SS Head bolts

Player#3 · Apr 28, 2014

Hi,

With an iron cylnider block and an aluminium head what is the general opionion on using stainless steel head bolts. Three different metals in tight contact with each other seems like asking for trouble.
The original bolts are mild steel.

Are SS head bolts are good idea ?

Regards,
Sean

Matchless · Apr 28, 2014

The original bolts are not mild steel. They will either be EN 8 or En 16 or similar. The biggest problem I would have with the commonly available stainless head bolts, is they are made from 303 grade which is a fairly low tensile free cutting material. The same as used in A2 grade fastners. Colorado Norton Works sell ARP stainless bolts which I would imagine are of a high quality but make sure you use nickel or copper anti scuffing paste.
Martyn.

Hobot · Apr 28, 2014

My Peel had SS bolts from Rocky Point and withstood over rev event and HI heat playing with moderns for most an hour a go - so only thing bad that happened was the SS turned brown like one would see on SS headers. Still nicer to handle and see than factory issue. I used normal silvery anti-size on threads but not under the heads w/o issue of bind or corrosion. Re-used head bolts on 2nd Combat as discolored enough not to be noticed as not factory issue on her.

Matchless · Apr 28, 2014

Correction to my previous posting.
304 grade is used for A2 grade fastners.
Martyn.

acotrel · Apr 28, 2014

I think you will find that standard head bolts are about 90 ton tensile strength. There might be too much stretch in SS ones, and they might change when heated during operation, even at relatively low temperatures. There is usually a balance between martensite and austenite in most stressed steels. Also if you re-tension SS items several times, the effect of the grain structure could be uncertain. I think that a low alloy steel might be more stable in that sort of application. I wouldn't use SS bolts to hold a brake caliper, or plated low alloy steel ones. I always use button head hi-tensile button head bolts, and I give them a little spray with matt black paint to stop the rust. They are not so good in shear, however I can't think of anything better. Many years ago I lost a friend at Bathurst when the discs exploded off his bike at the end of Conrod Straight, and he ended up in the spectator area. - Take care.

RoadScholar · Apr 29, 2014

hobot said:
My Peel had SS bolts from Rocky Point and withstood over rev event and HI heat playing with moderns for most an hour a go - so only thing bad that happened was the SS turned brown like one would see on SS headers. Still nicer to handle and see than factory issue. I used normal silvery anti-size on threads but not under the heads w/o issue of bind or corrosion. Re-used head bolts on 2nd Combat as discolored enough not to be noticed as not factory issue on her.

Rocky Point uses 316 Stainless for its engine fasteners, they are made locally, and they are more than adequate for the application and have been in service for over 20 years with no reported failures. The down side is that they are more expensive then their OE type carbon steel counterparts, but they will not corrode/rust. The stainless fasteners don't stretch any more than the OE type, but any new head gasket installation should be followed up with re-torqueing several times, regardless of head bolt material, until the mating surfaces/gasket interface settles down.

B.Rad · Apr 29, 2014

Gidday All.
There is nothing wrong with stainless per se. to me the only advantage is cosmetic. if making the head bolts your self use 431 as a minimum, 630 is better. more than adequate. If made correctly especially the thread run out area, a very hot streety will not damage them. 316 obviously works, but those of a more pedantic nature or those seeking a higher tensile strength and fatigue resistance than 316, use 431 or 630. these commercial grades have a proven record . these are more than required, but even when used for racing will give peace of mind. En16 is not 90 ton, more like 55/60. Matchless has good advice especially lubricating the threads. matchless, please correct me if Iam wrong, but there is a big difference in composition and properties between En8 and EN16. Perhaps the English lads will wade in here . anyway 431 and 630 are very suitable steels with a proven usage as high tensile fasteners. and easily available too. Hope this helps Bradley

Matchless · Apr 29, 2014

Bradley,
431 is a good choice for bolts & spindles etc. I think, size for size it has a similar strength to a 10.9 grade bolt. I have made many wheel spindles out of this with no fear of breakage. Unlike the ones that some dealers sell made in 303. IMO not suitable at all.
The difference between EN8 & EN16 is the later has approx. twice the Manganese content & also contains Molybdenum. You are correct with 55/60 Tons tensile. EN8 is approx. 40 Tons.
Martyn.

john robert bould · Apr 29, 2014

303 is kind on taps/dies and is suitable for low stress items..carb studs etc ... i have a bar of ss that instanly work hardens ..OK for for any thing ,,if you can turn it :lol:

Lorenzo · Apr 30, 2014

when using stainless steel bolts and nuts on the engine, would you keep the same torque settings?

pete.v · Apr 30, 2014

Lorenzo said:
when using stainless steel bolts and nuts on the engine, would you keep the same torque settings?

I would never want to exceed the standard torque rating. Remember that any of these bolts, or stock for that matter, will be stronger than the soft alloy they are fastening. Through bolt with nut are one thing, but tightening into threads is another. Always use antisieze to prvent galling.

dennisgb · Apr 30, 2014

300 series of stainless steels are known as austenitic grades and are not hardenable by heat treatment. Some hardening can be obtained by mechanical work. I would guess that 300 series is not used for head bolts. The 400 series "martensitic" stainless steels such as 420 and 440 and others in the "martensitic" category can be hardened by heat treatment. I would guess that these would be the ones used for head bolts as the 300 series SS are very soft and would not be able to be torqued without breaking. We use 420 SS in plastic molds because the material can be hardened to the levels of tool steels and it does not corrode when water is used for cooling (which most molds have).

Lorenzo · May 1, 2014

pete.v said:
Lorenzo said:

when using stainless steel bolts and nuts on the engine, would you keep the same torque settings?

Click to expand...

I would never want to exceed the standard torque rating. Remember that any of these bolts, or stock for that matter, will be stronger than the soft alloy they are fastening. Through bolt with nut are one thing, but tightening into threads is another. Always use antisieze to prvent galling.

thanks..
what kind of antisieze would you suggest?

pete.v · May 1, 2014

Lorenzo said:
pete.v said:

Lorenzo said:

when using stainless steel bolts and nuts on the engine, would you keep the same torque settings?

Click to expand...

I would never want to exceed the standard torque rating. Remember that any of these bolts, or stock for that matter, will be stronger than the soft alloy they are fastening. Through bolt with nut are one thing, but tightening into threads is another. Always use antisieze to prevent galling.

Click to expand...

thanks..
what kind of antisieze would you suggest?

I don't think it matters so much as long as you use some. Your choice but I would think "high temp" might be advisable. They pretty much all are high temp but look for it on the label just the same.

This stuff is good to 1600F.
http://www.autozone.com/autozone/access ... 78722_0_0_

acotrel · May 1, 2014

I'd never fit stainless steel bits to an old British bike. If anyone has an eye for detail, it stands out and you know immediately that the bike is non-original and tricked up. If you are only using your bike to commute and need to stop it from rusting SS might be OK. If you care about originality .... ? I don't particularly like Velocettes, however a nut and bolt original Thruxton is to die for - fitting SS bits to something like that is sacrilege. It shows a complete lack of taste and sense of history. Then you have to ask - why own the bike ? I'm not a purist however there are some things I never do - this is one, and the other is fitting obviously Japanese parts to my Seeley Commando 850. I work actively to get rid of them, - there a still three or four minor items on the bike, and I am very conscious of them. These days I go to historic race events, and I see bikes such as the Molnar Manxes with cranked brake levers on them which are obviously modern - it doesn't help me get my nostalgia kick because I actually know what a 62 model manx used to look like. When you see the Honda drum brake in the front - bullshit ! Better to race and forget all about history. Even at Goodwood Revival a lot of the historic bikes are scrappy, and building them that way is often no cheaper.

Peter R · May 1, 2014

acotrel said:
I'd never fit stainless steel bits to an old British bike. If anyone has an eye for detail, it stands out and you know immediately that the bike is non-original and tricked up. If you are only using your bike to commute and need to stop it from rusting SS might be OK. If you care about originality .... ? I don't particularly like Velocettes, however a nut and bolt original Thruxton is to die for - fitting SS bits to something like that is sacrilege. It shows a complete lack of taste and sense of history. Then you have to ask - why own the bike ? I'm not a purist however there are some things I never do - this is one, and the other is fitting obviously Japanese parts to my Seeley Commando 850. I work actively to get rid of them, - there a still three or four minor items on the bike, and I am very conscious of them. These days I go to historic race events, and I see bikes such as the Molnar Manxes with cranked brake levers on them which are obviously modern - it doesn't help me get my nostalgia kick because I actually know what a 62 model manx used to look like. When you see the Honda drum brake in the front - bullshit ! Better to race and forget all about history. Even at Goodwood Revival a lot of the historic bikes are scrappy, and building them that way is often no cheaper.

Fitting sainless fasteners to old bikes should be lacking sense of taste or history ? or even sacrilege ? come on mr. Acotrel, get real.
My (unrestored) Commando has several stainless steel fasteners and brackets fitted . with the original cad/zinc plated parts the bike was looking very "second hand" .
I used the Commando often to commute to my work, and also has modern tires fitted (Avon roadriders), Is that Sacrilege too ?, no, in my opinion just a consession to practicallity.
I wouls say ,each to his own , but if we use our machines for serious riding instead of museum objects, concessions will have to e made here and there.
What about replacing screws with allen bolts ? the list can go on..
As historic racer, you may have seen Goldstars with ABSAF engines, Seeley frames etc , and not a single part that has ever come from the BSA factory.
Our Commando' s are today kept on the roads with replica parts from all over the planet. Originality ?
Motorcycles are intended for riding, not as ornaments in the living room.
Just my 2c worth..

acotrel · May 1, 2014

I don't have a problem with historic racing bikes which are replicas as long as they look right. What I have a problem with are guys who have really beautiful classic bikes and add bits which are obviously non original - that you can see when you stand 3 metres away. Some of the bikes that turn up to the Phillip Island meeting on Australia day are absolutely perfect, many more have bits fitted which destroy any notion of originality. I couldn't care what tyres you fit to your bike, however if the rear tyre on a fifties British bike looks like it is off a chopper - forget it.
We have historic racing in Australia which looks nothing like 'history'. That's OK, however why pretend ? - 'The best rules is no rules'.

DogT · May 1, 2014

I put SS bits on mine because I think it deserves it and I got tired of rusty looking bits. As far as originality, once it's painted or the decals replaced that's that. My concern is only that it 'looks' original and not like a crotch rocket. There's too many seals, gaskets and even chrome parts that are not 'original', what ever that means to someone. I doubt that there's 2 or 3 'original' Nortons out there and I wouldn't trust them. They're probably in museums. I realize some like the look of matte zinc but that can also be reproduced on SS with blasting. My 2c.

Hobot · May 1, 2014

Oh yeah there's a good number of orginal factory issued Commandos running, my Trixie Combat for one but for the tires and mirrors and rear sets. Works a treat till auto advance wears out but I've got spares so nothing to explain away while looking down shuffling your feet in shame.

kerinorton · May 1, 2014

Stainless steel is hard and when it breaks off [ and it will ] it is a bitch to drill out. I don't use stainless where strength is important. No problem painting the heads of the bolts with engine enamel to make them look better.

SS Head bolts

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