Thread type model 8

[Janet]

ps I have a Stannah stairlift for sale

Advertising id not permitted on the forum, even if it is a vehicle.

[gareth55]

Hi Everyone, this is my first post on the forum.
I also have a 1960 Model 8 and am trying to re fit the hairpin valve springs, after much frustration using a conventional coil spring compressor and not succeeding i bought from the club parts scheme a "single" hairpin spring compressor.It arrived this week but i have just tried to use it for the first time, but it did not come any any bolts to fix it to the cylinder head. I have looked through by bolt stock, but can find anything to fit the threads in the cylinder head. The actual head bolts are too long to get the spring compressor fixed into the head. Thus my question is what are the threads in the cylinder head are these also BSF. This seems a funny choice of thread for an aluminium casting, but i guess stranger things have happened.
Any suggestions?
Thanks in anticipation of your help.
PS it would have been nicer if the club parts scheme had also supplied short bolts to go with the spring compressor.
Cheers Gareth

[Janet]

Hello Gareth. Welcome to the forum. I don't know all the technical stuff but I have learned from those who do that AMC did put BSF threads into aluminium.

[cbranni]

Hi Gareth .........and welcome, I have never used a hairpin spring compressor but in the manual it shows the tool being held by hand I think.....and says the following

"to operate this tool apply the top end of the valve to it's groove in the top cap, then insert a short rod (one of the rocker box bolts is ideal) through the holes in this tool and the valve spring coils and pull outwards and upwards until the ends of the prongs of the spring can be rested on the seat, then press down with the fingers.
withdraw the bolt or rod when the compressor lies against the head, retaining pressure with the fingers until the bolt as been withdrawn and the tool removed, when the spring can be easily pushed down to its location with the prongs lying flat on the seat"

Clear as mud.................I just use my fingers

Colin

PS Janet is correct AMC used BSF in alloy but not Norton they used BSW

[Groily]

It is tempting to go BSW (or UNC even) on some of these things, and of course many factories might have used coarser threads than BSF into aluminium. However, where smaller sizes are insisted upon for whatever manufacturing reason, coarse threads have the strength disadvantage that the minor diameters - ie the core diameter at the bottom of the threads - are rather reduced, whereas using BSF you get a bit more metal in the middle.
As a spotty youth I thought I was also taught never to use fine threads into ali, the trick being to make sure the fastener was of a decent diameter suitable for a coarse thread in the first place.
I suppose it all depends on what we mean by 'coarse'. I call BSC and UNF 'fine', BSF and standard metric sizes 'medium', and BSW and UNC 'coarse'.
I wonder how many times the problem of stripped threads various on fork sliders has been mentioned here - a lot, anyway.
And only AMC, as far as I can see, ever thought to use 2BA on crankcases (to attach twin timing covers). That, I think, was taking the mickey. OK when new and before going through the hands of the ham-fisted, but they are too fine for that job despite being successfully used into alloy on electrical components. Sometimes one has to wonder whether any thought was ever given to what would happen over time . . . . but even if it was, I don't suppose the factory was thinking of us in our sheds 60 or more years later!

[SPRIDDLER]

Welcome, Gareth
The tool Part no. 018276 is shown in use here, page 27
http://archives.jampot.dk/book/Workshop ... dition.pdf

....although from your mention of suitable bolts to fix it onto the aluminium rocker box I suspect that you have the half moon tool, Part no. 014605, which is shown in use on page 26.
The cheaper hand held tool 018276 (see photo on Club Spares page) is used more as a valve spring lever (like a beer bottle opener) than a spring compressor and is a doddle to use, and simple to make at home, (but I guess you didn't want to know that), although as Colin mentioned not strictly necessary if you have a strong wrist as the hair springs can be fitted quite easily without a tool.

BTW - To answer your original question, from memory the rocker box bolt threads are 5/16" BSF

[Ozmadman]

Welcome, Gareth
as Colin mentioned not strictly necessary if you have a strong wrist as the hair springs can be fitted quite easily without a tool.

That's what I did I fitted mine by hand with a bit of perseverance and effort and I am only a shrimp!!

[56G80S]

No way on earth I could fit those hairsprings by hand only.

You lot are just showing off.

But the cheap tool works fine.

Johnny B