arp 11th bolt size?
Turbo Mini Forums

Just had email from minispares saying this is not in stock, bit of a pain as the block is at the machinist and would have rather given him the bolt than just a size. Can anyone 100% tell me the size of this as a search brings up 5/16 and m8 with the odd 3/8 chucked in lol.
Cheers

all ARP sets ive bought use a short atandard type stud ,therfore 3/8unc

Edited by fastcarl on 29th Oct, 2009.

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definatly a special bolt...
"A true Cooper S engine has 10 studs and one specially designed bolt. The ARP version of the stud is a 12 point design that matches the head stud kits (Which come in either 9 or 11 stud.) Best of all, the ARP bolt cost less than the standard item! "
Shame they dont have it eh! Sure its smaller than 3/8 though.
A search recons the rocker box wont fit with regular studs?

I,v always used regular studs, but you will need to relieve the flange on the rocker cover to allow the nut to fit.
Thats probably why the Cooper S type is 5/16

My ARP kit uses the same stud as all the other short ones.

My ARP kit came with a 5/16 bolt and 11 3/8 studs so I could make my own choice, thought all kits were like this

Paul

I seriously doubt it!

It might well be a 5/16 UNC bolt.

mines 3/8 unc for the usual 9 and 5/16 unc for the extra 2.

Thanks for replies, still no clearer though :) shall i just go with 3/8? and not bother with the arp or just leave as 9 stud. Confused.com

What are the holes in the block? Use that!

If you've got no holes, why not drill 5/16UNC then you can easily go to 3/8UNC at a later date...

As Vegard says.

If you use the 5/16 bolt then
1) dont torque it up beyond 40lbs ft
2) you wont need to relieve the rocker cover.

Even if you use the 3/8 size, because the drilling in the block is shallower its not a good idea to use more torque.
I have got away with 50/60 ft lbs but you could ruin the block.

Bolt 10 and 11 should not be torqued to more than 25lbs/ft. A 5/16 one must not be.

As I understand it, it is the one at the water pump end that is most important not to overtorque, as the block is hollow beneath so there is potential to distort the deck. This does make sense when you look at a block.

I agree with the principle Tom, but the block cannot distort too easily when it is clamped up to the head, surely. I always thought the greater risk was pulling the thread out of the block and taking enough with it to ruin it?.

Anyone who torques these bolts/studs beyond the above recomendations is on their own, including myself !.

Standard Cooper S uses an extra 3/8 unc short stud at the clutch end and short 5/16 unc bolt at the thermostat end (I have two in my hand as I type this - let me know if you want one !).

To the best of my knowledge, the stud is torqued to 40 lbft and the bolt is torqued to no more than 25 lbft, whereas the remainder of the 9 studs are torqued to 50-55 lbs depending on what the application is.

On the van, I'm not using the 5/16 unc bolt at the thermostat end but have instead drilled my block and MPi head to accept another short 3/8 unc stud - that now makes 7 short studs and 4 long ones. The extra two studs at each end of the head require the rocker cover to be relieved / cut out to give clearance for the nuts. Not too much though otherwise the gasket will leak.

The MPi head was straightforward enough to drill the extra two holes but I entrusted this bit to a pro as he had a pukka coolant fed pillar drill.

Notwithstanding the normal torque, I have always used 60 lbft on all my 3/8 unc head studs, including the thermostat end on the van, no exception, never a problem.

I know Stuart Wright also uses 60 lbft on his blue strip car as his old man assured me when he saw me at the IMM in August.

I agree with Tadge, it's down to the individual at the end of the day.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

Excellent, all the info anyone could possibly expect. Think i,ll probably go 3/8 as i have loads of studs and keep the tourqe low.
Cheers :)