Date: Sat, 21 Mar 2015 11:13:19 -0700
Reply-To: thewestyman <zolo@FOXINTERNET.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: thewestyman <zolo@FOXINTERNET.NET>
Subject: Re: Head stud testing
In-Reply-To: <BAY405-EAS204507AB1B3D9DC6F6EA491A00F0@phx.gbl>
Content-Type: text/plain; format=flowed; charset="UTF-8"; reply-type=original
Dennis,
You are the best there is in Vanagon World.
"If the heads are loose, the studs are stretching" I did not understand
this. If the head is loose the bolts are still not tightened, I think, and
thus nothing is stretching yet. But you must have meant it differently, I'm
sure.
The other thing; I have a real hard time taking studs out, never mind
wanting to change them all anytime I would like to. I have an engine with a
stud half of it broken, I can get to it to apply power to turn it, I can
heat the block and the stud with a torch (oxy-acet), yet it wont' budge.
What is the most I can do to it?
Regards,
Zoltan
-----Original Message-----
From: Dennis Haynes
Sent: Saturday, March 21, 2015 7:19 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Head stud testing
The Vanagon head stud application is a bit unique. Due to the different
materials in the case, heads, cylinders and the studs themselves thermal
expansion becomes the real problem. As designed, properly installed the
studs actually stretch and get turned into springs. In addition to this
stress they also get attacked by corrosion or worse erosion. Yes, these can
suffer the same effects as happens in diesel engines. Micro bubbles form in
the coolant and combustion impulses make vibrations that when these bubble
break some metal goes with them. Real diesel engines use special antifreezes
or additive systems to combat this. Ford learned the hard way with the power
strokes years ago as this actually began putting holes in the cylinders.
Whenever doing head work you want to do a test installation and make sure
all the studs can torque up to 41 ft. lbs. without excessive twisting. Ones
that keep twisting and snap back more than say 1/16 turn are probably no
good. If the engine was severely over heated it is probably best to replace
them all. I also believe in replacing the head nuts or at least cleaning the
threads with a high quality tap. Any thread friction will affect the final
clamp load after torqueing. This is why many critical applications now
torque to some lower number and then add some number of turns. This is also
used for applications where the fastener is being torqued to yield like some
rod bolts.
If the engine is together and running it may be best to don’t try to fix
what is not broken. If you have trouble with combustion gasses getting into
the cooling system the first step is to check head torque. I have fixed many
of these over the years this way. Keep in mind that except for incorrect
installation if the heads are loose, the studs are stretching. A broken stud
always means head removal and possible cylinder removal. If the stud breaks
low it is engine out, apart, and off to a machine shop with some good
milling equipment.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Richard Koller
Sent: Saturday, March 21, 2015 8:17 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Head stud testing
Dennis/List,
I noticed that you have mentioned testing head studs a couple times on the
list recently. I have an engine with a snapped head stud that ambushed me.
This engine was maintained properly with regular coolant changes etc no
overheating ( at least in my hands ) ran very well. Anyway, I have an
interest in preventing a recurrence of this but I don' t know how to go
about testing head studs. What's the procedure that is recommended.
Thanks
Rick Koller