ARP Cylinder Head Studs and Washers

[RichardHawkins]

Has anyone fitted these studs?

I chose them because I thought they were better than the original bolt and marginally cheaper.

A previous owner must have been a bit of a strong man, as the majority of my head bolts have been stretched. Having noticed these stretched bolts I am replacing most of the fasteners on the car, just in case they have also been overloaded.

The ARP studs are a tight fit thought the head. They can be screwed in but are binding in the head as I do so. Basically the bolt holes in the head do not align correctly with the block, also the holes in the head are not quite square with the head surface.

Has anyone else encountered this problem, and what was your solution?

I also have a question about the head bolt washers. I didn't notice until after I had cleaned them, but two of them have groves machined in them. Where do they fit?

Richard Hawkins

[types26/36]

I also have a question about the head bolt washers. I didn't notice until after I had cleaned them, but two of them have groves machined in them. Where do they fit?Richard Hawkins

Bolts 7 & 8 have the "special washers"

[RichardHawkins]

Brian,

Thanks for the help and rapid response.

Richard Hawkins

[rgh0]

The special washers are to provide clearance on the cam bearing caps so they need to be aligned properly when tightened.

The head bolt holes close up overtime near the top so run a suitable drill through them to open them up so the studs can turn with a little clearance

I have never noticed any problem with head to block bolt alignment or head bolt holes not square with the head and block. But there is normally about 1 mm of movement possible in the head horizontally with the bolts in place and not torqued down. This clearance I guess would take up any small misalignment.

cheers
Rohan

[RichardHawkins]

Rohan,

Thanks for the help, the ARP studs are a nominal 7/16" diameter, and are parallel, unlike the original bolts which are wasted. The holes in the head are stepped, 29/64" at the top, and 7/16" at the bottom. I have opened out the holes to 11.5mm at he bottom, but still have the studs binding in the head. To have the same clearance as the original bolts I think I might need 12mm holes. Do you have any experience of how large these holes can be safely drilled to?

Alternatively, I could turn down the studs, any thoughts?

Richard Hawkins

[rgh0]

HI Richard
I will check out a few things on a spare head and block and set of studs and get back to you tonight

cheers
Rohan

[bill308]

Does anyone have an ARP part number for the block to head studs?

My new block will be alloy, so studs are preferable to bolts.

I'm of the opinion that coating the shank (non threaded portion) of the studs and corresponding cylinder head holes with a good anti seize compound will retard corrosion and facilitate later removal. Any down side to this practice?

Which thread locker is recommended for block retention?

Bill

[rgh0]

The ARP studs I got through Burtons have two numbers on the pack. The washers will also need the flats ground on a couple to clear the two bearing caps where this is required as there are all full circular

part no 20001356 - this may be the ARP number
and ARPHD02 - this may be the Burtons number

The holes at the bottom of my spare heads are all around 11.5 mm diameter
On a couple of my spare heads, where there is some head bolt recession, the holes are smaller at the top and the studs bind in them. In one the reduced shank head bolts look like they had to be screwed out and have formed thread marks in the top section when removed.

I have attached a photo of the 3 types of spare bolts I have:

The ARP studs are an 11.05 mm shank with 10.9 mm threaded ends
The spare "Straight" shank bolts I have come with a 10.9 mm thread and top 25mm but the main shank is 9.8mm
The spare "Reduced" shank bolts I have come with 10.9 mm thread and top 10mm but the main shank is 8.65mm
.
I have also seen "Straight" shank bolts that would be 10.9mm diameter along their entire length

I have also attached a photo of a head sectioned through the bolt holes showing the amount of metal around them. Looks like no problems enlarging the holes if needed but you need to be careful you don't upset the alignment on the head to block when you do it by introducing excessive clearance

cheers
Rohan

[rgh0]

Rohan,

Thanks for the help, the ARP studs are a nominal 7/16" diameter, and are parallel, unlike the original bolts which are wasted. The holes in the head are stepped, 29/64" at the top, and 7/16" at the bottom. I have opened out the holes to 11.5mm at he bottom, but still have the studs binding in the head. To have the same clearance as the original bolts I think I might need 12mm holes. Do you have any experience of how large these holes can be safely drilled to?

Alternatively, I could turn down the studs, any thoughts?

Richard Hawkins

Richard
It sounds like someone had previously drilled out the top section of your bolt holes for clearance

cheers
Rohan

[RichardHawkins]

Rohan,

Thanks again for your help.

I also bought my studs from Burton. The box has

ARPHD02, which I also think is the Burton number.

Burton, in turn, buy ARP products from Kent Cams, and the other number on the box,

HSL68, which I think the Kent Cams number as it also appears in Kent's catalogue.

Bill,

These ARP studs have a 3/16" hex socket in the top of the stud to ease installation and removal. I think I remember something from the ARP web site that makes me think they would not recommend using an adhesive to retain the studs. ARP supply their own (moly?) lubricant with the studs.

As you are in the USA, you might be able to get advice direct from ARP rather than through several intermediate suppliers.

Richard Hawkins

[bill308]

Thanks guys.

I sent an email to ARP asking if they could provide the correct part numbers. I'll let you know what happens.

Bill

[Jentwistle3]

Is that really a Lotus head?

[rgh0]

Yes - section through the bolt holes and placed on the bed of a photocopier. I have a similar section through the ports I think I have posted previously

cheers
Rohan