Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

[rs2k]

I replaced the head gaskets on one of my 350s today. Cylinder 3 had blown out into cylinders 1 and 5. I always torque the head bolt down in three stages. 25 Ft-Lbs, 50 Ft-Lbs, then 65-70 Ft-Lbs. Everything seemed to be going just fine until I got to the last stage. My 1/2 inch to 3/8 inch reducer broke while torquing down the bolt between cylinder 1 and 3. I was around 60 ft-lbs at the time and thought the bolt had stripped at first. I got another reducer and continued to tighten down that bolt, but it almost seemed reluctant to torque. It took longer than the other bolts to get to 65 Ft-Lbs, and when I held the torque wrench at 65 Ft-Lbs it slipped down to 60 Ft-Lbs. I kept trying to tighten the bolt and it kept wanting to stay at 60 Ft-Lbs. It almost seems like it has a slipping helicoil. I went ahead and left that bolt at 60 Ft-Lbs and continued assembling the rest of the engine. I was afraid to break something that seemed to be within specs. Could the breaking of the reducer have caused an over torque to that bolt? Could the bolt be stretching and getting ready to snap? I am tempted to remove that one bolt, but I don't want to break the bolt if it's going to be OK as it is now.

Any ideas on what I should do?

I do plan on running the engine tomorrow to see if it's OK now.

I also just about broke my thumb when I dropped the exhaust manifold on it. Half my finger nail is black and I have a nice little split in it. My hand also feels like it's going to fall off. Any idea's on how to fix that?

 

[Howard Sterndrive]

Re: Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

calibrated your torque wrench lately?
60 ft. pounds shouldn't break a reducer.
Even a 3/8" to 1/4" could take 60 ft pounds.
That bolt yielded (stretched beyond it's elastic range).
You have to take it apart again. That bolt isn't providing any clamping force.
Don't run it like that.

 

[rs2k]

Re: Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

This is a brand new torque wrench, albeit the cheap bending type. It was also a cheap reducer. I've broken them before torquing cylinder heads. The joint starts to twist and will eventually twist all the way off. This same reducer torqued 8 other bolts down to 65 - 70 Ft-Lbs and all 17 to 50 Ft-Lbs. If finally failed on number 9 at around 55 - 60 Ft-Lbs. I torque very slowly when I use the cheap wrenches. I'm pretty sure about these numbers.

Not that I'm any where near as accurate as a cheap torque wrench, but it felt like 70 Ft-Lbs to me when I was torquing it on. I've replaced plenty of cylinder heads, I've just never had a problem with a bolt.

I also checked the block and heads for warpage. I couldn't detect any warpage with a .0015 feeler gauge.

 

[rs2k]

Re: Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

All the other torqued fine, can't I just replace the one bolt?

 

[Rocky_Road]

Re: Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

All the other torqued fine, can't I just replace the one bolt?

I would definitely replace the one bolt.

And I would eliminate the reducer, and use the correct 1/2" drive socket.

Given that the reducer had to be 'bending' prior to failure, I would question the torque on all the bolts. Using the correct (not reduced) socket, I would check all of them!

Just my $0.02...not worth a 'plug' nickel.

 

[rs2k]

Re: Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

I did go back over each bolt after getting them all torqued, but I will get a 1/2 inch 5/8 socket and a new bolt before I fire up the engine. Chevy or not, after doing a lot of reading I think I will also get new cylinder head bolts the next time I replace a cylinder head.

 

[rs2k]

Re: Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

Because of the engine location and the hardness previous gaskets, it took me all day, a sore back, and a busted fingernail to get these gaskets replaced. I'm not looking forward to doing that again tomorrow, but I will if that's the only solution to me. I'm not one to second guess any move I make, but I do wish I would have got new cylinder head bolts. I would much rather just replace the one bolt and be done with it.

Of course, it would be easy to replace just one bolt at a time. What if I were to replace every head bolt one at a time? I would feel better about having all the head bolts replaced, but I don't want to spend another day earning a small piece of mind. I'm sorry if I sound lazy, I'm just really sore and won't be able to use my good hand in any way worth while for a few days.

 

[windsors03cobra]

Re: Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

Do yourself a favor and throw that beam type torque wrench in the weeds and spend $65 on a crapsman click type torque wrench, I would spend another $35 on some sockets to use on it. That reducer is a no no IMO. I use a reducer and or an extension only in where absolutely necessary.

 

[Howard Sterndrive]

Re: Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

As a veteran mechanic, I have felt that sick feeling of a fastener yielding a few times.
Not once have I ever seen the "just back it up a bit" method working.
Bolts are like delicate elastic bands.
They have a very small range of stretch where they will try to clamp things.
Too much stretch and they began to plastically yield- meaning they have permanently deformed, necked down a bit, and are clamping nothing.

Head bolts are goofy things- the sealant they require is slippery and can cause a lot of extra stretch per the amount of torque.
We measure torque, but what we really want is stretch.
On very big diesels, they use head studs...they pull the stud with a hydraulic stretcher to a certain dimension, wind the nut down finger tight, and let the stud relax....perfect head clamping every time... no torque wrenches allowed.

I have a $9 flea market beam type torque wrench that I rarely use but often check on the snap on calibrator we have at work (usually after someone calls me out on owning it). And every time it is 100% bang on. But I can imagine some cheapies are not accurate at all.
So I wouldn't toss the wrench just because it's beam type, but I would certainly test it against other torque wrenches at the very least.

There was a study done with experienced mechanics where they were asked to torque various size fasteners without a torque wrench. The more experienced the tech, the more overtorqued the fastener. Most techs were 50% too high going by feel.

No one likes to disassemble something they just assembled, but doing so ultimately distinguishes a technician from a grease monkey.

Knowing in your heart it isn't right means you gotta open it back up.

Start by taking that 1 bolt out and seeing what the threads look like (hopefully not half peeled off)....it could be the threads in the block...and if it is, it really has to be fixed.
There are no extra head bolts just for insurance.
Each and every one of them has to provide the proper clamping force for the gasket to seal.

It might work for a day or two with one bolt out, but the head is holding in 4 chambers of compression and "explosions" of fuel and air being lit.. there's a lot of pressure, heat, and vibration....

 

[Bondo]

Re: Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

Ayuh,....No way I'd run it, til you figure out Why that bolt is a Problem...

 

[rs2k]

Re: Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

That bolt yielded (stretched beyond it's elastic range).
You have to take it apart again. That bolt isn't providing any clamping force.
Don't run it like that.

100% correct! I just pulled the bolt and it gave way at only 40 Ft Lbs. Upon inspections it's quite obvious that the threads above the sealant have stretched. I will be replacing all the bolts today one at a time. I am also getting a 1/2 inch 5/8 socket for the torque wrench.

 

[rs2k]

Re: Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

The bolt I pulled looks very similar to the bottom picture on this page:
http://scuderiatopolino.com/scuderiabb/viewtopic.php?f=30&t=178

 

[rs2k]

Re: Odd feeling cylinder head bolt while torquing cylinder head onto Chevy 350.

The head gasket just happened to fail its worst under that bolt. I made sure to use the same bolt from the hole it came from. That could have been the original cause of the head gasket failure.