300 degrees on the gauge. Removed the others one at a time, lightly oiled the threads, and did them each up to the proper spec of 51 foot pounds plus 90 degrees. There weren't any strange noises or other signs from the Omnissiah that I had sinned and none of them snapped, so I'm gonna call it a success (pending the results of the first week's driving when it's all buttoned up).


I think it'll be okay. This is a mostly stock engine with a stock roller cam going back in it. Only thing that isn't stock is the valves, seats, and springs.