When I knew I was going to be building an engine, I knew I had to buy a torque wrench. So after looking around I noticed they can get quite pricey. I also noticed that Harbor Freight had then for what seemed like a too-good-to-be-true price. So I bought it. I used it on wheels and what not, It seemed fine.

So tonight I decide to work on the engine. The next step in the process was to bolt down the heads. I read the FSM and set out to properly tighten my head bolts. The first step is to tighten them all down to 72 ft. lbs. So I set the torque wrench and got going. I began tightening and thought to myself "Damn, that seems really tight."

I went over to my workbench and clamped the 1/2 inch drive into the vise. I measured from the center of the drive to the end of the wrench and got about 15.5 inches, 1.29 ft. So I set the torque wrench to 72 ft. lbs. and filled a bucket with bricks and water to a weight of 55.8 pounds (55.8 * 1.29 = 72). So I hung the bucket from the torque wrench 15.5 inches from the center of the 1/2 inch drive, making sure the wrench was parallel to the ground.

It clicked just as I put the entire weight of the bucket on the wrench.

"Great." I thought, "This thing is spot on."

I preceded to tighten three head bolts, and everything was fine. Although I kept thinking that I was tightening them too much. I kept reassuring myself that I just tested it and the torque wrench was fine.

So on the fourth bolt, after tightening for what seemed like forever, I heard a very ominous "SNAP". The bolt snapped! So I backed out all of the bolts and took the head off. The end of the broken bolt was just about flush with the top of the block. To my amazement, the end of the bolt in the block twisted out without much trouble using a pair of pliers. So it obviously was not bottomed out. I was slightly worried this was the case because I used HR head bolts in my vq30de block. The HR bolts have a few more threads then the originals.

Once I pulled the bolt out of the block, I measured it with the calipers to see if it had stretchered. Sure enough, the bolt showed significant necking near the break area.

So what happened? I think that even though my test showed the torque wrench to be accurate, when I was tightening the head bolts I was doing it very slowly, a little at a time. I think the mechanism inside the torque wrench just isn't that great and causes the torque to rise above the selected setting if the torque you are applying to the wrench is only slightly about the selected torque. Kind of like there is excess friction or it is just poorly designed/manufactured. I never noticed this problem before because I have never been so careful in using the wrench.

So in the end it seems I'm only out the money I spent on the wrench, and the four head bolts that I started to tighten. The engine itself seems to be fine. I can run a good bolt in and out of the all the holes. Next time, however, I will be using a better wrench.

 

I bought a beam type torque wrench from Sears this morning and used that to check the calibration of my HF click type. I checked 30, 50, 60 and 70 ft. lbs. and the Harbor Freight wrench clicked where it should, each time. So it seems to be accurate, however, maybe not that precise.

I also used Red-Line assembly lube on my head bolts and not new motor oil, as the FSM suggests. If the assembly lube is better performing than engine oil, this might have the effect of lowering the torque on the fastener.

All in all, I would buy the HF click type torque wrench again, but for anything requiring a high level of precision, I'm convinced the beam type wrench is better because there is no mechanism to add friction and skew your torque settings. I was able to install the other head using the beam type wrench without incident.

 

As I read your original post, I was wondering if you had a bad bolt. I would think that a case hardened bolt would be able to take a lot more force than 70 lb ft. You would strip the threads before the bolt would break. Again, that is what I think.

But the fact that you didn't have any damage to the block is good.

 

Man that sucks donkey! I also used the HR bolts, But it says tighten to 79ft/lb the loosen completely, not 72ft/lb...THEN retighten all bolts to 29ft/lb, THEN and additional 90* x 2, so yea, if this bolt couldn't handle even 72 ft/lb, it must be a bad bolt. Did you test the wrench with the heavy bucket again after to check calibration or no?

 

Did you use 75w90 on ALL surfaces (both sides of the washer, head of the bolt, head, and the threads? Did the bolt rotate smoothly through it's torque sequence, or did it pop/jump? Many times, false TQ readings can be attributed to lubrication issues. TQ wrenches are seldom off more than a few ft-lbs.. even the crappy ones. Or, it might just be a bad bolt. However, it looks like you just exceeded the plastic region of the bolt, stretching it.

BTW, I sent you a PM regarding those VQ swap cam signal inverters.

Thanks,

Travis

 

i love harbor freight but when it comes to precise tools i dont trust them for anything. the old saying you get what you pay for comes into play big here. id much rather pay the extra money for a sears torque wrench rather than have an inaccruate torque.