As David says, you gotta tighten down ya head bolts by degrees, in stages, not torque. Because you are using “torque to yield bolts,” they are made different, to suit modern engine design, most are now using this system. The old way of torque each bolt by tension wrench was done using bolts that were not as elastic and known as torque bolts.
jamesmartin
Well-Known Member
40 nm the 60 degrees which is one flat of bolt better than angle guage for ease the another 60 degrees then the 10 bolts around cylinders and extra 20 degrees,just mark each bolt on head with line and turn one flat mark each bolt with a line after tightening so you know its been done as theres no way of checking like torque setting,they are used with aluminum heads as the expand more than cast iron or steel when heated
Codbasher
New Member
So you are looking 1/5 of a turn on a 5 sided head then??
Have decided in this case then to get a new set of head bolts, as the old ones using this method must be stretch ones, rather than the good old fashioned screw em down with a bar on a cracking bar type
Did go out and get a degree thingy today, so will try that, cant get the hang of this modern techno stuff you know........
Have decided in this case then to get a new set of head bolts, as the old ones using this method must be stretch ones, rather than the good old fashioned screw em down with a bar on a cracking bar type
Did go out and get a degree thingy today, so will try that, cant get the hang of this modern techno stuff you know........
jamesmartin
Well-Known Member
bolts have 6 sides 360 dived by six = 60 degrees stretch bolts can be used several times no need for new unless damaged , i reuse them all the time, the main thing is you tigthen from middle out wards and mark bolt heads so you know where you are
The possibility of failure through reusing torque to yield bolts is very high, especially on a head gasket, it puzzles me why anyone would risk all that time, expense and effort they put into rebuilding the top of an engine, for the cost of a few new bolts, they would be the cheapest component of the rebuild FFS.
Tuskenraider
New Member
You can generally use stretch bolts upto 3 times unless stated that you must not reuse them. The trouble is unless you put them in new you have no idea how many times they have been used. They only cost about £20 so just get new ones
Codbasher
New Member
You can generally use stretch bolts upto 3 times unless stated that you must not reuse them. The trouble is unless you put them in new you have no idea how many times they have been used. They only cost about £20 so just get new ones
Give Deeside 4x4 a ring, they want £50 a set, + VAT lol.
And people wonder why I wont use them.....
jamesmartin
Well-Known Member
i use new bolts when reconditioning engines but often use the old bolts when just renewing head gasket where it hasnt been cooked you can check bolts by comparing them all by size ie the 10 long bolts are all the same size and the same with others ,ive done alot and never bust one yet or had a complaint and most are long time customers ,theres more chance of over heated head after skimming moving again during heating with new bolts than a head that hasnt been overheated moving with good used bolts,new bolts might be best practice but not allways necessary
Access Denied
New Member
Do yourself a favour and get/use new bolts. TTY (Torque To Yield) should NOT be re-used. You are torqueing the bolts to the point of yield and then fractionally beyond. Once they have reached yield point the elasticity in the bolt is lost forever! Therefore they cannot be torqued to manufacturers spec again.
Why risk an HG failure, or worse? Why risk spending and doing the job twice when it can be done 'right' once?
The Haynes manual specifically states "Do Not Re-use"!
Example:
Take 1 new bungee strap and measure it's free length.
Stretch it until it's impossible to stretch it any further and leave it over night under tension.
Release the tension and measure the free length again. It should read 'knackered' on the tape measure!
Bear in mind that when the TTY bolts are under stress to the point of just beyond yield, they then need to stretch again under heat load of the engines daily/weekly/monthly/annuall cycle.
Do you really want to risk it?
Why risk an HG failure, or worse? Why risk spending and doing the job twice when it can be done 'right' once?
The Haynes manual specifically states "Do Not Re-use"!
Example:
Take 1 new bungee strap and measure it's free length.
Stretch it until it's impossible to stretch it any further and leave it over night under tension.
Release the tension and measure the free length again. It should read 'knackered' on the tape measure!
Bear in mind that when the TTY bolts are under stress to the point of just beyond yield, they then need to stretch again under heat load of the engines daily/weekly/monthly/annuall cycle.
Do you really want to risk it?
jamesmartin
Well-Known Member
well if haynes states it it must be right ,i used to work at engine reconditioners and they reused them all the time they didnt get failures in use or through fastening ,where as they do stretch they arent at point or near point of yield ,if they where they wouldnt clamp head,i would suggest new bolts but i think you protest to much making those that did reuse them worry over something they neednt
Access Denied
New Member
Similarly if you say 'they reused them all the time' and that 'they aren't at the point or near point of yield' you must be right?
They are called 'torque to yield' because?
'Yield' means?
All bolts stretch, TTY or otherwise and so 'yield' is in the description/design for a reason, don't you think?
