ARP head stud set for the ST
- Thread starter Ed
- Start date
OP
OP
Well there is no real reason other than the engineering behind the studs and the way they work is more consistent and accurate than say OEM head bolts. Specifically speaking, there would be little advantage say in a normal setup. Its more a case of over engineering, which is something I like to do.
yeah basically when used properly they will clamp tighter and more consistently than the standard bolts. I think they are a very good idea in any rebuild, let along a small, high boost motor like these.
They generally come in about 30-50% more than new, genuine bolts. and you should never reuse head bolts anyway.
They generally come in about 30-50% more than new, genuine bolts. and you should never reuse head bolts anyway.
superls
K10 Tuner
where are the ARP bolts better and how do they enable tightler clamping? as the bolt is only as tight as you tighten it and is still only as strong as the thread in the alu block, the ma bolts arent stretch, so i would have thought if thery were torqued to a set figure how do they have less of a clamping effect then the ARP ones?
OP
OP
frank
Club Member
x2, autodata says not to renew headbolts, and you would need some serious boost to snap a stock headbolt imo
OP
OP
Autodata considers that the car makes about 50bhp/L not 200+.
Your still missing the point, its about over engineering, as opposed for just making do, however there are some areas (such as con-rod bolts) where I consider ARP essential, and a significant improvement over stock.
Your still missing the point, its about over engineering, as opposed for just making do, however there are some areas (such as con-rod bolts) where I consider ARP essential, and a significant improvement over stock.
OP
OP
I knew you'd say that... No they are not made of the same or qualty of material. I think you may risk over clamping standard bolts by using the moly lube.
Again, its the whole system of washers, bolt design lube etc that makes it work, not any one single component.
Again, its the whole system of washers, bolt design lube etc that makes it work, not any one single component.
thank god for links....the easy answer is that studs are a little better.
some reasons:
you mention 'they are torqued to the same figure". actually the arp studs can be tighter due to the grade of steel used and the treatment. ideally you will use a stretch gauge which measures the actual tension, not a torque wrench which guesses the tension based on how much effort it takes to twist the fastener. they are rated to 190,000psi ish instead of around 120,000psi for a common head bolt.
bolts turn when you tighten them, with studs only the nut turns. this means the torque you are putting into it (and measuring) is spent only on turning the fastener not the whole bolt. much more accurate.
arp approach benefits:
arp cut the thread after heat treatment not before. this means when the thread is rolled in it is stronger at the points that take the most load. if you cut the thread then heat treat the resulting thread has even strength at the low and high stress points
arp design studs at the right length for the nut - the point where the nut/thread engages is the weakest on the fastener.
fine thread on top end = higher clamping at the same torque
fastener design - they have been very careful with design like wider diameter at the stressed area (threads), gentle radius to protect against stress raisers (were fatigue cracks start), machining for straightness last etc.
reasons some people say are a benefit but are not:
studs locate the head correctly. no way, jose. bolts are designed to clamp not hold in shear ie sideways movement. dowels are designed to locate a head properly
basically - I would expect a more reliable head to block seal under harsh conditions. I might only be 20% better but maybe that will make the difference
some reasons:
you mention 'they are torqued to the same figure". actually the arp studs can be tighter due to the grade of steel used and the treatment. ideally you will use a stretch gauge which measures the actual tension, not a torque wrench which guesses the tension based on how much effort it takes to twist the fastener. they are rated to 190,000psi ish instead of around 120,000psi for a common head bolt.
bolts turn when you tighten them, with studs only the nut turns. this means the torque you are putting into it (and measuring) is spent only on turning the fastener not the whole bolt. much more accurate.
arp approach benefits:
arp cut the thread after heat treatment not before. this means when the thread is rolled in it is stronger at the points that take the most load. if you cut the thread then heat treat the resulting thread has even strength at the low and high stress points
arp design studs at the right length for the nut - the point where the nut/thread engages is the weakest on the fastener.
fine thread on top end = higher clamping at the same torque
fastener design - they have been very careful with design like wider diameter at the stressed area (threads), gentle radius to protect against stress raisers (were fatigue cracks start), machining for straightness last etc.
reasons some people say are a benefit but are not:
studs locate the head correctly. no way, jose. bolts are designed to clamp not hold in shear ie sideways movement. dowels are designed to locate a head properly
basically - I would expect a more reliable head to block seal under harsh conditions. I might only be 20% better but maybe that will make the difference
superls
K10 Tuner
ed the link as far as i can see is in relation to big end bearing bolts, which i could sort of justify the need, but im still not convinced by head bolts/stude, ive seen lots of engines in my uncles garage and my dad bought a transit engine where the timing belts/ chains etc have snapped or had trouble, it bends valves, rods, cams, the engine my dad bought it broke the aluminium rocker box on the head, you caould actually see where the piston had left an indentation on the head, but the head bolts wernt broke or even damaged or bent.
superls
K10 Tuner
i see some really valid points there duncan, if you were building a engine from the ground up, with all new parts, and it was intended to have any sort of preformance then its really a no brainer to use them especially if there were similar in price to the oem unit, my case was there not 100% necessary for every engine on the road.
yeah that's exaclty how i look at it too.
btw...should i wander elsewhere on these forums? my car handles like a bucket of #### but it sounds like there is a thread somewhere else i should know about. I had no luclk chasing down info from the k10 cup racers despite a couple of different contacts in japan
OP
OP
On an engine where tolerances are tight and normal gasket materials are not being used i.e. copper with no 'give' to it, your guaranteed a much more uniform and consistent level of torque across your head bolts (or any for that matter) using the ARP system. Much of the torque applied to bolts is friction in turning them, as well as the clamping force, and it can vary a lot between bolts. ARP researched this on theirs and using their bolt lube with their studs allows very precise and accurate clamping loads across all the head bolts. It could make the difference between a headgasket sealing - or not, under very high loads. That's why for most here its overkill. Very very few are intending to push huge power from such small capacity.
