SmaknaSS

iTrader: (1)

I was reinstalling my heads using the JMX method when on the last step I was suposed to torque bolts 9 & 10 to 50 degrees but instead I accidently torque them to 135 degrees! My question is should I buy a new set of torque to yeald bolts and start over again? or should I just back off the bolts 9 & 10 that were over torqued? What should I do? thanx in advance.

jmX

From my website:
"torque all 10 15mm bolts to 22lb-ft."
...
"turn all 10 15mm bolts an additional 90 degrees"
...
"turn bolts 1 through 8 another 90 degrees"
...
"turn bolts 9 and 10 an additional 50 degrees."

Is that what you did? It sounds like its what you did, and if so, thats what you were supposed to do!

It results in bolt 1-8 being turned 180 degrees total, and bolts 9 and 10 being turned 135-140'ish degrees total.

robertbartsch

Wow! When I did my heads I sprayed the bolts with a light coat of silicone.

Then I tried to follow the JMX method of torking using a felt tip marker. Unfortunately, the silicone prevented me from marking the head bolts; nothing worked....

I ended up torking the bolts in three-stage increments to a total of 75lbs for the long bolts and slightly less for the 4 short bolts... Apparently, this is the correct spec.

Just to make sure, you might check your final torque numbers against a tork wrench set at 75lbs...

If they are over-torked, I do not recommend lossening the bolts since the gasket will probably not seal... just leave them as is or rip it apart and start from scratch...

Some believe the tork-to-yield bolt thing is bull and I have had a few discussions with a GM dealer who NEVER uses new bolts and another engineer who says all bolts stretch and not to worry...

I my rig I used new bolts, but I think it is not neccessary...the GM dealler has had no problem for many years re-using the old bolts...

..Head gaskets are another story, they cannot be reused.

robertbartsch

I thought under the JMX method all the lines you drew across the head bolts were re-alinged after the proper torking....

If this is correct, you should be able to tell if you turned the bolts the correct amount.

If yes, it would be interesting to know, the tork spec that it yields?

Can you please measure the tork for the long and short bolts and post the results, here. It would be intersting to know how it compares to the published tork specs....

Thanks...

MYBLKSS

iTrader: (1)

Dude I wouldn't worry about it as long as both (9,10)are equall (135*). I did the same thing on my car and everything is still together after 4 dyno pulls and about 1000 miles, but if it makes you feel better pull it back apart.

SmaknaSS

iTrader: (1)

What I was trying to say is that on the 2 nd to the last step when your suppost to torque only bolts 9 & 10 to 50 deg I went instead to 135 deg for a total of 225 deg , maybe I can try to find the total torque for those bolts but I want to make absoulty sure first. thanx for all the replies folks, please keep them coming!

robertbartsch

...So you torked the head bolts out of sequence, right?

...definately not a good thing, but I would not worry too much...since you have not heat-cycled the motor yet your probably OK....

I would go over each bolt (long and short) with a tork wrench and see if they are close to 75lbs...a little less on the shorter bolts...

J-Rod

Torque-To-Yield Cylinder Head Bolts

Also referred to as "angle torque" or "stretch bolts" Originally unique to import nameplates, this type of head bolt was introduced on North American engines in the mid-1980's . Today all import and domestic engine manufacturers use TTY head bolts.


What is Torque-To-Yield?

All bolts stretch when tightened. When stretched, a bolt tries to return to its original length, much like a spring. It is this elastic quality that provides the clamping force necessary to seal a gasket properly. When a bolt is stretched to the point it can no longer return to its original length, it is permanently distorted and has reached its yield point. After a bolt has yielded, it can no longer provide its full clamping force.

Why do Manufacturers use Torque-To-Yield?

Engine designers prefer the use of TTY bolts for several reasons; TTY bolts:

Provide more uniform and accurate clamping force on the head gasket, resulting in improved engine performance and reliability.
Deliver 100% of their strength, by comparison conventional bolts only use about 75% of their strength.
Prevent over-tightening of the head gasket.
Generally eliminate the need to re-torque after a break-in period.
Eliminate the inconsistent clamping forces created by the friction-tightening method.
Can Torque-To-Yield bolts be re-used?

Most engine manufacturers require new TTY bolts be installed whenever head bolts are removed. A few do provide guidelines on re-use of the original bolts. The problem with re-use is there is no accurate visual method of determining their condition, and most repair facilities do not have the capability of accurately testing them. Cylinder head bolts provide the clamping force necessary for the head gasket to properly seal and function. Uneven or improper clamping force will cause a head gasket to fail prematurely.

It is recommended to replace TTY bolts whenever they are removed.


How to Identify an Engine with Torque-To-Yield Head Bolts

Early TTY bolts were easy to identify by their undercut shank. Since then, many new TTY designs have been employed. Many of these do not use an undercut shank and therefore cannot be easily recognized as TTY. The most accurate method of determining a TTY engine is based on the head bolt tightening procedure outlined by the manufacturer. If the installation procedure requires tightening the bolt to an angle (vs. torque) specification, the engine requires new TTY head bolts.


So, yes, a dealer can re-use TTY bolts, but there is a much greater chance that for instance on a set of heads, if you re-use a TTY bolt that the heads gasket will blow as in most cases your bolts are now no longer usable but are being re-used. Any dealership technician who re-uses TTY bolts when there is no defined procedure for doing so is negligent and careless in his work.

I spend a lot of time in a automotive machine shop. I have buckets of TTY fastentrs that get thrown away all the time. Very simply put you are simply asking for trouble if you don't buy new bolts.

robertbartsch

J-Rod:
OK I give up!!!! ...You will notice that I did not recommend re-using the old bolts ...I used new bolts with my new heads,,,,I just said re-using bolts has been done before with success.

Anyway, perhaps you could offer some advice here. When you tork out-of-sequence what should you do?

Would you:

1. rip it apart and start over with a new head gasket and new bolts

2. Let it go and hope for the best.

3. Check all the bolts for uniform torque??

Vents

iTrader: (9)

good info j-rod,

re-using the old bolts is asking for trouble. if we all had iron blocks and studs, this wouldnt be a problem. however, we dont. tty bolts are gay end of story.

what you can do is follow the pattern, and after the 22lb pass, i go 85 on the long "inner" bolts and 70 on the 2 stubby outsiders. it's the same ft LB rating as is used w/ the degree method on my tq wrench. might check it yourself first though. oh, and dont forget those top 5 bolts ;D

if you did it out of sequence, you can do one of 2 things. lazy option one, leave it and hope for the best (if you're n/a it could be considered)

not so lazy and not so cheap pain in the butt option 2, get new bolts/gaskets and take the time to do it over.

it's really just up to you. depending on how bad the "out of sequence" or degree's out it went, really determines whether or not it's going to let the gasket loose. if it's bad in your opinion, just take the time to do it right, since you have it apart now. gaskets are 12 bucks from napa, and bolts are about the same. i can get both for you if you need. i work @ a GM dealer.

SmaknaSS

iTrader: (1)

I did not torque the bolts out of sequece, I just over torqued the bolts 9 & 10 during the 4th step when you are suppost to torque 9 & 10 an additional 50 deg. I was thinking of documenting the amount of torque it takes to turn bolt 9 & 10 an additonal 50 deg when I install the the 2nd head then making the first head(the one that I over torqued) the same. any idea's?

robertbartsch

Well it would be very good to document this tork so people would know...

I assume bolts 9 and 10 are the two sort ones that have threads up to the top of the head...

It would also be intersting to know if the JMX method produces tork loads that are consistent with the published specs...

jmX

Guys, the "jmX" method is straight out of the GM manual. This is the GM method for doing things, the only difference is I mark a line on the head bolt to help count angles rather than making you go out and buy a torque angle meter wrench.

Go read the GM manual and its going to read exactly like what is on my website.

As for turning 9 and 10 225 degrees, thats INSANE!#@ I'd be afraid of the bolt breaking at this point, so what I'd do if I were you would be to either drive the car until you can replace #9 and 10 and do it then (which means you'll be retorqing them out of order, but since they are the outside bolts its probably fine), or just leave it and hope the head doesnt distort any and the gasket isnt too smashed. There is no standard protocol on what to do in this situation, but I dont think its THAT big of a deal...I'm just amazed the bolt didn't break.

Its definitly not a perfect solution, but its cheap and it'll *probably* get you by just fine. GM would probably say remove the head, put a new gasket, and replace all the bolts again but that is a bit extreme for your case IMO.

2001CamaroGuy

iTrader: (6)

this is one of the many reasons I ditched the torque to yield bolts and went with ARP 12point studs. I didn't have to play with all that "turn 50 degrees" BS....just look on the ARP box...read the spec (ex. 45 ft/lbs)...and torque.....

robertbartsch

Good point!

..do the other side EXACTLY according to the JMX directions and then measure the tork on each of the bolts recording them on a separate piece of paper....

Then go to the side you torked too much and test the tork specs against the other "good" side....


DO NOT LOOSEN ANY BOLTS ON THE BAD SIDE. If the tork differs by a bunch do this:

1. leave it and hope for the best, or

2. rip off the head from the bad side, replace the gaskets and bolts and start fresh!

robertbartsch

JMX:
Since your web page is legendary among our group, we tagged your head torking method as "the JMX method" (I was devestated when I recently learned you had not built any short blocks, however. I'm shocked and dismayed)

I dont think it is a good idea to drive the car, and then replace the two short bolts later...I would say that would surely lead to premature head gasket failure...

...I think if you loosen, or take off, any bolts you "loose" the head gasket and must take the head off and start fresh with a new gasket and new bolts...I don;t think the over torking will impact the head, right?

I also think if you over torked the bolt and it did not break then, chances are, it will not break later...It kinda proves my point that bolts are really over engineered and tork-to-yield bolts are ...well you get my drift....

I would LOVE to know the tork setting of the over-torked short bolts bolts compared to the JMX method...

Guys - any thoughts on this one...

Visceral

iTrader: (1)

Im thinking of about 5 or 6 other non-car related things that Im gonna call the jmX method



chris

Visceral

iTrader: (1)

He hasnt had time for that kind of trivial pursuit

chris
(practicing the Visceral Method)

trackbird

iTrader: (4)

One concern about potentially over torqued TTY bolts....These heads are aluminum and will expand (considerably more than iron heads) with heat. The extra stretch on the bolt over many fatigue cycles may cause a problem down the road. I'm not saying that it will, but it is something to consider as well. I would try to establish how much torque is on those bolts and if it exceeds the "recommended" amount by more than 10%, I'd pull it apart. These are just my thoughts....good luck!

Visceral

iTrader: (1)

After 4 or 5 head swaps, you get really tired of TTY bolts...