Author Topic: Why do I want "expensive" head studs for a 1.5 or early 1.6??  (Read 24723 times)

November 03, 2009, 09:33:38 pm

maxfax

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Why do I want "expensive" head studs for a 1.5 or early 1.6??
« on: November 03, 2009, 09:33:38 pm »
So it’s been asked dozens of times, “Why do I need to buy these expensive head studs for my 1.5L or early 1.6L?”  

The 1.5L  diesel (engine code CK)  and the 1.6L diesel (engine code CR) as used in  MK1 VW’s from 1975 till 1981 (sometimes early ’82) used 11mm head bolts (can be identified by an allen head).. These bolts only thread into the block approximately one half of an inch (or 12.7mm for you metric people) at best..   Since such a small amount of the block is used to hold the head on an engine making 400psi (27.6 bar) of compression and up there simply is not enough surface area to properly hold the bolt in place and maintain a proper seal..   Additionally since such a small area is utilized to hold such a large amount of force, this can cause the engine block to crack around the head bolt holes..  

Most commonly the holes crack when tightening the head down after replacing the head gasket..  Generally the most common holes to crack on these blocks are the ones on the four corners of the block, and the second hole in from the left of the car towards the front (the hole in which the oil is fed to the head). Although it is not impossible for any of the other holes to crack as well.

Some have tried to use the bolts used for the gas engines as they are a stretch bolt (can be identified by a triple square head but 11mm threads).  Some have used this with success, but the bolts themselves are not as strong as the original diesel head bolts or the studs..  They'll generally continue to stretch and the head gasket will leak again..

Some have discussed drilling and tapping the block and head to accept the later 12mm bolts. However after the drilling and tapping you’ll have even less metal in the block weakening it and once again cause the holes to crack…

The best and IMHO only solution for this issue at this point is to install either ARP or Race ware head studs.   Race Ware specifically makes studs for this application, ARP makes studs for the 8-valve gas engine that work fine on the diesel.   The ARP studs are generally half the cost of Race ware studs and are more commonly used. The ARP stud part number is ARP # 204-4701.  TO date the best bargain to be found for these is from Summit Racing.  

When installing the head studs first and foremost is to inspect your block for existing cracks around the head bolt holes.  IF there are cracks your block is junk.  I’ve tried several methods to repair this and at this point have had no success.   The next thing is to properly clean your threads in the bolt holes.   Chase a tap in the holes (If you do not have a tap, a slot ground in an old head bolt will work for this). After tapping spray some brake cleaner, or cab cleaner into the holes and then blow them out with compressed air.  

On MK1 VW’s it is not possible to install the studs before the head with the manifolds attached to the head.  One either has to install the manifolds after installing the head, or place the head and the gasket on the block and screw the head studs in.  Guide pins can be fabricated from old bolts to aid in this method.

Cut two old head bolts approximately 1” (25.4mm) above the threads.  Grind a slot into the bolt so that you can use a flat head screwdriver to turn them.   Install these pins into 2 of the end holes on the cylinder block.

After installing your pins lay the head gasket (proper side up) and the head on the block.   Screw the studs into the block (with nothing on the threads) by hand.  The ARP studs have an allen head to aid with installation, however the studs to not need to be more than snug in the block. After installing the studs install the washers and the molly grease provided onto the threads and torque to the spec provided by the manufacturer…

With the head studs you will drastically reduce head gasket failures, and virtually eliminate damaging the engine block.  And which is more expensive, a set of head studs or swapping in another engine block???

« Last Edit: December 15, 2009, 11:10:50 pm by maxfax »



Reply #1November 03, 2009, 11:20:01 pm

Vincent Waldon

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Re: Why do I want "expensive" head studs for a 1.5 or early 1.6??
« Reply #1 on: November 03, 2009, 11:20:01 pm »
Excellent FAQ and answer... thanks for posting!
Vince

Edmonton, Alberta, Canada
2001 silver TDI Jetta Malone Stage 1.5 , 2001 blue TDI Jetta SBIII 216s Malone Stage 3, 1970 Bay Window bus

Gone but not forgotten: 1969/1971 Beetles, 1969/1974 Westies, 1979 Rabbit, 1986 TD Jetta, 1992 gas Jetta, 1994 TD Jetta

Reply #2November 04, 2009, 12:12:43 am

maxfax

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Re: Why do I want "expensive" head studs for a 1.5 or early 1.6??
« Reply #2 on: November 04, 2009, 12:12:43 am »
Thankyou Vince..  I figured for as many times as I have give the 11mm speech it was time to put it up here..   AS I get some stuff rounded up I hope to add some pictures of what I am talking about...

If anyone woudl happen to have a pic of a cracked 11mm block or a gasser head bolt I would be grateful if you could throw that up on here..   After all of the these things I've had over the years the only cracked 11mm block I have left is the one in my daily driver...

Here are pics of a Diesel 11mm Head Bolt, The home made thread cleaner, and the guide pins



Reply #3December 27, 2009, 09:11:46 am

teftdossy

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Why do I want "expensive" head studs for a 1 5 or early 1 6
« Reply #3 on: December 27, 2009, 09:11:46 am »
I tried water but it didnt keep them in place....wats the best for making them stay in place without using that special glue?

thanks

Reply #4December 29, 2009, 10:18:36 am

truckoSaurus08

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Re: Why do I want "expensive" head studs for a 1.5 or early 1.6??
« Reply #4 on: December 29, 2009, 10:18:36 am »
Aww crap!  I just found out I have 11 mm head bolts. >:( Took the valve cover off my 81 1.6 caddy and those allen head bolts were there sure enough.
Would you recomend replacing the bolts one at a time even if the head gasket is good? Or maybe pull the head to check the block for cracks? Is failure likely to occur with stock bolts in place or is it usually only a problem after the head is reinstalled?

Reply #5December 29, 2009, 04:18:06 pm

maxfax

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Re: Why do I want "expensive" head studs for a 1.5 or early 1.6??
« Reply #5 on: December 29, 2009, 04:18:06 pm »
THe problem seems to make itself known after re-installing the head..   It usually seems to happen during the retorque after 1000 miles.. Although it has happened when initially installing the head as well..

I think if everything it working fine I would leave well enough alone..   When the time comes for a head gasket, that would be the time for studs...

Reply #6January 01, 2010, 08:50:22 pm

Turbinepowered

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Re: Why do I want "expensive" head studs for a 1 5 or early 1 6
« Reply #6 on: January 01, 2010, 08:50:22 pm »
I tried water but it didnt keep them in place....wats the best for making them stay in place without using that special glue?

What special glue, and hold what in place?

Reply #7January 08, 2010, 05:12:17 pm

Possum79

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Re: Why do I want "expensive" head studs for a 1.5 or early 1.6??
« Reply #7 on: January 08, 2010, 05:12:17 pm »
Here is a picture of my cracked 1.5 Also bent a rod on this sucker.
1979 VW Rabbit Diesel L
My car may be ugly but im addicted to it.

Reply #8June 16, 2010, 12:32:47 am

79rabbit4dr

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Re: Why do I want "expensive" head studs for a 1.5 or early 1.6??
« Reply #8 on: June 16, 2010, 12:32:47 am »
If anyone woudl happen to have a pic of [...] a gasser head bolt I would be grateful if you could throw that up on here.. 

I know this post is old but it was referenced recently so I thought I'd add what I have

http://www.vwdiesel.net/forum/index.php?topic=17027.60

the second post down shows an 11mm gasser head bolt, 11mm diesel head bolt, and 12mm diesel head bolt. ALL are triple square head bolts (as you can see in the pix).

-gasser head bolt - 11mm triple square
-my used diesel engine bolt - 1mm triple square
-new bolts - 12mm triple square





as you can see in the above pix, the gasser ones (top) all have that step-up right after the threads whereas the diesel ones i removed (middle) and the newly purchased ones (bottom) don't.
Paul
LOCATION = Idaho 83440
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1979 Rabbit 4dr Gasser - For Parts
1981 Rabbit 4dr Diesel - For Parts
1981 Rabbit Pickup 1.6 NA - For Parts
1983 Jetta Coupe 1.6 TD - Feeler Part out
1997 Jetta VR6 - Part Out

Reply #9June 16, 2010, 01:02:11 pm

Rabbit on Roids

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Re: Why do I want "expensive" head studs for a 1.5 or early 1.6??
« Reply #9 on: June 16, 2010, 01:02:11 pm »
CRACKED BLOCK PICTURES?!?!?!!!

i will be right back..  ;)