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retightening new head bolts ARP2000 in my case

PostPost by: el-saturn » Thu Jun 29, 2017 9:44 pm

i dont agree gentlemen, but scientific proof YOU have may change my opinion! a sealed surface (using an ajusa modern head gasket) got the initial required torque which SEALS - why would you want to disturb a perfect static sealing situation just to relax the tension on the bolts which one generates while squeezing everything together: so in my opinion (even with 1nce used arps) add another 0.25 or 0,5 kgm instead of the above suggested procedure -- LOOKING forward to answers sandy PS my new 701 still doesnt leak after 100mls
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PostPost by: Hawksfield » Fri Jun 30, 2017 11:06 am

Hi

I have original bolts and have never retightened after torqueing to the manual spec. I have had the head off a number of times due to other reasons than gasket problems is it necessary ?
Always welcome other views and improved practices
Regards

John

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PostPost by: promotor » Fri Jun 30, 2017 11:14 am

Personally I don't see the problem - it's not like you are completely relaxing the torque of the head bolts, just lessening it slightly.It's a fairly safe method to loosen them and bring them back up to the relevant torque provided there is already sufficient lubrication under the head and on the threads.

I feel that it gives a better sense of being at the correct torque after everything has settled/compressed/relaxed.
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PostPost by: rgh0 » Fri Jun 30, 2017 11:19 am

Hi Sandy

The head gaskets are not perfectly elastic and compress over time during the initial heat and cool cycles.

Using a composite fibre gasket on a high compression race engine with the high stresses that racing puts on it i find it can be tightened down two or three times before it stops moving. I tightening after running in and I normally check it after a couple of races and it moves a little more and then check after about 5 races at which point it has stopped moving

A road engine general requires only one subsequent tightening after a couple of hundred km running in and when I check it again at 1000 km it does not move further.

Normally I first try the bolts or nuts at original torque, then I try a couple of foot pounds higher. If they don't move I crack them off and re-tighten at the original torque and see if they turn beyond the location originally set before I cracked them.

If your head is to soft then the bolts keep sinking as you do this and they never stabilise.

cheers
Rohan
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cheers
Rohan
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PostPost by: Galwaylotus » Fri Jun 30, 2017 6:32 pm

rgh0 wrote:Hi Sandy

The head gaskets are not perfectly elastic and compress over time during the initial heat and cool cycles.

Using a composite fibre gasket on a high compression race engine with the high stresses that racing puts on it i find it can be tightened down two or three times before it stops moving. I tightening after running in and I normally check it after a couple of races and it moves a little more and then check after about 5 races at which point it has stopped moving

A road engine general requires only one subsequent tightening after a couple of hundred km running in and when I check it again at 1000 km it does not move further.

Normally I first try the bolts or nuts at original torque, then I try a couple of foot pounds higher. If they don't move I crack them off and re-tighten at the original torque and see if they turn beyond the location originally set before I cracked them.

If your head is to soft then the bolts keep sinking as you do this and they never stabilise.

cheers
Rohan
ps relaxing with a nice Wolf Blass Grey label shiraz

cheers
Rohan

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