ARP main studs or OEM?

[Error404]

Price is about right for good quality hardware i think

[Rusty]

I take it that these are not stretch bolts then, if they are high tensile.

[k.alle]

I'd say you'll be better spending the money on the head studs and SQ washers.

Where do I get my hands on some SQ washers?
Aren't they NLA?

[UrS4boy]

Potential issues with ARP main cap studs

NOTE: It is possible to crush the check valve when installing the No. 3 main cap bolt without the cap or a main cap stud, e.g. an ARP stud that is too long. This can result in the check valve ball being unable to return to its seat when the engine is off. This allows the oil to drain down out of the head when the engine is off. As result, this will lead to wear issues on the camshaft during the period of rotation before the engine oil is again pumped back up into the head. Cam follower ("lifter") performance might also be impacted or compromised by this damaged check valve.

More Check Valve Info here: http://forums.quattroworld.com/s4s6/msgs/96161.phtml

Here is a photo showing both a damaged and a good check valve. You can see how the valve body has been crushed on the valve on the left:

[k.alle]

A good reminder UrS4boy, hopefully the 12.9 M10x80 bolts i bought won't reach the valve.
I've bought a spare valve just in case

[jade]

A good reminder UrS4boy, hopefully the 12.9 M10x80 bolts i bought won't reach the valve.
I've bought a spare valve just in case

One should be shorter, If not you will need to have one machined

[Error404]

NOTE: It is possible to crush the check valve when installing the No. 3 main cap bolt without the cap or a main cap stud, e.g. an ARP stud that is too long. This can result in the check valve ball being unable to return to its seat when the engine is off. This allows the oil to drain down out of the head when the engine is off. As result, this will lead to wear issues on the camshaft during the period of rotation before the engine oil is again pumped back up into the head. Cam follower ("lifter") performance might also be impacted or compromised by this damaged check valve.

More Check Valve Info here: http://forums.quattroworld.com/s4s6/msgs/96161.phtml

Here is a photo showing both a damaged and a good check valve. You can see how the valve body has been crushed on the valve on the left:

More importantly it can be crushed shut stoping oil flow though the head and causing starvation to the head, metallic debris in the oil system and complete engine failure within a few hours

Fit the check value after you have torqued the mains down. If it won't fit then you know you have a problem.

[Laaf]

What's the real benefit of running ARP main studs, at what stage will the OEM ones snap?

Is it because they are reusable?
I'll be running OEM pistons so the engine will be sub 6-700bhp during my ownership, which seems to be for life.

I am curious.
If I take the plunge for ARP main studs I am in the risk of needing a line-honing for the main caps. This seems very unnecessary if OEM ones will suffice.

Has people suffered from OEM main stud failures?

As an example I will be running OEM head bolts, as I'm not planning on removing the head repeatedly.

I'd say running ARP main studs could be used if running a main girdle. But atleast CP-S supply their main girdle with 12.9 bolts so they aren't necessary by any means. This requires line honing anyhow. I run ARP main studs only as I got them quite cheap. Martinsson for instance runs the OEM bolts from memory.
As for the head studs you should get these when going man boost, especially on E85. Lifting the head destroying the head gasket and having you skimming the head and block deck is quite a boring thing to do.

[k.alle]

Thanks for that reply Laaf. Do you know where I can get the sport quattro washers for the head ARP?
I don't have access to old OEM head bolts.

[Error404]

I have loads of old OEM head bolts here, can send you 12 for the cost of post if you need

[Laaf]

The Sport Quattro washers are NLA, but I use the washers supplied with the ARP studs with no problems at all.

[Error404]

Lots of people reported the stock ARP washers sank into the head, its not recommended. Cut the washer off the OEM bolts or get some made

[Jamo]

That was the original washers before they were redesigned, the new ones are fine

[Jamo]

using ARP in the mains is just for piece of mind, depends on your power level. If you have to take the crank out again just onetime the ARP's have paid for themselves as mains are stretch and can't be reused.

No right or wrong here

[Thuppu]

Main bolts cost like 5 euro/kit, so you can change them quite many times before ARP mains have paid themeselfs. But agree on the piece of mind thing.