The Stovebolt Site Forums The Shop Area Engine Shop Torque procedure for 216 cylinder head bolts

Hi, I have my '49 216 cylinder head out getting some valve work done- I found a burnt exhaust valve.
I was talking with my car mechanic about proper torquing of the head bolts when re-installing, and he told me something that sounds weird to me, but he swears it's the way to do it.

Basically, he told me I should torque the all bolts, in proper sequence, in stages, as normal. Then, AFTER they are all torqued to spec, LOOSEN and then RE-TIGHTEN each one by 1/2 turn, using one sweeping motion to loosen and one sweeping motion to re-tighten (again using the correct tightening sequence).
Theoretically, since all the bolts are already tight, no head warpage should result as each bolt is loosened/tightened individually...

Has anyone else heard of this method?? I'm inclined to ignore his advice on this.

Thanks.

That makes no sense at all J. Sound like one of those old wife’s tails like hot water freezes faster than cold. I think if I were you I would smile and give a hardy handshake and say thank you but no thank you and go lookin' for another mechanic.

The torque spec takes the bolt to the proper tension I can't imagine why you would loosen it up then retighten it not using the spec. At the proper torque value the bolt is actually stretched just below the yield point of the material. If you’ve ever taken a piece of metal and flexed it a little, just enough for it to return without distorting it’s original shape then that is what you're doing when you torque a bolt. If you bend that piece of metal a little further and it stays bent then you have gone beyond the materials yield point.
Many manuals will tell you not to reuse head bolts, that you should replace them when you do any cylinder head work. The basis for this is that taking the bolt to the maximum torque can in some cases cause the bolt to stretch beyond the yield point, once you have done that it no longer has the same tensile strength of the original material and will keep loosing strength till it fails. I personally have always reused head bolts and have never had a problem. It would be a different story if I were working on something such as a Winston Cup car where you could not afford to have a failure. Chances are that if you had a bolt fail on your Stovebolt the worst case would probably be a water leak and you would have to replace the gasket.
Denny Graham
Sandwich, IL

I agree with Denny. I would suggest that you don't do it! One thing that I would suggest is that you re-torque the headbolts after you first run it up to temperature. That is very important.

Agreed...loosening, especially a half turn, then re-tightening, after all have been torqued is just not necessary. I'm not sure it would hurt anything, but I don't see where it helps any.
And Denny, I think I know that it's acceptable to re-use head bolts on older engines. Newer style head bolts are made differently, of different alloys, and are intended for one-time use...it's a fatigue thing. Having said that, don't ask me where the line is, or exactly how to tell by looking at them. Seems like the newer style are thinner.
The newest engine I've ever rebuilt is a '74, and that has the old-fashioned "fat" head bolts.

cm

I never heard of that either. I do have to disagree with Denny on labeling the fact that hot water freezes faster than cold an "old wives tale". I got a practical demonstration of that the last cold snap. Both water lines from the mechanical room to the kitchen were left exposed in one area. The hot side froze and the cold didn't. I googled it and found "proof" on both sides of the argument. My evidence is anecdotal I admit but it is a fact that both hot and cold lines were exposed equally (run side by side two inches apart) and the hot froze while the cold didn't. As a side note my bananas (read huge quantity of money and hassle) were saved by the fact that I used PEX for my water lines so the freezing didn't rupture the line.

When observations appear to violate the laws of thermodynamics (hot water freezes sooner than cold), there's something wrong with the data. The "proof" is other people making a similar mistake.

I don't profess to be an expert on thermodynamics but one of the folk who argued the subject admitted that it can happen at times. Times when convection currents in the hot water put more of it into contact with the ambient air more often, possibly leading to faster freezing. He also mentioned the point that hot water has less air in it and air has an insulating property in water. Here is the article in case you decide to read it.

The most important part of torquing any bolt is getting the threads clean and properly lubricared. A dirty or dry thread uses up a lot of the torque overcoming thread friction, so I like to chase the thread in the block with a slightly dull tap to avoid oversizing the thread, followed by a good blast of compressed air, and cleaning the head bolts with a wire brush on my bench grinder. Lube the thread with a few drops of motor oil or 90 weight gear lube, and include a little oil on the surface where the bolt head meets the cylinder head. Be careful not to fill a blind bolt hole with oil, or you'll create a hydraulic lock that keeps the bolt from tightening properly.

I like to tighten head bolts in three steps, for instance, one torque sequence at about 40 or 50 ft/lb, followed by 75 or so, then the full torque of 90 to 100 for stovebolt head bolts. If you use a durable thread lube like Never-Seez, reduce the torque specification by 5 to 10 percent to avoid over-stretching the bolts.
Jerry

Thanks for the advice- it reinforces my own inclination not to mess with the bolts afte rthey are torqued properly. I also learned something new here -from Truckernix- to retighten after reaching normal temperature.

Thanks.

Oh, one other question- I saw a torque wrench on sale for $9.99 at Harbor Freight. The advert says it is accurate to within 6%.
Is that good enough, or should I just put the $100 deposite down at Autozone and borrow their loaner??

I think my engine is worth a little more than 10 bucks. The main concern about a torque wrench is repeatability, and I think I'd rather invest a little more on Ebay or at a pawn shop for a brand-name wrench, even if it's a good-condition used one. Snap-On, Proto, S-K, and a few other recognized brand names will last for generations if they receive normal care. One reccomendation- - - - -if you're using a click-stop wrench, always drop the torque setting to minimum before you store the wrench away. If it's stored with the spring compressed, the calibration can change.
Jerry

Edit: I just checked, and there are over 1300 torque wrenches for sale on ePay right now, including several professional-grade Snap-On wrenches that are probably going to go for well under a C-note.
Jerry

My buddy and I just made the trip to HF this afternoon. You see, we both got our sale flyers yesterday and couldn't think of anything to do today other than spend some money.
Well the only torque wrench he had in his box was an old Sears beam wrench so of course we had to get one of those $9.99 specials. Man, it came in a nice plastic case 20lb to 150lb rated just what the doctor orderd, right?
When we got back to his garage we started to look things over and of course give the clicker a little work out. First off it was just about impossible to get the handle all the way to 150lbs and when we clamped the 1/2" drive in the vice we could just about pull the built in cabinets right off the wall trying to get it to click, it never did. And the lock kept jamming up on it and when we backed it off to about 75lbs it felt to me like it was way to soft. Of course the best way to test it out would have been against the Sears beam wrench but we didn't do that.
If it were me, and I was looking for a clicker torque wrench, I wouldn't bother with one of the HF junkers and I'd do as Jerry suggested. That HF torque wrench would make a great club if you ever had an intruder in the middle of the night.
Denny Graham
Sandwich, IL

Denny, they also make pretty good fishing sinkers, if you're after big catfish downstream from a dam spillway!
Jerry

I would be as careful using (on an engine) a Harbor Freight torque wrench as I would be using a loaner from a parts store (how often do you think that would be calibrated)?

Two years ago, I checked a 5 year old Harbor Freight torque wrench against a newly calibrated Snap-On torque wrench. We did not do a carefully scientific study but the Harbor freight wrench seemed to be about 5 ft-lbs over torque for head bolts.

I like (and use) my Sears "beam wrench" but it has not been calibrated since I bought it about 40 years ago.

Thanks...at least somebody else bought one, and not me! I'll go to Sears when it's time.

If you're not going to do any other mechanical work that you will use a torque wrench for,use the Autozone rental.

Every lug nut, at every wheel change needs to be torqued! I wouldn't be without a good torque wrench, EVER!
Jerry

Exactly; and that is why I bought one.

Torque - Great article in Vintage truck by Patrick Ertle: Vol. 13 No. 6 (Feb. '06); TECH TIPS - The Nuts and Bolts of Good and Tight.

Thanks, 54 5 window!