camshaft locating bolt

[Steve kay]

   
Removal of the block allowed immediate access to the square headed cam shaft locating bolt. This turned out to be little more than finger tight. There has been much discussion of replacement and improvement of the bolt and the location it provides, for engines undergoing work. A basic response to a floppy thread would be helicoil replacement, but not at all a good idea for an assembled engine in the car. So, what response is advised? If the bolt's principal purpose is location, how strong a connection must it provide?  Would ptfe tape to minimise oil leakage, and possibly some loctite or similar to prevent movement be sufficient? Many thanks in advance.

[Ian Williams]

Drill the thread out 5/6", tap the cam shaft bush and install a stud with a Dowty washer under the nut, problem solved and it wont leak!

[Steve kay]

As well as emailing and contributing to the forum, Sevenists are very good at talking. Not just in the paddock at Shelsley, Loton Park or certain Lawns, but on the old fashioned telephone. So many thanks to those who have spoken to me, and whose advise was unanimous; don't worry about it. The bolt's purpose is location, rather than structural or mechanical. The square head will stop it coming loose, keep it secure with loctite and oil tight with a copper or Dowty washer. Not quite sure if the machine will be running again by the weekend, but there seem to be two dozen Sevens entered to  ascend a hill so much to look forward to.

[Colin Wilks]

I would not reuse the square headed bolt (the thread of which looks past its best) but make up a replacement from a new hex or cap head. Fairly easy to nip up if needed, or you could drill it and wire it. This would mean that if it starts leaking oil and you decide to follow Ian's advice, at least you can get the camshaft out without having to lift the block again.

[SneezerUSA]

My original bolt was wobbly and allowed the bushing to move forward along with the camshaft. Destroyed the fiber gear on the dynamo. I redrilled the hole both in the block and in the bushing. Tapped both and installed an Allen head bolt. Worked for me.

[AustinWood]

I agree with the use of hex head and I also tap the bush to 5/16 BSF too. This holds it much more firmly.
I've never seen a fibre gear on an Austin 7??

[Ruairidh Dunford]

I throw the square headed bolt away, tap 5/16 bsf through the crankcase and into the bush, then fit a bolt with a Dowty washer.

[Ruairidh Dunford]

The only fibre gear I am aware of is inside a magneto, sometimes...

[Hedd_Jones]

I've made a 5/16 BSF Cap head bolt into a direct replacement for the square headed abomination. Made it in the pillar drill with a file. No lathe at home. I also removed the square headed abomination without taking the block off.

Had I have taken the block off, Ian and Ruairidhs suggestion is best way by far. Saw it done on a Special I had, very good idea. Just make sure the bolt doesn't bottom out on the cam and nip it tight (don't ask how I know about that one LOL).

[dickie65]

If your peg bolt is loose or worn it will allow the camshaft to move fore and aft and get a bit too close to the big ends if very bad.
I use a new peg bolt to locate the bush and have a bolt threaded into the side of the bush from the left hand side of the crankcase. I have had no problems from this area for the last 20 years or so. Lockite and Dowty washer stop 60 Psi oil escaping.