Head studs, stripped threads, etc - Land Rover Forums : Land Rover and Range Rover Forum
 1Likes
  • 1 Post By p76rangie
 
LinkBack Thread Tools Display Modes
post #1 of 11 (permalink) Old 04-01-2017, 06:34 PM Thread Starter
Ian Matthews
 
p76rangie's Avatar
 
Join Date: Jan 2006
Location: Melbourne Australia
Posts: 5,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 151 Post(s)
Head studs, stripped threads, etc

I attempt to share my failures so that others do not make the same mistakes.

This one relates to using ARP head studs instead of the standard head bolts.

For decades now I have used ARP head studs on Rover V8's rather than the standard head bolts. I believe there are many advantages of head studs like more consistent pressure, reusability, etc.

I have never had to replace a head gasket where I have used studs due to them holding down the head better.

However, I had to pull the head off my wife's disco a little while ago due to coolant getting into the middle two cylinders. It wasn't a bad leak, but it was enough to cause the plugs to rust and fowl about every 5,000 miles. So I pulled the heads off to have a look.

Could find any reason for the leak, so I just decided to put them back on.

When looking at the old head gaskets, I noticed that they were very compressed around where the head studs were. This lead me to look at how tightly the studs pull down the head compared to bolts. Basically the studs are a 7/16 20 thread of hardened steel with hardened steel washers. The standard bolts are a 7/16 14 thread with harden steel bolts being screwed into a alloy block. Looking at various articles, nearly 90% of the torque you apply to a bolts is used up in the friction of the thread and the friction to the washer. Therefore apply the same torque to a head bolt with a 14 pitch thread into alloy is going to supply a lot less clamping force (compression on the gasket) than a 20 pitch thread of hardened steel to hardened steel.

The stud tightened to the same torque as a bolt is also going to place a lot more stress on the threads cut into the alloy block of the motor.

It is not uncommon to rip the threads out of the block when tightening an ARP stud to the recommended torque.

There are complicated formulas to work out what the different torques should be, but they were well over my head to figure out.

A steel to steel thread lubricated at 55 ft/lb applies 9,500 lb of clamping force for a 14 pitch thread and 10,500 for a 20 pitch thread. Alloy to alloy lubricated has twice the resistance than steel to steel lubricated.

The difference friction makes. A steel 7/16 20 thread unlubricated only provides a clamping force of 7,500 lb at 55 ft/lb where by simply lubricating the same thread the clamping force increases to 10,500 lb for 55ft/lb

So when refitting the head I simply backed the torque off from 65 ft/lb (recommended) to 55 ft/lb.

However, I still managed to strip one stud out of the block when refitting the head.

So I drilled out the thread and fitted a Helicoil. Everything seemed to tighten up properly and I never gave another thought to it.

Last week the motor blew the head gasket right out the side of the head, the motor made a hell of a racket like a bad exhaust leak.

So off came the heads again. I found that the helcoil had pulled up the block around the thread allowing the head gasket to come loose around that area, first blowing between the cylinders and the to the outside of the block.

I thought that the helical had simply been fitted to close to the top of the block. So pulled it out and fitted a new helicoil deeper down.

Went to refit the head and managed to pull the helicoil out at only 50 ft/lb.

It ends up that the old helicoil sitting so high in the block meant that it was actually the head stopping it from stripping out. That is it was the head holding it down.

So now I have a big bolt hole in the block. That is, the old thread was drilled out to fit the helicoil thread, which has now stripped out as well. So I can't fit another helicoil, so at a loss what to do.

Now I have found these other inserts, they go under a number of trade names, two such names are Keensert and Keysert. They are a bit harder to find and I will have to wait till Monday to find a supplier.

I will let you know how I go with them.

The two main advantages with them over Helicoils are that Helicoils require a specialised tap to put the thread in. These are VERY expensive. The Kerserts and Keenserts only require a standard tap to fit them. The Keyserts and Keenserts are one solid unit rather than a spring like device and are therefore much stronger. However, the inserts are a lot more expensive that the helicoil type units. They are around 5 times the price.
p76rangie is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old 04-01-2017, 07:21 PM
Wounded Knee Moderator
 
ihscouts's Avatar
 
Join Date: Dec 2008
Location: Traverse City MI
Posts: 1,882
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 86 Post(s)
I've never had it happen personally but these or something like them are more what hyperf engine builders use with an alloy block; ++ TIME-SERT Official Threaded inserts for stripped threads, blown out sparkplugs,

When I read your post I was immediately bummed.........

97 SD - Altai Silver. Sold
94 Saturn SC2

Roverless and wandering

The three-position Lucas switch--DIM, FLICKER and OFF.

The other three switch settings--SMOKE, SMOLDER and IGNITE.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


Ultragauge
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


Contact info for Paul Grant;

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

203-770-1699

Contact info for Will Tillery;

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

540-462-7353
ihscouts is offline  
post #3 of 11 (permalink) Old 04-01-2017, 10:22 PM Thread Starter
Ian Matthews
 
p76rangie's Avatar
 
Join Date: Jan 2006
Location: Melbourne Australia
Posts: 5,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 151 Post(s)
Quote:
Originally Posted by ihscouts View Post
I've never had it happen personally but these or something like them are more what hyperf engine builders use with an alloy block; ++ TIME-SERT Official Threaded inserts for stripped threads, blown out sparkplugs,

When I read your post I was immediately bummed.........
I looked at the timeserts, but with the flange on the top you can't double them up for extra length. I am determined not to have it strip out again, so I am going to put two in, one on top of the other for extra thread depth.
p76rangie is offline  
 
post #4 of 11 (permalink) Old 04-02-2017, 06:15 AM
Wounded Knee Moderator
 
ihscouts's Avatar
 
Join Date: Dec 2008
Location: Traverse City MI
Posts: 1,882
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 86 Post(s)
The ones for head bolts are longer without the flange......
Attached Thumbnails
Click image for larger version

Name:	TS10129.jpg
Views:	24
Size:	34.3 KB
ID:	76170  

97 SD - Altai Silver. Sold
94 Saturn SC2

Roverless and wandering

The three-position Lucas switch--DIM, FLICKER and OFF.

The other three switch settings--SMOKE, SMOLDER and IGNITE.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


Ultragauge
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


Contact info for Paul Grant;

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

203-770-1699

Contact info for Will Tillery;

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

540-462-7353
ihscouts is offline  
post #5 of 11 (permalink) Old 04-02-2017, 06:23 AM
Senior Member
 
Join Date: Mar 2016
Posts: 848
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 244 Post(s)
Helicoil makes a head bolt specific insert which has a length three times diameter, which is the proper rule-of-thumb engagement depth for aluminum. Even so, it's impossible to bore a root diameter hole accurately with a hand drill, so about the best class of fit you can expect to get is 1B. A precision hole (one that would see high torques) is going to be 3B. You lose close to a third of your holding strength in that jump. Best case, a Helicoil is a "maybe it works..." proposition. It's a good job saver for things like spark plug holes, but it's not a high-precision, high-strength product. You'd have a much better chance at success with the Timesert, but I've seen those fail as well. As always, it may have had more to do with the person doing the repair than the product.

On the ARP studs, when I did my first Rover, I, as many others have, questioned the torque spec at 90 ft/lbs. I did the math and came up with 72 Ft/lbs, based on the 7/16-14 thread and 180Kpsi material used in their studs. I called ARP and spoke to one of their engineers, who couldn't explain the 90Ft/Lb spec. We traded some emails back and forth on the issue. He did mention that he felt that their 8740 studs in this application were closer to 185K, so I set the torque at 75 Ft/lbs and called it a day. In December, ARP replaced their spec sheet for the Rover kit with an amended torque spec at 70.

Bolt torque isn't some arbitrary number. A precision, torqued fastener is essentially a spring. It needs to be torqued to a specified point in the elasticity range of the material to ensure stable, lasting clamping force through all the operational range of the fastener. If you're not going to torque them to the proper spec, you can save a bunch of money and buy a couple sticks of all-thread and make your own. If the block won't hold the torque, it's a defective block and destined to fail, either by pulled thread or failed gasket.

I discovered that from the factory, the Rover head bolt holes are cut with a plug tap. That means that, at the bottom, the threads are cut at a decreasing rate (kind of like a pipe thread). The holes are a little deeper than the TTY bolt is long, so it doesn't matter. But the stud should be able to bottom in the hole and not bind the thread. If it binds, it can cause an expanding force in an already over-stressed area, especially on the deck's end holes. To alleviate the problem, you should cut that last little bit with a bottoming tap, preferably a class 3B, to get a good thread.
CT090 is offline  
post #6 of 11 (permalink) Old 04-02-2017, 09:32 PM Thread Starter
Ian Matthews
 
p76rangie's Avatar
 
Join Date: Jan 2006
Location: Melbourne Australia
Posts: 5,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 151 Post(s)
Trying to find the inserts stocked by anyone was the hard part. Had to follow hint from one outlet to another and then to another. I ended up using a Timesert. Actually it was their bigger version called a Bigsert. Found a very good supplier, he even lent be the tools to put it in. The Bigsert was exactly the same length as the thread on the stud and therefore worked out perfect.

Some nerve racking moments as you drill out the block with a 37/64 drill bit (which was also hard to find) and making sure you keep it at the right angles, etc.. I wish I was a drinking man as a few shots before hand may have made it easier. Even though Timesert keep the type of tap used a secret, for these units it is a 16mm 1.5 tap if you do not wish to pay the relatively high price for their kits.

The head is now on and tensioned down to 60 ft/lb. Anyone that goes by the ARP listed tensions is mad. I certainly would not go past the Land Rover torque specs. Land Rover make the block and know how much stress it can take. Before the went to TTY bolts, they set the torque at 65 to 70ft/lb for normal head bolts and that is with the courser 14 pitch thread onto an aluminium block. I know that 65 ft/lb on the ARP studs is too much as it completely flattens the head gasket around where the studs are. As it does not flatten all the gasket it must mean that they are applying so much pressure that they are actually distorting the head. So I am more than happy with the 60 ft/lb I was game enough to get them to.

The thing to note with the standard Timeserts is that they use the same hole (29/64)and thread as Helicoils, yet they are a one piece unit. The Bigsert uses a much bigger hole at 37/64ths

Last edited by p76rangie; 04-02-2017 at 10:59 PM.
p76rangie is offline  
post #7 of 11 (permalink) Old 04-03-2017, 04:04 AM
Member
 
Join Date: Mar 2017
Location: Victoria Au
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
G`day ,


If it`s a V8 which it sounds like when you pull the head off next have a close look at the top of the middle 2 liners and deck surface , scrap across with you finger nails and feel for a catch .

Compare what you see and feel with the two outside cylinders .

If coolant is found in the end cylinders it can be leaking past the head gasket .

If coolant is found in either of the 2 middle cylinders it is very likely to be a crack in the block and the coolant if found in the cylinders has leaked between the liner and block but has come from a crack in the block behind the liner .

If you look at the old head gaskets there are coolant holes on each end but nothing in the middle , other than the ends the coolant is enclosed inside both the block and heads .
peter r is offline  
post #8 of 11 (permalink) Old 04-03-2017, 04:29 AM
Wounded Knee Moderator
 
ihscouts's Avatar
 
Join Date: Dec 2008
Location: Traverse City MI
Posts: 1,882
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 86 Post(s)
Glad you where able to resolve this so quickly, not bad at all!

97 SD - Altai Silver. Sold
94 Saturn SC2

Roverless and wandering

The three-position Lucas switch--DIM, FLICKER and OFF.

The other three switch settings--SMOKE, SMOLDER and IGNITE.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


Ultragauge
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


Contact info for Paul Grant;

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

203-770-1699

Contact info for Will Tillery;

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

540-462-7353
ihscouts is offline  
post #9 of 11 (permalink) Old 04-03-2017, 05:27 AM Thread Starter
Ian Matthews
 
p76rangie's Avatar
 
Join Date: Jan 2006
Location: Melbourne Australia
Posts: 5,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 151 Post(s)
Quote:
Originally Posted by peter r View Post
G`day ,


If it`s a V8 which it sounds like when you pull the head off next have a close look at the top of the middle 2 liners and deck surface , scrap across with you finger nails and feel for a catch .

Compare what you see and feel with the two outside cylinders .

If coolant is found in the end cylinders it can be leaking past the head gasket .

If coolant is found in either of the 2 middle cylinders it is very likely to be a crack in the block and the coolant if found in the cylinders has leaked between the liner and block but has come from a crack in the block behind the liner .

If you look at the old head gaskets there are coolant holes on each end but nothing in the middle , other than the ends the coolant is enclosed inside both the block and heads .
Have done all that. I had a block once that had 4 slipped liners in it.
I had a expert in Land Rovers look at it as well. It is not coming from the block. Most likely from the head, so I have changed the head. There is a very slight chance that it might have been the intake manifold, so I am changing that as well.
The odd thing was that there was enough moisture getting in to rust the plugs and the surface of the exhaust valves, but not enough to clean the carbon off the tops of the pistons or the combustion chamber. It was a very odd case.
p76rangie is offline  
post #10 of 11 (permalink) Old 04-03-2017, 06:27 AM
Member
 
Join Date: Mar 2017
Location: Victoria Au
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Yes , that sounds a bit different , they are usually pretty predictable .

I have know of heads that have been modified, ports opened that will crack were the head bolt passes through but usually std heads don`t crack that i`ve heard of .

If you`ve only had one your doing well , in the shed i have a 3.5 a 3.9 and 4.0 all with 1 liner that`s moved .
The 4.0 was a fluid problem but the 3.5 and 3.9 were just noisy .

I`ve used , not helicoil but recoil brand with success on head bolts , i know the taps are a special inbetween size .

I`m happy using the old type reusable bolts , i`ve always though the yield bolts were unkind to the block , i don`t use studs because of the price nowdays .

PLR elsewhere

84/5 RR 4.0ltr Torqueflite Standard

93/4 RR 3.9ltr ZF Hard dash Vouge SE

94/5 RR 4.6ltr ZF Soft Dash Vouge SE

03/4 RR 3.0ltr TD6 GM HSE
peter r is offline  
post #11 of 11 (permalink) Old 04-03-2017, 05:23 PM Thread Starter
Ian Matthews
 
p76rangie's Avatar
 
Join Date: Jan 2006
Location: Melbourne Australia
Posts: 5,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 151 Post(s)
This is not related to threads, but it relates to heads.

In case you are not aware, the rocker shaft assemblies are not interchangeable between the sides of the motor unless you strip them down and reverse the rocker positions.

The holes that allow oil to the rockers are offset on the shafts due to the angles that they are bolted down at. If you put them on the wrong side the oil holes will not be in the correct positions on the shafts and will not lubricate properly.

As I just changed over the head on the disco I stripped down the rocker assembly for a bit of a clean and found that it had been assembled wrong.

There is a notch in one end of the rocker shaft. This notch needs to be at the top of the assembly. For you people that drive on the wrong side of the road, the notch should be at the front of the assembly on the passengers side and at the rear on the drivers side.
redtruck12 likes this.
p76rangie is offline  
Sponsored Links
Advertisement
 
Reply

  Land Rover Forums : Land Rover and Range Rover Forum > Land Rovers Only General Forums > General Land Rover Discussion

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Land Rover Forums : Land Rover and Range Rover Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Head studs MRussell Discovery Series II 1 04-23-2014 07:49 AM
Stripped head bolts jamesimm02 Discovery Series II 3 05-19-2013 08:31 PM
Head Studs bflener Discovery Series II 9 04-14-2013 03:52 PM
Oil cooler line replacement leads to stripped threads....Help! luvboates Discovery Series II 2 02-10-2010 10:52 PM
stripped head bolt Burncycle Discovery Series II 74 01-07-2010 09:00 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome