Jump to content

BMC 1.5 crankshaft pulley bolt.


GBW

Featured Posts

Behind the crankshaft pulley bolt is a substantial hardened washer. If you can harden the centre of your new pulley ( assuming it is steel ) then you could leave this washer out which will give you around 6mm more thread length.

Link to comment
Share on other sites

The mystery deepens! (and my frustration increases).

The bolt from MG owners Club does not want to start.  It is 5/8" X 16 tpi.

It is very difficult to gauge an internal thread without a plug thread gauge.

However.  On the refurbished engine I have threaded into the end of the crankshaft a piece of 5/8" diameter soft HDPE.  

This has created a measurable thread on it.

It is 18tpi!  I.e., 5/8" UNF.

The remains of the bolt from the installed engine measure 16 tpi.

 

The boat is currently at Ilfracombe awaiting the fix.  

The original mod (by me) was to create a boss over which the Jabsco and alternator drive pulleys fitted and which had a threaded spigot on the end.

For some inexplicable reason, the whole lot unscrewed leaving the engine without seawater cooling.  (In the middle of Bridgewater Bay with a fast ebb and 49 metres under the keel is not a comfortable experience).

 

I think I will drill through the boss and make two bolts, one UNF and one UNS and hope one of them will serve.

 

Many thanks again to all.

 

The problem with old engines is that you don't know the history.

Link to comment
Share on other sites

If the crankshaft thread is mangled,then Id suggest you convert to an oversized thread like 3/4x 16 ,or maybe 3/4x18..(depending on whats there.).....as the motor is in pieces ,Id suggest the new thread is done in a lathe,to maintain factory alignment and fit..

Link to comment
Share on other sites

14 minutes ago, Cheshire cat said:

The MGB was never fitted with a 1.5 engine, only 1.8.

 

The MGA was fitted with a 1.5 but the crankshaft bolt has a dog on it for a starter handle. Not much use in a boat engine room!

 

 

You are assuming that the petrol engines used the same parts as the diesels, not confirmed at all. BMC were beggars for making changes to nut and bolt sizes at a whim, because the machined most of them themselves and could.

Link to comment
Share on other sites

I was merely pointing out that the bolt the OP has purchased is for a 1.8 B series and yes, of course petrol.

 

I'm scratching my head trying to think of a diesel car of that era. The Austin Cambridge was one but I think it may have had a Perkins diesel. 

Edited by Cheshire cat
to correct a word
Link to comment
Share on other sites

5 minutes ago, Cheshire cat said:

I was merely pointing out that the bolt the OP has purchased is for a 1.8 B series and yes, of course petrol.

 

I'm scratching my head trying to think of a diesel car of that era. The Austin Cambridge was one but I think it may have had a Perkins diesel. 

Austin Cambridge car, Austin J2 van and others used the 1.5D engine. There is also a tractor derivative.

 

1.8D engine was for the Sherpa van, a totally different engine with some common parts with the 1.5D.

Edited by Tracy D'arth
Link to comment
Share on other sites

4 minutes ago, Cheshire cat said:

I was merely pointing out that the bolt the OP has purchased is for a 1.8 B series and yes, of course petrol.

 

I'm scratching my head trying to think of a diesel car of that era. The Austin Cambridge was one but I think it may have had a Perkins diesel. 

 

Yes, the A60 and not Perkins, a BMC and I think it was a 1.5D. Also, the J4 and EA vans, although I think the EA version was inclined.

 

I also could not understand why the OP was looking at petrol 1.8 parts for a 1.5 diesel and why he seemed to looking for a die for a unified special thread that by its name says it will be non-standard.

Link to comment
Share on other sites

5 hours ago, Tracy D'arth said:

Austin Cambridge car, Austin J2 van and others used the 1.5D engine. There is also a tractor derivative.

 

1.8D engine was for the Sherpa van, a totally different engine with some common parts with the 1.5D.

 

When I first started work a colleague had an Austin Cambridge 1.5 diesel 

 

I used to tease him by saying that it would need a stop calendar to measure the 0-60mph time. 😂🤣

Link to comment
Share on other sites

9 hours ago, john.k said:

It seems from the text,that the OP is sideloading the threaded retainer with belt load..........if so ,this isnt recommended .

Not really.  The three pulleys are locked together by dowels (as explained) and sit snugly on a boss with appropriate diameters.  The bolt pulls the lot together and the boss should take the side load.

 

However, you lot have filled me with fear!

 

Is there any other way of reconfiguring this arrangement?  Could I just drive the big alternator from the crankshaft with the original drive to the alternator and water pump left undisturbed, and then drive the Jabsco from an additional pulley on the big alternator?  That would reduce the overhang on the crankshaft.  Alternatively drive the Jabsco from an extra pulley on the water pump.

 

If (when🙁?) the crankshaft fails, I can modify the standby engine according to your collective advice.  It would be hard not to have the big alternator as its 130A output is a boon for running the inverter.

Link to comment
Share on other sites

6 minutes ago, GBW said:

Not really.  The three pulleys are locked together by dowels (as explained) and sit snugly on a boss with appropriate diameters.  The bolt pulls the lot together and the boss should take the side load.

 

However, you lot have filled me with fear!

 

Is there any other way of reconfiguring this arrangement?  Could I just drive the big alternator from the crankshaft with the original drive to the alternator and water pump left undisturbed, and then drive the Jabsco from an additional pulley on the big alternator?  That would reduce the overhang on the crankshaft.  Alternatively drive the Jabsco from an extra pulley on the water pump.

 

If (when🙁?) the crankshaft fails, I can modify the standby engine according to your collective advice.  It would be hard not to have the big alternator as its 130A output is a boon for running the inverter.

AHH, this being done for electrical reasons!!

Why do you need such a big alternator?

What electrical loads are you using, there may be a different solution.

 

Bod.

Link to comment
Share on other sites

2 minutes ago, Bod said:

AHH, this being done for electrical reasons!!

Why do you need such a big alternator?

What electrical loads are you using, there may be a different solution.

 

Bod.

I did say!  The inverter.  The various mains powered items on the boat draw 1000-1500 watts.  Turn that into 12 volt watts and you will see the reason.

 

I better solution I agree, would be a separate generator which I have but is petrol and needs to dug out of the deep locker.  If I could find a small diesel generator that could be installed in the stern cabin, that would be great.  I could put up with the noise.

Link to comment
Share on other sites

  • 2 weeks later...
On 23/07/2022 at 12:18, john.k said:

If the crankshaft thread is mangled,then Id suggest you convert to an oversized thread like 3/4x 16 ,or maybe 3/4x18..(depending on whats there.).....as the motor is in pieces ,Id suggest the new thread is done in a lathe,to maintain factory alignment and fit..

I retapped the end of the crankshaft 5/8" UNF as advised.  With around 5 inches space between it and the bulkhead, and using a spanner as a wrench, it was not easy. I used the new boss as a guide and the tap eventually picked up the undamaged thread.  The bolt head was cross drilled and wired to two pins through the washer into the outer pulley.

It ran true.  I didn't replace the belt to the large alternator to ease the load.

 

The repair got us home to Cardiff.

Link to comment
Share on other sites

9 minutes ago, GBW said:

I retapped the end of the crankshaft 5/8" UNF as advised.  With around 5 inches space between it and the bulkhead, and using a spanner as a wrench, it was not easy. I used the new boss as a guide and the tap eventually picked up the undamaged thread.  The bolt head was cross drilled and wired to two pins through the washer into the outer pulley.

It ran true.  I didn't replace the belt to the large alternator to ease the load.

 

The repair got us home to Cardiff.

Well done, perseverance paid off.  👍

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.