Improved head bolts

The CNC machine work on those bolts is very impressive.

ashman said:

After 48+ years (1974 850 Commando motor) I am still using my original head bolts with copper head gaskets, I only retorque at 500 miles and leave it alone after that and have never had a blown head gasket and only once I had to retorque the head after getting a slight seep and it stopped, my last head removal I forgot to anneal the copper gasket and had the head torqued down before I remembered so let it be, but I had sprayed copper gasket sealant on it that was well over 15 years now (only retorqued after first 500 miles) and the head hasn't seeped or been retorqued since with over 35k miles on it, I have never had a copper head gasket blow completely out but had blown a fiber head gasket completely out that came with my Norton from the factory.
In fact all my motor studs and nuts are still original except the front centre barrel stud and nut and all my timing case and outer gear box case had the screws replaced with allen head bolts back in 1978 and are still using the same bolts today.
Maybe if using alloy barrels then maybe I would use the waste head bolts, but my head has been shaved and had major port work done but still running the original valves and pushrods with a 2S cam grind and 40thu over size flat top Hepilite pistons and balanced crank, been built this way since 1982.

Ashley
View attachment 116982

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Where do I get the decal?

concours said:

Where do I get the decal?View attachment 117216

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To be honest they been on there so long I can't remember where I got then from there are 2 the same one for each side of the tank on the other side I had paint lifting around the fuel cap so that is where the other side decal is covering the lifting paint, I could have gotten them from a swap meet over 20+ years ago, they look great and stopped the paint lifting, the paint on the tank has a lot of battle wounds/scares, there are chips and a few small dents at the front of the tank and scratches here and there, it was painted 2 years after the great fire of 82 so the paint job is 40 years old and still looks good for the years it's been on the road.

Ashley

jseng1 said:

The JSM bolts are triangular because that cross section shape is stronger than just reducing a cylindrical bolt to a smaller diameter. The triangular shape still has the original diameter at the tips of the triangles and so it resists twisting more than a bolt which is simply a smaller diameter. The triangle shape also keeps everything centered in the round bolt holes and that allows for reduced shank studs.

Reduced shank studs (triangular)

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What is the threaded length of the three studs, head end?

marshg246 said:

What is the threaded length of the three studs, head end?

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A little more than 1/2" length. See this vid for timesert installation.

jseng1 said:

A little more than 1/2" length. See this vid for timesert installation.

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Good video, but it should be noted that if the studs do not end up absolutely perpendicular to the head in all directions and in the correct locations, the head won't go on. A milling machine and some care makes that easy, a good drill press and a LOT of careful setup probably will work fine. Hand drilling will ruin a head!

I went through the misery of having a "professional" machine shop do it and they got the studs off by about 2 degrees - then after a bunch of begging, I got Jim Comstock to fit it into his schedule and fix it.

Here's how a head in decent shape can be prevented from having the need to be repaired: https://gregmarsh.com/MC/Norton/Info/HeadStudStudy.aspx

marshg246 said:

Good video, but it should be noted that if the studs do not end up absolutely perpendicular to the head in all directions and in the correct locations, the head won't go on. A milling machine and some care makes that easy, a good drill press and a LOT of careful setup probably will work fine. Hand drilling will ruin a head!

I went through the misery of having a "professional" machine shop do it and they got the studs off by about 2 degrees - then after a bunch of begging, I got Jim Comstock for fit it into his schedule and fix it.

Here's how a head in decent shape can be prevented from having the need to be repaired: https://gregmarsh.com/MC/Norton/Info/HeadStudStudy.aspx

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Do you carry the British Fasteners studs? So it looks like the stud holes in the cylinders may need some CAREFULL widening...perhaps a 64th over.

The same effect as achieved using waisted bolts/studs can be had by using longer, standard diameter shank, bolts/studs with steel spacers under the bolt head or nut.

seattle##gs said:

Do you carry the British Fasteners studs? So it looks like the stud holes in the cylinders may need some CAREFULL widening...perhaps a 64th over.

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I don't, he doesn't have dealer accounts so I'm just a customer.

No widening required.

Some heads have the holes more than deep enough for the longer threads but aren't threaded all the way, so I run a bottoming tap in them to make the threads deep enough - that's the only modification that is sometimes needed to the head or cylinders.

The original british 3/8" studs have a tendency to pull out so replacing them with a high quality stud with brit thread is a waste of time and money (I used to provide them but quit). You need a timesert (preferred) or helicoil in there because the steel insert has larger diameter threads and more strength to avoid stripping out the alum threads. The heavy US 16 TPI in the alum is the best choice. Its also the best choice for the head to cylinder fasterers as Maney provided because the problem is stripping out the alum threads (not clamping pressure which is fine as I have seen no leaks and I also use pliobond). Note that the US 16 tpi also works fine bolting the cylinders to the cases and it would be a mistake to put finer threads in there.

marshg246 said:

I don't, he doesn't have dealer accounts so I'm just a customer.

No widening required.

Some heads have the holes more than deep enough for the longer threads but aren't threaded all the way, so I run a bottoming tap in them to make the threads deep enough - that's the only modification that is sometimes needed to the head or cylinders.

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Greg, do you know the tensile strength of the material that British Tools and Fasteners employ? I am on the alert each time a company claims to use "stainless steel", which may have lots of meanings.
Consumer grades of AISI 304 or 316 are not usable for cylinder head studs and bolts. Unless a MDS (Material Data Sheet) is presented, I would caution anyone to use their studs in a highly stressed area.

Other than lack of a material specification, their offering is interesting.

- Knut

mdt-son said:

Greg, do you know the tensile strength of the material that British Tools and Fasteners employ? I am on the alert each time a company claims to use "stainless steel", which may have lots of meanings.
Consumer grades of AISI 304 or 316 are not usable for cylinder head studs and bolts. Unless a MDS (Material Data Sheet) is presented, I would caution anyone to use their studs in a highly stressed area.

Other than lack of material specification, their offering is interesting.

- Knut

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Agreed - I looked carefully into ARP's SS offerings before fitting them.
Yes - SS can be weak, but not always.
Cheers

robs ss said:

Agreed - I looked carefully into ARP's SS offerings before fitting them.
Yes - SS can be weak, but not always.
Cheers

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Rob,
That's true. ARP's best performing material is a carbon steel, not stainless. The lower grades are alloyed steel of various types.

SS is a collective term which has a meaning in the construction sector and for outfitting purposes, where lasting finish is paramount. In structural / mechanical applications, precise declarations are called for however.

Greg's investigation didn't mention quality of threads at the samples he investigated. For highly stressed dynamic applications, threads need to be rolled. Threads fabricated by turning are frequently far from smooth, having peels and crevices on a small scale.
These are perfect fracture initiators! So, small diameter threads need to be rolled, while larger diameter threads _can_ be formed by cutting (the lower stress level will slow down or inhibit crack propagation).

This is a recommendation we translate into action at the engine's top end by fitting ARP or another brand high tensile bolts with rolled threads, combined with thread inserts (TimeSert or Helicoil).

- Knut

mdt-son said:

Greg, do you know the tensile strength of the material that British Tools and Fasteners employ? I am on the alert each time a company claims to use "stainless steel", which may have lots of meanings.
Consumer grades of AISI 304 or 316 are not usable for cylinder head studs and bolts. Unless a MDS (Material Data Sheet) is presented, I would caution anyone to use their studs in a highly stressed area.

Other than lack of a material specification, their offering is interesting.

- Knut

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No clue. However, considering that originals of the subject studs can pull out, the current AN version (made to the drawings) are almost guaranteed to pull out, and that I've never had any trouble with longer thread and better fitting threads, it is what I will continue to do.

In a perfect world we'd all be machinists and have a good milling machine and lathe so the heads could be corrected as Jim Comstock does:

This is an interesting study he did on the various thread repair inserts:

BTW, do you know the tensile strength of the original studs or the AN replacements?

mdt-son said:

Rob,

Greg's investigation didn't mention quality of threads at the samples he investigated. For highly stressed dynamic applications, threads need to be rolled. Threads fabricated by turning are frequently far from smooth, having peels and crevices on a small scale.
These are perfect fracture initiators! So, small diameter threads need to be rolled, while larger diameter threads _can_ be formed by cutting (the lower stress level will slow down or inhibit crack propagation).


- Knut

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I did talk in Lay terms about that very subject. The visual quality and fit in the head of both the RGM and British Fasteners threads are highly superior to the original and current AN studs. A large percentage of the RGM studs have the threads rolled/cut at a slight angle to the stud. I could find no fault with any of the British Fasteners studs.

Also, I asked and they replied. The British Fasteners studs are A2 (that's all he said).

mdt-son said:

Greg, do you know the tensile strength of the material that British Tools and Fasteners employ? I am on the alert each time a company claims to use "stainless steel", which may have lots of meanings.
Consumer grades of AISI 304 or 316 are not usable for cylinder head studs and bolts. Unless a MDS (Material Data Sheet) is presented, I would caution anyone to use their studs in a highly stressed area.

Other than lack of a material specification, their offering is interesting.

- Knut

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Here's what RGM says about their studs: https://www.rgmnorton.co.uk/buy/cylinder-head-to-barrel-stud-3-8-stainless_156.htm

marshg246 said:

Here's what RGM says about their studs: https://www.rgmnorton.co.uk/buy/cylinder-head-to-barrel-stud-3-8-stainless_156.htm

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It's a pity they're out of stock.

The JSM stud threaded portion is a fair bit- around 1/4" - longer that the hole they're going in.
Who's going to suggest drilling the holes deeper?

There is a problem with the test in the video. The big sert is guarrenteed to have higher strength than the smaller standard time sert for the same reason that larger diameter big easy locks can take more torque than smaller serts or helicoils. The larger the OD on the sert/helicoil the more pressure it will take before it fails. But in the video test the big sert shows less strength than the smaller standard timesert. This is wrong/backwards and it makes the entire test suspect. This probably happened because the cast head had soft spots.

To make an accurate test/comparison of inserts and helicoils you need to use a piece of alum that hasn't been heated up to different temps in different areas throughout its life the way a cylinder head gets heated. Cast alum is a poor choice. For accuracy you need a piece of fresh alum plate that has consistant strength throughout the material. When you make a test this way you will find that the larger diameter sert/helicoil has the most strength (assuming its the same threads per inch). Its the same as using a bigger stronger bolt.

Note that at the end of the video Comstock says that the larger inserts "will hold considerably more than the small common insert". But his test contradicts this because the big sert failed before the smaller timesert (soft spot in the cast alum?).

But you can't go too big or you run out of room and aluminum.

B+Bogus said:

It's a pity they're out of stock.

The JSM stud threaded portion is a fair bit- around 1/4" - longer that the hole they're going in.
Who's going to suggest drilling the holes deeper?

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The holes are plenty deep on all I've checked to handle 9/16" of threads - some need a bottoming tap to take the threads deeper but most are deep enough for the longer stud threaded portion. AFAIK, the JSM studs require thread inserts (I've never done them).

cNw also has a head fixing ARP kit. The three studs require thread inserts there too.

jseng1 said:

There is a problem with the test in the video. The big sert is guarrenteed to have higher strength than the smaller standard time sert for the same reason that the big easy locks can take more torque than smaller serts or helicoils. The larger the OD on the sert/helicoil the more pressure it will take before it fails. But in the video test the big sert shows less strength than the smaller standard timesert. This is wrong/backwards and it makes the entire test suspect. This probably happened because the cast head had soft spots.

To make an accurate test/comparison of inserts and helicoils you need to use a piece of alum that hasn't been heated up to different temps in different areas throughout its life the way a cylinder head gets heated. Cast alum is a poor choice. For accuracy you need a piece of fresh alum plate that has consistant strength throughout the material. When you make a test this way you will find that the larger diameter sert/helicoil has the most strength (assuming its the same threads per inch). Its the same as using a bigger stronger bolt.

Note that at the end of the video Comstock says that the larger inserts "will hold considerably more than the small common insert",

The problem then is if you get to big then you run out of room and aluminum.

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No engineering disagreement, but his method is using an actual head in a closer to real-world test with a Norton head. It's clear that any of the inserts would go MUCH higher in a perfect environment and, IMHO, the strength of the metal of that head was the limiting factor.

The studs pulled at ~35 ft. lbs. and according to service release N3/68 35 ft. lbs. should be used!