Crankcase and mounting hardware grade

danfr

danfr

VIP MEMBER
Joined
Oct 17, 2012
Messages
138
Country flag
Hey all, I need to purchase all the hardware to join my crankcases, front ISO and cradle mounts. What grade is the OEM hardware? Does grade 5 suffice or should I bump up to grade 8?

Has anyone used the stainless RGM hardware kit? I'm surprised they're selling a stainless kit but perhaps its a different alloy that I more appropriate for engine mounting.
 
danfr said:
Hey all, I need to purchase all the hardware to join my crankcases, front ISO and cradle mounts. What grade is the OEM hardware? Does grade 5 suffice or should I bump up to grade 8?

Has anyone used the stainless RGM hardware kit? I'm surprised they're selling a stainless kit but perhaps its a different alloy that I more appropriate for engine mounting.
Click to expand...
I'm not a metallurgist! According to McMaster-Carr, all 3/8" UNF tensile strength (psi) :

Stainless 316: 70,000
Stainless 8-18: 80,000
Grade 5 Steel: 120,000
Grade 8 Steel: 150,000

A bigger problem is getting the right length. With standard washers and nuts, for the front ISO the available bolts are too long or short. If using 4-1/4" for the bottom one and NyLock nut it's about right. The top one will work with a standard nut but it's only correct with 4-1/8". The rest are fine for standard washers and nuts at 4-1/4" but short for Nylock nuts.

The AN kits may be a little expensive, but everything is the right size, length, and strength. If 750 - 72/73 you need 13.1663 and 13.1810; if 850 - 73/74 you need 13.1663 and 13.1811; if MK3 you need 13.1664 and 13.1812

Since many use 8-18, to me Grade 5 is plenty.
 
Mine has all stainless. After 9,000 miles, the last 3 years have included winter riding, the hardware is still like new.

When I first got the bike @2,000 miles, it vibrated a fair bit. This was fixed by tightening up several of the bolts, especially the stainless engine to Iso bolts. So, maybe they release a bit after first installation? I've checked a few times since and they all remained tight.
 
marshg246 said:
I'm not a metallurgist! According to McMaster-Carr, all 3/8" UNF tensile strength (psi) :

Stainless 316: 70,000
Stainless 8-18: 80,000
Grade 5 Steel: 120,000
Grade 8 Steel: 150,000

A bigger problem is getting the right length. With standard washers and nuts, for the front ISO the available bolts are too long or short. If using 4-1/4" for the bottom one and NyLock nut it's about right. The top one will work with a standard nut but it's only correct with 4-1/8". The rest are fine for standard washers and nuts at 4-1/4" but short for Nylock nuts.

The AN kits may be a little expensive, but everything is the right size, length, and strength. If 750 - 72/73 you need 13.1663 and 13.1810; if 850 - 73/74 you need 13.1663 and 13.1811; if MK3 you need 13.1664 and 13.1812

Since many use 8-18, to me Grade 5 is plenty.
Click to expand...
I'm not familiar with those grade 5 and 8 UTS values which are different to what I am use to where grade 8 is 800MPa UTS. = 116,000 lbf/in2
 
danfr said:
Hey all, I need to purchase all the hardware to join my crankcases, front ISO and cradle mounts. What grade is the OEM hardware? Does grade 5 suffice or should I bump up to grade 8?

Has anyone used the stainless RGM hardware kit? I'm surprised they're selling a stainless kit but perhaps its a different alloy that I more appropriate for engine mounting.
Click to expand...
There is always the ARP kit from cNw. Overkill for some, but surely the best there is.
 
The factory apparently changed to high tensile fasteners (06.3211/2/3) from 207776 during 1972.
 
The ARP hardware would be amazing, but I have a budget to stick to.

RGM motors sells the high tensile fasteners (06.3211/2/3) which would be the sensible way to go. However, I went with their stainless kit as it’s more comprehensive and matches my stainless barrel and head hardware.
 
danfr said:
The ARP hardware would be amazing, but I have a budget to stick to.

RGM motors sells the high tensile fasteners (06.3211/2/3) which would be the sensible way to go. However, I went with their stainless kit as it’s more comprehensive and matches my stainless barrel and head hardware.
Click to expand...
You asked about grades etc, so did you get that info on the RGM kit ?
 
danfr said:
The ARP hardware would be amazing, but I have a budget to stick to.

RGM motors sells the high tensile fasteners (06.3211/2/3) which would be the sensible way to go. However, I went with their stainless kit as it’s more comprehensive and matches my stainless barrel and head hardware.
Click to expand...
Make sure you use an Anti-seize...
 
danfr said:
Hey all, I need to purchase all the hardware to join my crankcases, front ISO and cradle mounts. What grade is the OEM hardware? Does grade 5 suffice or should I bump up to grade 8?

Has anyone used the stainless RGM hardware kit? I'm surprised they're selling a stainless kit but perhaps its a different alloy that I more appropriate for engine mounting.
Click to expand...
Don't over worry it. I use stainless. Some of them are ARP, but not all. I use a stainless anti-seize on assembly. Race bike, rigid mount.
 
SteveA said:
Don't over worry it. I use stainless. Some of them are ARP, but not all. I use a stainless anti-seize on assembly. Race bike, rigid mount.
Click to expand...
You have a track master frame? Would love to see some photos of your race bike.

Thanks. Ya, I’ll keep an eye on them and retorque a few times after assembly. Anti seize of course.
 
Because of a previous experience where the bottom bolt broke, I replaced them all with Grade 8 plated bolts and nylon locking nuts. I sourced them from McMaster Carr. 15K miles and still tight.
 
Deets55 said:
Because of a previous experience where the bottom bolt broke, I replaced them all with Grade 8 plated bolts and nylon locking nuts. I sourced them from McMaster Carr. 15K miles and still tight.
Click to expand...
I had the bottom bolt bore machined out to accept a larger 3/8 bolt as there was some previous wear from a loose bolt. Perhaps your bolt came loose as well and broke?
 
danfr said:
I had the bottom bolt bore machined out to accept a larger 3/8 bolt as there was some previous wear from a loose bolt. Perhaps your bolt came loose as well and broke?
Click to expand...

I believe it was the 3/8" bolt seeing how I have a MKIII. Funny part was about six months later I was at a Norton rally and there was another bike there with the same issue. Bolt napped right at the nut, parts were laying under the bike. I bet the cause was the bolt getting loose. Was a PITA getting a new bolt in without lowering the engine because the bolt head would get caught on the frame.
I just figured when I had the engine out and apart for a rebuild I would go with Grade 8 where ever I could.
 

Similar threads

joe czech
  • Locked
(engine) exhaust mounting hardware - flared adapter for header pipe - ???
2
Replies
20
Views
3,500
river700
river700
A
1967 G15CS rear fender mounting hardware
Replies
8
Views
2,712
APRRSV
A
Back
Top