MelloYellow

Any reason not to hit the head bolts at 100-120 ft/lbs if there is no problem? My full time C5 mech does his heads this way ALL the time. Has never broken a bolt, cracked the block or blown a gasket or lifted a head.

Just curious what might be bad about 100-120 ft/lbs on head bolts.

Thx

Terry Burger

iTrader: (4)

The head will cup if you go too tight, not to mention the head gaskets are made for a specific amount of preload.

MelloYellow

My mech is buying some kinda crazy digital measurement snap-on TQ wrench. He wants to take the GM method to a test block and go 22, +90*, +90*, +50* and see what it really comes out at.

No probs so far with the 100-120ft/lbs here on 100+ engines. Where/when do you think it'd show up? No gasket issues either. He's been doing this for 5 years+ on LS1's.

AlonzoVersion 1.0

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MelloYellow:
<strong>My mech is buying some kinda crazy digital measurement snap-on TQ wrench. He wants to take the GM method to a test block and go 22, +90*, +90*, +50* and see what it really comes out at.

No probs so far with the 100-120ft/lbs here on 100+ engines. Where/when do you think it'd show up? No gasket issues either. He's been doing this for 5 years+ on LS1's.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Well so long as it works and doesnt hurt then why not.

LS1derfull

i JUST SWAPPED HEADS AND CONVERTED TO HEAD STUDS, AFTER SEEING the condition stock bolts leave threads in block, i wouldnt recommend anything but studs. Bolts rely on perfect threads (no resistance) to reach proper stretch, my blocks threads couldnt provide this, and now im safe to swap out heads with out hydraulicing block also.
ARP has great kit, and for $220 i will save block in the long run, good deal IMO.

Max@Cartek

Going to a higher torque spec isn't necessarily better. What you are looking for when you torque down a set of heads is for a certain amount of bolt stretch which is what holds the heads to the block. that's why sometimes torque specs change when you change bolt types(ex: ARP bolts). The reason it changes is because of the metal composition difference. So when you over-torque you may exceed the tensile stregth of the bolt causing bolt breakage. Furthermore just over tightening may cause weird clamping forces(an over stretch of the bolt may result in less clamping force do to the exceediing of the elasticity of the bolt) and premature fatigue to a bolt. Always follow the specs of the bolt manufacturer, they know best. It's not a matter of tightening it more in order to more securely fasten the head to the block.

Max

Fireball

iTrader: (21)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Wide Open Throttle:
<strong>. So when you over-torque you may exceed the tensile stregth of the bolt causing bolt breakage. Furthermore just over tightening may cause weird clamping forces(an over stretch of the bolt may result in less clamping force do to the exceediing of the elasticity of the bolt) </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">FYI...Stock head bolts are torque-to-yield...you exceed the limit of elasticity when tightening them...but there is still an increase in clamping force, it just won't return to the unstressed state after unloading (thats why they must be thrown away). I'm unsure how far into the plastic region GM designed these headbolts but if you overstress them past the ultimate limit, the clamping force actually reduces and integrity is severely compromised <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

Max@Cartek

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">FYI...Stock head bolts are torque-to-yield...you exceed the limit of elasticity when tightening them... </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I'm aware of that. When mello yellow mentioned torque specs I thought he was speaking about ARP bolts or the equivalent.

Just torqueing down on a Torque to yield bolt is not accurate enough. You would have to use a torque angle meter and figure out what the torque value for it is once you've reached the correct angle. This is inaccurate because it all depends on what type of lubricant(ex: moly vs something else) you use when you tighten down the fastener. So torque values may vary depending on assembly.

rumbleme

I agree with WOT. If you need documented information visit SPS - Unbrecko, they have a detailed explanation of fasteners.

Fireball

iTrader: (21)

WOT I figured you knew that but I just clarified based on Mellow's post mentioning trying to relate GM's angle method to a torque reading <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

felton316

Can you still remove the heads (with motor mounted in the car) when using studs? I've played with some cars where the studs prevent removal of the head while the motor is still in the car. I wound up having to take out the studs every time.(What a pain in the ***) Just wondering if this is the same on the camaros?

Thanks,

BYE RICE

iTrader: (2)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by felton316:
<strong>Can you still remove the heads (with motor mounted in the car) when using studs? I've played with some cars where the studs prevent removal of the head while the motor is still in the car. I wound up having to take out the studs every time.(What a pain in the ***) Just wondering if this is the same on the camaros?

Thanks,</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">It's a pain in the *** as it is,let alone with studs.Studding the block on an f-body would pretty much mandate lowering the engine assembly /cradle from below before removing installing the heads.(About two hours with 2 competent folks)Well worth the effort if you have the means.(A lift).

<small>[ June 03, 2002, 07:13 PM: Message edited by: BYE RICE ]</small>

Scalpel

iTrader: (4)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MelloYellow:
[QB]go 22, +90*, +90*, +50* and see what it really comes out at.

/QB]</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The additional 50* turn is only for bolts 9 and 10 of the torque sequence (the two shorter bolts).

383LQ4SS

iTrader: (33)

I have ARP head studs on my motor and removing the heads is much easier with them. Once the nuts are all off...just lift the heads out. Clears everything with ease. Ive done both stock head bolts and studs...studs is the way to go. And thats just for removal. Install and Tqing is a dream with studs. And your left with the feeling that the Tq is dead nuts on as well, unlike stock head bolts.

Scalpel

iTrader: (4)

Where do you get the studs? Thanks.

MelloYellow

Jegs or Summit has them.

I'd like to focus on Stock Bolts at 100-120 ft/lbs. If they can take it, why not? I acknowledge some of the concerns posted above, but the technique seems to be working well for my C5 mech. Any other experience/comments to the idea welcome.

He plans to use a special TQ gauge to measure the GM angle/turn technique sometime in the future. He has lots of spare blocks lying around. Hydrolocked mostly. Gotta love snorkel air filter mods.

Scalpel

iTrader: (4)

Do you still tighten the studs to 22 lbft and then the additional 90*, 90* and 50* (on bolts 9 & 10)? Thanks.

MelloYellow

I'd check a diff thread, but ARP studs have diff TQ specs I believe. No need for the GM stretch bolt TQ sequence.

Me? We just hit the stock bolts to 110# or so.

Scalpel

iTrader: (4)

And what's the pro/con of using studs instead of TTY head bolts? Thanks for all your help, Mellow.

C5 Tweaker

Mello,

You can use a simple torque spec with the ARP, but it would not be appropriate to do so with the stock torque to yield bolts.

The relationship between stretch and torque is VERY non-linear. The torque almost does not change in the last 90 degrees of turn. This is the reason for the torque/angle spec. They would make it easier if they could.