Head Stunds

[Sweeper]

Looking for a set of standart Head Studs or Arp Head Studs.

Quite urgently

Thanks.

[caterpillar]

go to the HARDVAREstore,get some umbrako or torx long bolts,with 12,8 steel.....cheep and useful......they will not stretch like the org stretchbolts.....!!

[Mihnea]

@caterpillar: does that mean he will have to retighten the bolts after 5000kms? what do you do about the different ways in which bolts take the stresses and so on?

it sounds like a cheap good idea to me, but IMHO not what you want to use on an engine, even if it has stock HP...

HTH,

Mihnea

[caterpillar]

Think its a good idee.you have too retigthen one time with 1000km.... the org bolt on the main bearing are only 10mm and 10,9 steel quality.... have not use too retigthen them??? i will change the org main bearing bolt too 12,8 steel umbako.....cost pennies. same to the head i think.....i will tighten the thread out of the block,before the bolt will break,i think....

[Lee]

Stretch bolts are named thus because they are designed to stretch (plastic deformation i.e. tensioned beyond their yield point). If you understand materials and look at a stress vs strain plot of a stretch bolt in a yielded state you will understand why they are designed like that and why they are used in cylinder head applications. Main bearing bolts are not stretch bolts. A lot of effort goes into designing fasteners for their application for a very good reason and it takes an understanding of material science to understand why.

ARP studs are designed not to stretch and I believe they exceed the 12.9 grade of Unbrakos (Unbrakos are great bolts, I have used them in many high stress applications for this reason). ARP studs are recomended over stretch bolts as they are reusable and are supplied as studs and nuts so that the stud can be held still with an allen key during tightening to ensure that they do not twist when the nut is torqued to the recommended level. Unbrakos will twist and relax so even with retightening I am not sure I would use them myself to hold a head in place unless they are retorqued at least once. Personally I would stick with standard stretch bolts (not reusable) or ARP studs and nuts (reusable).

Lee

[91_S2]

That was a valuable clarification Lee. Thanx.

[caterpillar]

ok. i remind that. but it a cheap alternativ for people without/less money

[Lee]

I do use Unbrakos on many chassis applications instead of standard bolts. They are good.

[Sweeper]

Great , but I still need the bolts . Not gonna use anything that i need to retight. Just want to put them and forget.

Anyone ?

[diesel des]

Anyone know the UK distributer af ARP? Or Raceware. Thanks,des.

[diesel des]

What is the thread of the block for the head studs. M11 x? . Also what is the lenth of the stock bolt. Im thinking of some 14.9 (yes they do exist!) bolts. They have a tensile strength of 180,000 psi. The ARP are 190,000 -200,000 psi. A good 12.9 is 153,000 and a 8.8 is 92000psi. What is the grade of the OEM bolt?

[Sweeper]

problem solved , bought new ones.

[caterpillar]

where can you get 14.9 steel bolts??? i've never seen that... and i have do some mecanik works......

[diesel des]

Their are a few companies in england that can make them. http://www.andrewsfasteners.co.uk/pg1.htm is one. Anyone know the pitch of a stock bolt?

[Lee]

What is the grade of the OEM bolt?

Stretch bolts aren't graded in the same way. IIRC the 12.9 refers to the two values of yield stress (900N/mm^2 or was it 90% of UTS, can't remember) versus ultimate tensile stress (1200N/mm^2) of the bolts...bit misleading for a stretch bolt to be quoted in the same way.