ARP main studs or OEM?

[k.alle]

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.

[Rusty]

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

If you do go for the mains, then be careful of the return valve, as this can be crushed with incorrect fitting of one of the studs.

[k.alle]

OK, then I have to ask what the benefit is with ARP head studs? Is it not reuseability ?
I'm not trying to be a smart *** here, I am really want to know.
The x-beam rods came with ARP and that I get because of the stress put on them.

But mains and head I'm not really sure about?

[Error404]

I agree, ARP head studs make more sense and I would use them regardless, with SQ or custom washers as Rusty says
I went for ARP main studs too, but they are not necessary for my engine.

If you are going for around 600hp I would use both.

IIRC you can lift the head upwards of 500hp on the OEM head bolts. Plus they are reuseable so i you have to remove the head once they have paid for themselves Vs OEM.

[Thuppu]

And like you knew, full torque specs with the ARP mains can lead to the need of line-honing, as it can deform the main caps. Well, standard bolts have been used in high power(+800hp) applications without problems.

[Error404]

And like you knew, full torque specs with the ARP mains can lead to the need of line-honing, as it can deform the main caps.

This.

My mains were out by 0.002mm after fitting ARP main studs, so under 1 thou. Not perfect, but I ran with them as oil clearance was still good
For perfect build you should align-hone

[k.alle]

OK, so ARP head studs seems to be the way to go according to you guys.

Im not aiming for any big numbers in that respect, it will be a Billet RS2 turbo with cams mapped on E85. It's the mahoosive torque Im after, so 400+ bhp.
And since Ill be running OEM pistons they will be the limit in the future in that regard.

[Error404]

Cool, so I would suggest ARP head studs & OEM mains

[k.alle]

Nice, that's what ill do then. Thanks for the help.

Does anyone know the part numbers for the OEM main stud gear?
Kate won't tell me..

[Thuppu]

You can just buy any M10 10.9 grade bolts for the mains, costs like 5 euros or so.

[k.alle]

Still need the dimensions, M10x?? and are they fully threaded or do they have a waist? If so how long is the waist?

[Thuppu]

I didn't remember the lenght, but I found it. Just basic M10x1,5x80 part threaded what you can find from any bolt shop, there is usually thread enough. Remember 10.9 grade though. Torque to 65Nm with motor oil.

[k.alle]

Allright, thanks Thuppu.

I'll buy both 12.9 & 10.9 and let the engine builder test if the 12.9 works without deforming the caps @ 80Nm. If it doesn't work they can fall back on standard 10.9 @ 65Nm.

Is it OK with allen head for this application? Im sorry for the stupid questions but I'm 100km from my spare engine that I haven't disassembled.

[EDIT]
Oh, how many is required?

[Error404]

Socket cap head is fine, a lot of 12.9s are socket cap anyway
Make sure you use the washers.

12 x main bolts

[k.alle]

I just bought these, a bit expensive but no where near ARP prices and hassle free:
http://cgi.ebay.de/ws/eBayISAPI.dll?...X:DERP:DE:1123

Will get som 10.9 at work also, better have some alternatives!