corfunightmare
New Member
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- 13
I'm about to remove the heads and replace the gaskets, does anyone know if there are any precautions i need to take when removing. Also do I have to use new head bolts or can I get away with using the old ones.
If you torque all the bolts to a specified torque for that size of bolt (old school) you know, that every bolt has exactly the same clamping force. If you turn a bolt through 90deg & 90deg again there is no way you can guarantee that all the bolts are exactly at the same (clamping force) because the dial gauge you are turning with, as a human being you will never get them all the same, however with the click of a calibrated torque wrench you will.
Gomog, may I ask from what experience you are quoting ref . stretch bolts?
(If you try to use them twice, they can twist like liquorice and snap like plastic)
Yes I agree somewhat with that statement, if the bolt is knackered & has not been checked properly by an experienced person it will snap, like any other bolt, stretch or non stretch.
Bolts that are adjacent to the exhaust manifold can fail, if an engine is allowed to persistently overheat, the elasticity of the bolt may fail leading to a gasket failure, on examination should be replaced.
Wheel nuts on trucks (HGVs) are stretch studs, with a flat face nut & are tightened in the region of 475lbsft & it is the clamping force of the combined elasticity of the stud & the torque of the nut that holds the wheel on. Wheels are removed from trucks as a matter of course during maintenance & rarely is a stud/nut replaced unless it is damaged.
The quality steel bolt on an alloy cylinder head is only torqued to 65-70lbsft. If a bolt is examined properly it can be safely used more than once.
(Remember the chap/designer who put 3 rows of bolts on the cylinder head, everyone believed he was right, until someone came up with the 2 row head?)
If you torque all the bolts to a specified torque for that size of bolt (old school) you know, that every bolt has exactly the same clamping force. If you turn a bolt through 90deg & 90deg again there is no way you can guarantee that all the bolts are exactly at the same (clamping force) because the dial gauge you are turning with, as a human being you will never get them all the same, however with the click of a calibrated torque wrench you will.
I have discussed this with some engine re-manufactures who rebuild engines all day long & they use the torque method, why, because sometimes at their cost without a torque wrench to regulate the tightening, a bolt as damaged a cylinder head & or pulled the threads on the block, old school vers. new school. the argument will never be settled.
Do you replace all the injectors/spark plugs/glow plugs when only one has failed? do you fit dampers/tyres/springs/airbags etc. in pairs? do you change all the bulbs when one has failed? without testing, do you change your antifreeze, all the oils to soon? if the answer is yes, the manufactures are rubbing their hands in profit as you are a paid up member of the fit new brigade.
Gomog, may I ask from what experience you are quoting ref . stretch bolts?
gomog said:(If you try to use them twice, they can twist like liquorice and snap like plastic)
Yes I agree somewhat with that statement, if the bolt is knackered & has not been checked properly by an experienced person it will snap, like any other bolt, stretch or non stretch.
The quality steel bolt on an alloy cylinder head is only torqued to 65-70lbsft. If a bolt is examined properly it can be safely used more than once.
(Remember the chap/designer who put 3 rows of bolts on the cylinder head, everyone believed he was right, until someone came up with the 2 row head?)
If you torque all the bolts to a specified torque for that size of bolt (old school) you know, that every bolt has exactly the same clamping force. If you turn a bolt through 90deg & 90deg again there is no way you can guarantee that all the bolts are exactly at the same (clamping force) because the dial gauge you are turning with, as a human being you will never get them all the same, however with the click of a calibrated torque wrench you will.
I have discussed this with some engine re-manufactures who rebuild engines all day long & they use the torque method, why, because sometimes at their cost without a torque wrench to regulate the tightening, a bolt as damaged a cylinder head & or pulled the threads on the block, old school vers. new school. the argument will never be settled.
Do you replace all the injectors/spark plugs/glow plugs when only one has failed? do you fit dampers/tyres/springs/airbags etc. in pairs?
Gomog, may I ask from what experience you are quoting ref . stretch bolts?
gomog said:(If you try to use them twice, they can twist like liquorice and snap like plastic)
Yes I agree somewhat with that statement, if the bolt is knackered & has not been checked properly by an experienced person it will snap, like any other bolt, stretch or non stretch.
The quality steel bolt on an alloy cylinder head is only torqued to 65-70lbsft. If a bolt is examined properly it can be safely used more than once.
(Remember the chap/designer who put 3 rows of bolts on the cylinder head, everyone believed he was right, until someone came up with the 2 row head?)
If you torque all the bolts to a specified torque for that size of bolt (old school) you know, that every bolt has exactly the same clamping force. If you turn a bolt through 90deg & 90deg again there is no way you can guarantee that all the bolts are exactly at the same (clamping force) because the dial gauge you are turning with, as a human being you will never get them all the same, however with the click of a calibrated torque wrench you will.
I have discussed this with some engine re-manufactures who rebuild engines all day long & they use the torque method, why, because sometimes at their cost without a torque wrench to regulate the tightening, a bolt as damaged a cylinder head & or pulled the threads on the block, old school vers. new school. the argument will never be settled.
Do you replace all the injectors/spark plugs/glow plugs when only one has failed? do you fit dampers/tyres/springs/airbags etc. in pairs?
Gomog, may I ask from what experience you are quoting ref . stretch bolts?
gomog said:(If you try to use them twice, they can twist like liquorice and snap like plastic)
Yes I agree somewhat with that statement, if the bolt is knackered & has not been checked properly by an experienced person it will snap, like any other bolt, stretch or non stretch.
The quality steel bolt on an alloy cylinder head is only torqued to 65-70lbsft. If a bolt is examined properly it can be safely used more than once.
(Remember the chap/designer who put 3 rows of bolts on the cylinder head, everyone believed he was right, until someone came up with the 2 row head?)
If you torque all the bolts to a specified torque for that size of bolt (old school) you know, that every bolt has exactly the same clamping force. If you turn a bolt through 90deg & 90deg again there is no way you can guarantee that all the bolts are exactly at the same (clamping force) because the dial gauge you are turning with, as a human being you will never get them all the same, however with the click of a calibrated torque wrench you will.
I have discussed this with some engine re-manufactures who rebuild engines all day long & they use the torque method, why, because sometimes at their cost without a torque wrench to regulate the tightening, a bolt as damaged a cylinder head & or pulled the threads on the block, old school vers. new school. the argument will never be settled.
Do you replace all the injectors/spark plugs/glow plugs when only one has failed? do you fit dampers/tyres/springs/airbags etc. in pairs?
Personal experience of course. And the scores of times trying to clean up after those who tried to reuse these things and had the results I describe.
I think he heard you the 1st time.
I see you a fully paid up member of the “fit new brigade” & cannot judge the wear of component, have little or no diagnostic capabilities therefore just fit new.
The motor factors rub their hands when you walk in the door. As regards my P38 it's 10 yrs old & is in very "mint" condition with plenty of tlc, not fnb.
Hi Guys,
Just shows the importance of a non blocked Rad.
Thanks again boys, this site is the best for info.
Regards to all,
Andy.
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