BEST OEM-SIZED 11MM HEAD BOLTS ?
#1
BEST OEM-SIZED 11MM HEAD BOLTS ?
As title.
I'm thinking of upgrading to STi v.3 or 4 cyl heads (to make the most of a 20g+supp mods to be fitted at the same time), so was thinking which are the best (strongest) uprated cyl head bolts to buy? Cosworth?
I'm only going for the OEM-sized 11mm diameter ones, as I'm sure they're more than adequate for <400bhp.
I'm thinking of upgrading to STi v.3 or 4 cyl heads (to make the most of a 20g+supp mods to be fitted at the same time), so was thinking which are the best (strongest) uprated cyl head bolts to buy? Cosworth?
I'm only going for the OEM-sized 11mm diameter ones, as I'm sure they're more than adequate for <400bhp.
Last edited by joz8968; 27 February 2010 at 07:10 PM.
#2
Scooby Regular
The high tensile Cosworth bolts seem to do the trick. Not cheap though, but make sure you get the right ones and not the normal Cosworth Head Bolts I used them on my recent build, which is a tad more than 400bhp.
#7
Scooby Regular
I have no idea how the regular Cosworth studs relate to the OEM ones. The regular Cosworth studs are the same as the ARP's, which come in at around £200.
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#10
Roger Clark Motorsport - RCM Product Detail
Apparently, the regular Cosworth 11mm ones have a tensile strength of 180,000psi or 12,400bar!!! I'm sure they'll be fine
Apparently, the regular Cosworth 11mm ones have a tensile strength of 180,000psi or 12,400bar!!! I'm sure they'll be fine
Last edited by joz8968; 27 February 2010 at 07:51 PM.
#11
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That is the tensile strength of the material.
Normal ARP ones will be sufficient, but for 400hp the stock bolts should be fine too!
Paul
Normal ARP ones will be sufficient, but for 400hp the stock bolts should be fine too!
Paul
#12
Yes stupid me re the tensile strength.
Paul if I do swap out the heads, would you advise on changing the bolts too (the ones you reused/replaced - can't remember - when you did my build). Or do you reckon they'll be okay. What's the price of a set of genuine OEM Subaru 11mm ones?
Paul, purely out of academic interest, what sort of max relative boost pressure can the Cossie, ARP and OEM ones keep a lid on things?
Paul if I do swap out the heads, would you advise on changing the bolts too (the ones you reused/replaced - can't remember - when you did my build). Or do you reckon they'll be okay. What's the price of a set of genuine OEM Subaru 11mm ones?
Paul, purely out of academic interest, what sort of max relative boost pressure can the Cossie, ARP and OEM ones keep a lid on things?
Last edited by joz8968; 27 February 2010 at 08:11 PM.
#13
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Think the answer will always vary to some degree, but for example we have seen up to 2.4 bar on standard ARPs with out issue which is were we stopped, this was with the old style small top locking nut, they have since been improved. Others have seen less and some more im sure.
Personally I would always replace OE bolts if you’re planning on pushing them further, but for piece of mind ARP's over cosy for cost on most applications
Personally I would always replace OE bolts if you’re planning on pushing them further, but for piece of mind ARP's over cosy for cost on most applications
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