Head bolt torque-hot vs cold?
gr8...@ix.netcom.com
I've encountered differing opinions as to when you're supposed to torque
engine head bolts to factory specs - some say when the engine is hot,
some say cold. Nobody seems sure. To my mind, logic says it's "cold"
because they certainly don't fire up the engines on the factory assembly
lines before tightening down the head bolts?! On the other hand...does
it matter? Thanks.
Ken Payne
gr8...@ix.netcom.com wrote:
Cold. Also, its easier to strip out a bolt hole hot.
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sbl...@linknet.net
>I've encountered differing opinions as to when you're supposed to torque
>engine head bolts to factory specs - some say when the engine is hot,
>some say cold. Nobody seems sure. To my mind, logic says it's "cold"
>because they certainly don't fire up the engines on the factory assembly
>lines before tightening down the head bolts?!
What do they intend on doing to warm the entire motor???
You can't run the engine with the heads untoruqed!
Tq them to factory spec unless you changed bolts and/or heads then
follow there reccomendation. Alway do it in steps. If the head needs
to be at 65, then start at 45 and follow the sequence then up to 55
and repeat untill you have done them all up to 65.
This ensures even clamping force without pinching or overtightning.
Small Block
Chevy Mania
Jack Stands.
For the most part alloy heads are to be tensioned cold that includes
retension and cast iron heads will require a hot retension after initial
startup always check the book for the exact tension sequence and hot or
cold specs.
If its cold and you do it hot it may pull the studs or bolts in the threads
or even crack the head. If its an overhead cam definitely get it right or
you might wake up to a broken cam on you first morning startup.
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gr8...@ix.netcom.com wrote in article <333C74...@ix.netcom.com>...
> I've encountered differing opinions as to when you're supposed to torque
> engine head bolts to factory specs - some say when the engine is hot,
> some say cold. Nobody seems sure. To my mind, logic says it's "cold"
> because they certainly don't fire up the engines on the factory assembly
Clarence Snyder
On Fri, 28 Mar 1997 17:46:00 -0800, gr8...@ix.netcom.com wrote:
>I've encountered differing opinions as to when you're supposed to torque
>engine head bolts to factory specs - some say when the engine is hot,
>some say cold. Nobody seems sure. To my mind, logic says it's "cold"
>because they certainly don't fire up the engines on the factory assembly
>lines before tightening down the head bolts?! On the other hand...does
>it matter? Thanks.
What does the manufacturer's manual say? It is always specified either
hot or cold, and wqheather to assemble dry or oiled.
As a rule of thumb, all alloy heads are torqued cold. Cast Iron heads
are torqued warm.
Older engines / head gaskets used to require retorquing. Most modern
gaskets are of the "uni-torque" variety and are not to be retorqued.
Check the instructions with the new gasket.
Many engines today use "stretch to yeild" head bolts. These MUST be
replaced when replacing head gaskets. When they break off a month or
two down the road, they ALWAYS cause problems. These bolts can be
identified by the torquing instructions - torque to X ft lbs torque
then an additional 1/x turn.
Snyder Enterprises
Appropriate Technology for the Information Age
Waterloo Ontario.
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