is it ok to reuse factory head bolts
10-10-2009, 07:36 AM
#25
I appreciate you pointing out some of this info.
I just want to make sure I have the "bottom line" correct here...it isn't like I've never had bad information before
.
So you are telling me that...GM bolts are better for a 200,000 mile motor than the ARP (or any reusable) head bolt is. Correct?????
I just want to make sure I have the "bottom line" correct here...it isn't like I've never had bad information before
.So you are telling me that...GM bolts are better for a 200,000 mile motor than the ARP (or any reusable) head bolt is. Correct?????
10-10-2009, 07:40 AM
#26
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A friend of mine who is an A mechanic for a Chevy dealer told me the block itself is only suppossed to have head bolts installed in it a limited number of times. Now I have no other confirmation on this and I post it in hopes somebody can confirm or deny this. This would be another good reason for studs as the threads in the block do not see the turning forces and simply act as an immobilized anchor.
10-10-2009, 08:43 AM
#27
If you are building a NA car or light on the nitrous, GM bolts are fine. If you are racing, putting a big shot or blowing on it with a lot of boost, ARP is probably a better choice.
I get the GM head bolts for $36.00 for both heads, ARP bolts are $143, studs over $220. You better be racing or pulling the heads off a lot to cover the cost for no added benefit.
If look at ARP's instructions on bolt stretch it is not a lot different than torque to yield. You are stretching a bolt to a predetermined length to provide a specific clamping force. The GM TTY system is doing the same thing but the bolts are not reusable per their specifications. Their fastener engineers determined that if a specific bolt is tight x amount of degrees of a specific sequence a predetermined clamping force will be applied. If the LS7, stock and modified, can stay together with the GM fasteners I am sure 90% of the engines on here will be just fine.
I have not checked the LS9 to see what they are using but it would be nice to know.
I get the GM head bolts for $36.00 for both heads, ARP bolts are $143, studs over $220. You better be racing or pulling the heads off a lot to cover the cost for no added benefit.
If look at ARP's instructions on bolt stretch it is not a lot different than torque to yield. You are stretching a bolt to a predetermined length to provide a specific clamping force. The GM TTY system is doing the same thing but the bolts are not reusable per their specifications. Their fastener engineers determined that if a specific bolt is tight x amount of degrees of a specific sequence a predetermined clamping force will be applied. If the LS7, stock and modified, can stay together with the GM fasteners I am sure 90% of the engines on here will be just fine.
I have not checked the LS9 to see what they are using but it would be nice to know.
05-05-2018, 10:27 AM
#32
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05-06-2018, 09:46 AM
#34
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Robot Engine Assembly OR Human Hand Hi ALL, I see EVERYONE here "missed" the FACT that GM engines are assembled by ROBOTS.
THUS they are not built to "feel" a bolt stretch as can the Human Hand.
I ALSO state Rod Bolt Life is measured by length increase. (new/used)
WHO can state the difference between the Head Bolt/Rod Bolt ?
Lance
THUS they are not built to "feel" a bolt stretch as can the Human Hand.
I ALSO state Rod Bolt Life is measured by length increase. (new/used)
WHO can state the difference between the Head Bolt/Rod Bolt ?
Lance
05-06-2018, 10:48 AM
#35
Stock or stock replacement (e.g. FelPro) head bolts are TTY, and one-time-use ONLY.
Think of them as being, rather than "bolts", calibrated SPRINGS. As "bolts", they are kinda too small, unless made of REAL HIGH tensile strength steel; they are designed to be tightened until they lose their perfect (or nearly so) dimensional properties, and instead operate in a range where they stretch a controlled amount to regulate the tension. ARP and the like may be designed to work more like traditional bolts, which behave more like a clamp than a spring.
Lance, I don't know what you're looking for on that. Although, most rod bolts these days are designed to be tightened until they stretch some specified amount; with some stock ones, the torque spec gives close enough to the right stretch, but with others, you have to use the method of tightening until "tight", whatever that might be for the particular bolts, then adding more torque to provide the correct stretch; or, actually directly measuring the stretch, since that also gives you the capability of comparing it on tear-down to what was recorded at build time, to diagnose end-of-life.
Rocker bolts in these motors, I see some people say they're TTY and others not. Personally I can't feature how a bolt THAT SMALL could thread into ALUMINUM and get tight enough to TTY. Especially since the torque spec on em is pretty much what you'd expect in normal usage for non-TTY bolts of that size. But I don't know that for sure so don't take what I say as gospel. The intake bolts (and valve cover ones for that matter... they work the same way) however, just squeeze some rubber, which then regulates the clamping force. All the bolt tightness does, is to lock it against something to hold it still from turning. That tubular thing it goes through is what it tightens against, not anything to do with the intake itself. I can't imagine how it would ever be worthwhile to re-torque any of those things.
Think of them as being, rather than "bolts", calibrated SPRINGS. As "bolts", they are kinda too small, unless made of REAL HIGH tensile strength steel; they are designed to be tightened until they lose their perfect (or nearly so) dimensional properties, and instead operate in a range where they stretch a controlled amount to regulate the tension. ARP and the like may be designed to work more like traditional bolts, which behave more like a clamp than a spring.
Lance, I don't know what you're looking for on that. Although, most rod bolts these days are designed to be tightened until they stretch some specified amount; with some stock ones, the torque spec gives close enough to the right stretch, but with others, you have to use the method of tightening until "tight", whatever that might be for the particular bolts, then adding more torque to provide the correct stretch; or, actually directly measuring the stretch, since that also gives you the capability of comparing it on tear-down to what was recorded at build time, to diagnose end-of-life.
Rocker bolts in these motors, I see some people say they're TTY and others not. Personally I can't feature how a bolt THAT SMALL could thread into ALUMINUM and get tight enough to TTY. Especially since the torque spec on em is pretty much what you'd expect in normal usage for non-TTY bolts of that size. But I don't know that for sure so don't take what I say as gospel. The intake bolts (and valve cover ones for that matter... they work the same way) however, just squeeze some rubber, which then regulates the clamping force. All the bolt tightness does, is to lock it against something to hold it still from turning. That tubular thing it goes through is what it tightens against, not anything to do with the intake itself. I can't imagine how it would ever be worthwhile to re-torque any of those things.
05-08-2018, 05:39 PM
#36
I know a few who reused the bolts without any problems. I personally would reuse them BUT the time it takes to clean them properly isn't worth it to me. One other thing you should never remove head bolts in these aluminum blocks without first relieving the threads with a sharp blow to the head of the bolt<this action causes the bolt threads to release from block threads. If you read GM's instructions on removing the bolts they want you to take a large flat punch and hammer then WHACK each head bolt before removal.
THAT IS ALL.
THAT IS ALL.
05-09-2018, 03:46 PM
#37
Head bolts are torque-to-yield and should never be reused while rod bolts are simply torque-angle. The rod bolts can be reused only if there is no neckdown. The late GM TTY head bolts are a great example of why TTY should not be reused as the stretch is quite visually obvious when removed from service, especially so when compared to a new bolt.
Manufacturers only use torque wrenches with book procedure when hand building. The machines they use on the assembly line torque all at the same time (ideal method) and actually do follow the torque angle procedure.
05-10-2018, 06:39 PM
#40
No they don't, I seen them being built. where did you see them being built? Person loads the bolts onto the engine and uses a large robotic air tool. All the bolts were tightened at same to a torque spec. No angle BS involved. All that angle BS is to fool you guys into ooowww AHHHHH I gotta jump how high?