Cadillac Catera and Cimarron Forum Discussion, Head bolts stretch... Really?? Anyone else ever check?? in Past Cadillac Vehicle Discussion; A Lil confused and a Lil frustrated... So I've read on here and in my 3 volume mechanics manual that ...
Head bolts stretch... Really?? Anyone else ever check??
A Lil confused and a Lil frustrated... So I've read on here and in my 3 volume mechanics manual that the head bolts are a must for changing if ever tampered with because they're made to stretch when tightening and can never be re-used. So please anyone chime in to help me understand what I'm missing... Call it hoarding, but when I was in the middle of my rebuild I kept all the swapped or bad parts on chance they serve other purposes in any field... I took it as obvious truth and never questioned, but tonight I got curious to the amount that the bolts stretched for my own knowledge, and since I goofed and ordered 3 sets of bolts instead of 2, it hit me I could pull one from my new spare bag now and I went digging for the old bags to compare one from each head to the new bag unused...
So each bolt in a row corresponds to the bags and box in a row below it, passenger head bolt, drivers side, then brand new spare... and with a carfax report, another vehicle history party provider, and talking with the previous owner most importantly... The head gaskets and bolts have never been changed. (At 65k miles, I'm the second owner) and I had to change them when it crapped out the day before my birthday. So with them being changed for the first time after 65k miles of use
There is no change... You can't tell the old from the unused... so has anyone compared bolts after a rebuild?? I'd like to know if others actually could see a difference. Otherwise, why keep buying expensive meaningless bolt packages unless you obviously see its bent or stretched... Not really sure which side to stand on for this.
Automobile(s): 2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
East Boston MA.
If the bolts are torque to yield, they have to be replaced. The stretching happens while the bolt is under tension (when it's tight). Once removed, the bolts may not actually appear longer to the naked eye, but the metal has been stretched beyond the limits of its elastic deformation.
Re: Head bolts stretch... Really?? Anyone else ever check??
Moist is correct. Most modern engines are single use torque to yield. On rod bolts we use a stretch guage, on head bolts it is a process of tq to x amount on first pass, then x amount of degrees further the next 2 passes.