mls gasket and stretch bolts

[AC sports]

Is it imperative to use stretch bolts or rather torque to yield angle bolts with a coated mls gasket?
Also can the bolts be re used? Cast iron block and alloy head application. Lots of different opinions I'm hearing. 11:1 comp. Hi po motor.

[peejay]

All bolts stretch, so for clarity I'll call them by what they really are: torque to yield.

MLS does not require torque to yield bolts. (And TTY bolts do not require MLS) I've done dozens without TTY, with stock bolts, ARP bolts, and ARP studs. One of my personal cars has ARP studs and MLS gasket with no problems.

A lot of torque to angle applications are not actually torque to yield. Torquing to an angle is like torquing rod bolts with a stretch gauge. Sicne you can't access both ends of the bolt to measure, you set the bolt to a minimum spec to get everything "set", and then a certain number of degrees WILL make a certain amount of stretch. If the thead is 1.0mm pitch and you torque the bolt 180 degrees, that is .5mm/.020" of stretch, because threads is threads. (Subaru head bolts are torque to angle but not TTY for example. At least, i have NEVER seen a yielded one)

Bolts that have yielded should not be reused. I've done it successfully, with a digital torque wrench simply for ease of use, but it was one of those "it's this or nothin'" deals and I'd rather not do it again. Pull the bolt up to the "set" torque, then pull through the torque angle OR when the torque stops increasing and then STOP.

Bolts that have a coating on them should NOT be reused at all. VW head bolts are like this. They are not TTY bolts, but they have a moly coating on them. The first time you use them, they turn like butter and it almost feels like they aren't doing anything. The second time, they crack and back and snap and fight you and you pull them out and throw them away and install new bolts like you should have in the first place.

[midnightbluS10]

All bolts stretch, so for clarity I'll call them by what they really are: torque to yield.

MLS does not require torque to yield bolts. (And TTY bolts do not require MLS) I've done dozens without TTY, with stock bolts, ARP bolts, and ARP studs. One of my personal cars has ARP studs and MLS gasket with no problems.

A lot of torque to angle applications are not actually torque to yield. Torquing to an angle is like torquing rod bolts with a stretch gauge. Sicne you can't access both ends of the bolt to measure, you set the bolt to a minimum spec to get everything "set", and then a certain number of degrees WILL make a certain amount of stretch. If the thead is 1.0mm pitch and you torque the bolt 180 degrees, that is .5mm/.020" of stretch, because threads is threads. (Subaru head bolts are torque to angle but not TTY for example. At least, i have NEVER seen a yielded one)

Bolts that have yielded should not be reused. I've done it successfully, with a digital torque wrench simply for ease of use, but it was one of those "it's this or nothin'" deals and I'd rather not do it again. Pull the bolt up to the "set" torque, then pull through the torque angle OR when the torque stops increasing and then STOP.

Bolts that have a coating on them should NOT be reused at all. VW head bolts are like this. They are not TTY bolts, but they have a moly coating on them. The first time you use them, they turn like butter and it almost feels like they aren't doing anything. The second time, they crack and back and snap and fight you and you pull them out and throw them away and install new bolts like you should have in the first place.

Engine Builder Mag has a decent article on TTY fasteners. Not sure how accurate the info is since it's from 2001.


I notice they talk about TTY and Torque-to-angle bolts. There seems to be a difference. What's all of your opinions on that? Is TTY and TTA the same thing? Different? What's the difference, in your opinion?


http://www.enginebuildermag.com/2001/02 ... -to-angle/


Went through 2 sets of head bolts on my Trailblazer. At $90/set, it wasn't something I enjoyed. It sucks throwing away bolts that were only installed 24 hours prior. At $90, I didn't want to chance it. That's cheap insurance to know my bolts weren't going to be an issue.

Personally, I won't ever reuse any bolts that are "torque-to-anything". Coating or not.

When a bolt comes under load, it exhibits four main phases: the elastic phase, the plastic phase, the yield point and the shear point. In the elastic phase, a bolt will stretch under tension but will return to its original condition when the load is removed. As we continue to apply the load the bolt reaches the plastic phase from which it cannot recover to its original length and is now permanently stretched. The point that separates between the elastic phase and the plastic phase is called the yield point. We have all experienced the plastic phase when a distinct softening of the load occurs. This is known as the oh moment that you know you are in trouble. To continue to apply the load, the shear point will be reached and the bolt breaks.

As with conventional bolts, torque to yield bolts are tightened in a series of stages and in sequence. Torque to yield bolts are generally tightened in sequence to what is known as a snug torque value. This snug value is to ensure that the component, in this case say a cylinder head is firmly located on the block. Correct sequence tightening is essential to eliminate distortion. Torque is further applied in sequence through a series of motions only this time instead of torque load being measured, angle of rotation is measured. The manufacturer will have specified what load is required and this specification could look as follows:

Tighten in stages and sequence to 40Nm
Tighten in sequence to 90degrees
Tighten in sequence a further 90 Degrees
Measuring rotation in degrees instead of an applied torque figure ensures that friction does not overcome the tightening process and that an even clamp load is easily achieved.

Different to conventional bolts, torque to yield head bolts are tightened beyond their elastic range, past their yield point: i.e. past the point from which the bolt material can recover to its original length: and into the plastic phase of the bolt material.

The bolt is permanently stretched and for this reason should not be reused. The reliability of these bolts once stretched is greatly reduced, if they are reused, they are permanently stretched further a second or third time. It is for this reason, you should never reuse a torque to yield bolt and always follow the manufacturers specifications.

For more information on the correct tools for Angular Torque – Torque to Yield please contact Warren and Brown about their Electronic Angular Torque Wrenches and Angular Torque Gauges.

TTA and TTY put the bolt well past the elastic stage. At that point, the bolt is done. It cannot be reused like a standard bolt thats torque to a set torque limit and never makes it past that elastic stage, where it returns to its original condition.

[peejay]

Good article, thanks for sharing!

I'll be sure to link that to the rotary guys who think it is okay to replace the factory 10mm bolts torqued to 23-29ft-lb with 1/2" studs torqued to 50 ft-lb.


As far as Trailblazers go... I haven't had to work on one of those yet, but I heard that their bolts are so "special" that they may break when installing. Lovely.

[midnightbluS10]

Yea, those sucked. I got lucky and didn't break any upon installation. But I also used ARP lube under the bolt heads, between the head bolt and washer. After replacing them once, I wasn't looking forward to replacing them again. They ended up revising the original bolts. They moved the yield point up the bolt so when they do break, it will leave some of the bolt above the deck, making them much easier to remove. The originals had it down low, right above the threads.


These look like the updated bolts. Notice the necked down portion up high on the bolt. The originals had it right above the threads.




VS old bolts




Removing them was hell, too. I broke 3. Most people break at least half of them. Usually more. I know of cases where guys broke 12 out of 14 of them. One stayed together with about 1/2 thread connecting the upper and lower pieces. I was able to spin it out by hand without breaking it entirely. The other 2 came out very easily with a pick to spin one out by hand and an ez out to get the last one. The good bolts creaked and cracked and moaned and groaned the entire time they were removed. The ones that broke were quiet from the very beginning. I could tell immediately which were going to come out and which were going to break.

Cleaned them out with the $50 thread cleaning tool from ARP and installed the new ones. Ended up replacing the new bolts after I put the head on the block and didn't tighten it down. It sat that way over the weekend and when I got back on it Monday morning, the cam lube I used had drained down the drain back holes and got between the block and head. I didn't realize it so when I torqued them down, red liquid(Permatex Ultra Slick lube) appeared at the head gasket. D'oh! So I pulled it apart, cleaned it all up, put a new gasket on and installed new bolts.


Its been running perfect for the last 7 months. Pulled it apart due to a burned valve on Cyl 1.

The machine shop almost screwed me on this deal. Luckily, I'm experienced enough to know to check everything.

They had tightened the cam bearing caps down so much, the cam would hardly turn. Spec was something like 100 in.lbs.

I think they used 100 FOOT lbs. Thankfully I found it before installation.

The shop was Mills Motors in Shreveport, LA. I'm sure Joe Carroll knows of them.

[Krooser]

I repaired a 4.3 Chevy several years ago in my son's Blazer... Spun rod bearing.

When getting the parts at the local parts house I asked about tty head bolts... Their book said " do not reuse more than once".

Didn't buy bolts...never had a problem with the engine.

[peejay]

TTA does NOT always mean the bolts go past the elastic stage! It just means they want a more specific tightening specification than a torque reading, which is highly dependent on thread condition and cleanliness/lubrication.

The automakers are specifying TTA for a LOT of things nowadays, not all of them critical fasteners or deliberately undersized fasteners. I've seen TTA called out for bellhousing bolts, caliper bolts, etc.

TTA is just a way of measuring bolt stretch without the ability to access both sides of the bolt. 90% of rod bolts are not torque to yield but they get torqued with a stretch gauge because it is more accurate than using a torque wrench, and you can actually access both ends. If you couldn't access both ends, the spec would be something like setting the rod nut down to 15 ft-lb to seat everything, then 90 degrees to get the amount of stretch desired. It isn't necessarily yielding.

Hell. Talking again about rotaries. The torque spec for the flywheel nut is 290-360ft-lb. Since reasonably inexpensive torque wrenches stop at 250ft-lb, people have worked out that you can get the proper torque by torquing to 150ft-lb and then going another 60 degrees. Does that mean that the end of the shaft is yielding? No, it just means it is a different way of quantifying the proper load on the fastener.

[Newold1]

It sounds like you are building the engine from scratch. If that's the case, KEEP IT SIMPLE! and buy a nice set of ARP head bolts or studs(better) and install them following ARP's instructions for LS engines and put another issue on the BUS! Don't over think this!

[midnightbluS10]

I repaired a 4.3 Chevy several years ago in my son's Blazer... Spun rod bearing.

When getting the parts at the local parts house I asked about tty head bolts... Their book said " do not reuse more than once".

Didn't buy bolts...never had a problem with the engine.

The 4.3V6 uses standard bolts like a sbc. The 4.2L I6 doesn't.

[user-23911]

If you take time to read a few service manuals, you'll learn a bit.


There's at least 2 different ways to tighten bolts, it's got nothing to do with whether the bolts are TTY or not.

TTY bolts are torque to yield, not torque past yield.

Several Mitsubishi engines use TTY bolts, probably the most common / popular being the 4G63.

Google will tell you that you can't reuse the bolts.
That's because most of what you find from google comes from a flock of sheep who don't read manuals............or salesmen who sponsor ricer forums.


When you read the manual it tells you the length of bolt and it says that it's OK to reuse them so long as the length is within spec.
If it's put together properly , the bolts return to the correct length.

The likes of the LS, the manual says not to reuse them but applying the same logic, you CAN.



If you're not willing to experiment you'll never learn anything and you'll be living in the dark ages for ever AND you'll be short of money.
Don't listen to salesmen, they just want to sell more un needed parts.

[pdq67]

Gen I SBC engine here!

I wire brush clean my old bolts and chase their holes and use brake clean and blow them clean/dry.

Then I coat their threads with good old Indianhead along with a bit under their heads.

Then I carefully usually use my old beam torque wrench by torqueing them from say 25 pound starting out on up in two more pulls. I have a cheap click wrench but really don't trust it all that much.....

Then run my engine through a couple of hot/cold cycles and check their torque each time..

Always been good to go.

A couple of other things here that I also do.

I take a small fine bastard cut triangle file and WD-40 and carefully go from bolt-hole to bolt-hole on both the head and block decks watching the crud come off and the decks shine up as they smooth out. THIS IS A FEELIE DEAL so don't get carried away.

Then I coat the decks and both sides of my head gaskets with Indianhead and let it tack up and assemble. Torque as above!

pdq67

[woody b]

Trailblazers were mentioned. To keep the bolts from breaking when you're removing them give them a good whack on the head. I use a 3 pound hammer and a punch. This helps break them loose and keeps them from breaking. I've done a bunch of Trailblazer heads. The only ones I've had break when removing was the ones under the cowl. I couldn't get a good wack on them. I've never had any break during installation. The only ones I've seen break during installation were ones where the bolt holes weren't clean. When they break (during removal or installation) they usually break below the deck surface. GM has a special tool that's a drill guide. It fits in the hole to center the drill bit. Most times a left had bit will bring the broken bolts right out.

[Krooser]

I've found that a good soak with a quality penetrating oil helps... but you need at least 24 hours and enough ambition to spray the elixir on the bolts several times.

[Krooser]

I repaired a 4.3 Chevy several years ago in my son's Blazer... Spun rod bearing.

When getting the parts at the local parts house I asked about tty head bolts... Their book said " do not reuse more than once".

Didn't buy bolts...never had a problem with the engine.

The 4.3V6 uses standard bolts like a sbc. The 4.2L I6 doesn't.

The one we had used TTY... not sure why but they were even listed in the book. Was a head scratcher for us, too.