RV8 Head Bolts or Studs
Discussion
Chassis 33 said:
Which are stronger/better in peoples experience head bolts or head studs on a RV8 engine (with 10holes not 14)?
Regards
Iain
Studs are always better then bolts from an engineering perspective. You get greater clamping forces and there is far less strain on/within the block.Regards
Iain
Boosted.
Chassis 33 said:
Cheers, I've never really fathomed that one, is it something along the lines of you only apply axial load to the block when torquing a nut onto a stud, whereas a bolt applies both an axial and rotational load as its torqued?
Regards
Iain
I think that's pretty much it. If you tighten a bolt then you're left with tension and torque varying down its length. If you tighten up against a stuff then only the tension varies. Also, having the bolt rotating as it is loaded up must surely mean that static friction is not on your side.Regards
Iain
A stud becomes apart of the parent metal and when you tighten the nut more of the tensile load is applied at the nut end. Studs also come with rolled threads so for a given torque you get more clamping force due to less friction.
A bolt is applying more strain on the threads within the block and wearing them out each time you tighten it up.
Boosted.
A bolt is applying more strain on the threads within the block and wearing them out each time you tighten it up.
Boosted.
Howitzer said:
When torqueing bolts to 650lbs and on some applications even greater, we are told to use only engine oil. On bolts where you stretch the stud with a jack at say 800 odd pounds, you also only use engine oil.
Why is oil not ok but copper grease etc ok?
Dave!
Grease is thicker so will effect torque readings. I'd stick with the recommendations.Why is oil not ok but copper grease etc ok?
Dave!
Boosted.
sorry to be pedantic.......but you shouldnt be using torque as a means of accurate fastner clamping......by all means use a small torque figure say 10Nm as an initial bedding setting.....after that you shoyuld be using an angle gauge.
I'm currently working on an engine design contract in Ford-Dagenham engine plant, and believe me - they have a LOT of problems with bolts shrearing on the production line due to using torque and a bit of lubicant gets in the way, or the fastner coating varies......so why do they use torque I hear you ask?......because its cheap......when they hit a problem with fastners, they then use angle every time.....
also from my days of working in professional race engine design, the engine builders always used an angle gauge when tightening critical fastners like head, con-rod and main cap bolts.
go buy a cheapo angle gauge and start using it!
I'm currently working on an engine design contract in Ford-Dagenham engine plant, and believe me - they have a LOT of problems with bolts shrearing on the production line due to using torque and a bit of lubicant gets in the way, or the fastner coating varies......so why do they use torque I hear you ask?......because its cheap......when they hit a problem with fastners, they then use angle every time.....
also from my days of working in professional race engine design, the engine builders always used an angle gauge when tightening critical fastners like head, con-rod and main cap bolts.
go buy a cheapo angle gauge and start using it!
The problem with that is you first need to find out what angle equals what torque or clamping force.
The only real way to do it is to screw on a jack, stretch or pull the 2 clamping faces together and then do the nut up finger tight.
For vehicle applications where it is done with care by hand (Not using power tools) then torque settings should be fine.
Just follow the manufacturers instructions.
Sorry Boosted, was just an open question as I wasn't sure if there was a reason for using anything other than oil on smaller applications as i'd never heard of it.
Dave!
The only real way to do it is to screw on a jack, stretch or pull the 2 clamping faces together and then do the nut up finger tight.
For vehicle applications where it is done with care by hand (Not using power tools) then torque settings should be fine.
Just follow the manufacturers instructions.
Sorry Boosted, was just an open question as I wasn't sure if there was a reason for using anything other than oil on smaller applications as i'd never heard of it.
Dave!
. Pukka piece of kit.I have never read such a load of old tosh (except Mr Knighty).
There are a couple of advantages of using studs but they certainly have nothing to do with increasing clamp load.
Automotive joints are designed to require a given clamp load as provided by the factory recommended angle tightening regime (these days). The torque/angle recommendation results in the required bolt tension.
You can't just stick in and wind down some fine threaded studs without risking either pulling the stud from the block or distorting the head. What you need to know, and ARP will tell you if you ask, what equivalent torque is required on their fine thread studs to give the same clamp load as the recommended (torque/angle) load for the original fixings.
A good/valid reason for using studs eg in a race engine, would be to avoid potential thread damage in the block where repeated rebuilds are the order of the day - you can replace a stud easily - not so easy to repair a block. If you must use a torque wrench as your tightening method (DON'T if the manufacturer specifes angle tightening (and they probably do)) then potentially the finer thread normally found on studs may result in more consistent clamp loads.
Russ
There are a couple of advantages of using studs but they certainly have nothing to do with increasing clamp load.
Automotive joints are designed to require a given clamp load as provided by the factory recommended angle tightening regime (these days). The torque/angle recommendation results in the required bolt tension.
You can't just stick in and wind down some fine threaded studs without risking either pulling the stud from the block or distorting the head. What you need to know, and ARP will tell you if you ask, what equivalent torque is required on their fine thread studs to give the same clamp load as the recommended (torque/angle) load for the original fixings.
A good/valid reason for using studs eg in a race engine, would be to avoid potential thread damage in the block where repeated rebuilds are the order of the day - you can replace a stud easily - not so easy to repair a block. If you must use a torque wrench as your tightening method (DON'T if the manufacturer specifes angle tightening (and they probably do)) then potentially the finer thread normally found on studs may result in more consistent clamp loads.
Russ
russell_ram said:
I have never read such a load of old tosh (except Mr Knighty).
Russ
My take is that for the same applied torque value you will get increased clamp because a fine rolled thread under the nut offers less friction then a coarse bolt thread so the nut will be wound down further. Russ
Another thing I've observed is the much higher torque values quoted by the likes of arp when using their head studs, block studs or rod bolts. Arp warn users to check bores for ovality and I've frequently found the bores on conrods to become 'out of round' when fitting arp's. Something's distorting them and arp know it's because of increased clamp. The only thing that's changed over stock is the torque setting which they provide for those who haven't got a stretch guage.
I also think that a waisted stud allows more even spread of tensile forces within the stud when compared to a bolt which has a parrallel shank. This allows a higher tensile value to be obtained when using a stud before the yield point is reached. So we can apply more torque/clamp because of this.
Boosted.
Edited by Boosted LS1 on Thursday 14th June 16:31
Ian,
You may find some of the comments posted on this bb of interest. Some of them seem to have it sussed, say no more
.
http://www.v-8.org.uk/forum/viewtopic.php?t=1364
Boosted.
You may find some of the comments posted on this bb of interest. Some of them seem to have it sussed, say no more
.http://www.v-8.org.uk/forum/viewtopic.php?t=1364
Boosted.
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