Cylinder head bolts

[opentrackerSteve]

Thanks for the replies. Ponyman66,

My torque wrench doesn't have a locking mechanism, you pull the bottom of the handle out and twist to set it. I too am very, very familiar with torque wrench calibration. We must do that for even RF connections when assembling our radars and installation of equipment in our test aircraft....

 

[Ponyman66]

Thanks for the replies. Ponyman66,

My torque wrench doesn't have a locking mechanism, you pull the bottom of the handle out and twist to set it. I too am very, very familiar with torque wrench calibration. We must do that for even RF connections when assembling our radars and installation of equipment in our test aircraft....

Familiar with the type you are talking about, I have one of the same style in addition to several twist lock style. The only style I don't own (nor have ever owned!), is a beam or dial type. I really need to finally break down and get one!

BTW, I was actually sent to the Snap-On school when I was in the military. I was in aviation as an electrician but was working in the quality assurance office at the time. Not only were we tasked with primary QA on the aircraft, NDI and fluid analysis (oil monitoring), but we also insured all precision tools were calibrated. I raised hell with the Government/military sales rep from Snap-On about how we could never get service or repairs from him (receiving visits only when he came around to push a new product!). I threatened to use the local retail rep and made arrangements to do so. He decided he'd employee a little better customer service and set us up with several schooling spots at their repair facility to try to smooth things back out! That's how I got to attend the torque wrench cal/repair training!

p.s. As a comment for everyone, a big confusion folks often make is checking the calibration versus actually calibrating a torque wrench. The example Midlife posted is actually a check of the calibration.

 

[GypsyR]

This thread bothers me. If three bolts snapped during the torque procedure I would personally have zero faith in the rest of them holding up to service. Generally speaking ARP sells very high quality stuff and I wouldn't expect this sort of issue with their head bolts. I would if someone was trying to reuse torque-to-yield head bolts but this isn't the case. I feel like there's some missing info in here somewhere. It's a good idea to lube the washers and bolt heads but you shouldn't have to, IMHO . Is this an early 289/302 or later "5.0"? Some say it makes no difference but about 1993 Ford starting using torque-to-yield (OK, "stretch" bolts) on their 5.0 engines. The stretch bolts are less tolerant to over torquing. Pretty sure ARP doesn't sell those as replacements but they might be in their catalog, I haven't looked for them. The various replacements I'm familiar with from ARP are "regular" bolts. Rule of thumb passed on to me from the local seriously expensive engine builder is to torque all new head bolts to about 20 foot pounds five times. This makes sure the threads seat so when you go for the real torque you are in fact measuring bolt stretch and not excessive thread resistance. Lastly, I don't know what spec you used but my rule of thumb torque for 302/5.0 aluminum heads is oil on the long bolt threads and sealer on the short bolts. Then torque all in increments. 35 ft.lbs. Then 50. Then 70. The the longer inner bolts only another 10 foot pounds. 351W 1/2" bolts go: 35, 70, 100, and then another 10 pounds on the long ones.
Speaking of 1/2" bolts, it's very common for alloy heads to have 1/2" holes. When used on engines requiring 7/16" bolts you are supposed to use reducing adapters in the heads or special stepped bolts. I can see breaking 7/16" bolts when trying to torque them into 1/2" holes, way too much sideways give there.
I've moved up to a digital torque (price still makes me grit my teeth) because of the added angle torquing ability. Plus it's really neat. It's getting a little older now and you guys have got me wondering about a calibration check on it. Think I'll ask about that.

 

[opentrackerSteve]

engine is 1968 302 block. what you cited is exactly how I tigtened them. 'Then torque all in increments. 35 ft.lbs. Then 50. Then 70. The the longer inner bolts only another 10 foot pounds'

 

[Horseplay]

His concern, Steve, is that the other bolts would have suffered just as much stress as those that broke but managed to avoid snapping. Down the road after all the stresses of operation and temperature fluctuations they may give out. One does have to be bit concerned if you think about it. ARP bolts are about as good as it gets both in strength and consistency. My guess is your wrench was quite a bit off and/or your technique varied from those that broke to those that held. Either way...not exactly confidence inspiring.

Hopefully all is good and nothing to worry about.