Author Topic: The mongrel  (Read 787 times)

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Offline tck

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The mongrel
« on: 23 Aug 2020 at 11:04 »
Will this ostensibly MK4 motor ever stop giving me puzzles?
As I have said before it had a rev counter drive, and plus heads. one side had plus push rods and one side standard  on looking at the cams they are marked with a T but that's not to say they are original profile I certainly could not tell. Now I have taken off one inlet valve and I find (see below) there are 3 springs so I guess they are plus valve springs  are they still available ? can I use standard springs ? are the caps collets different? at least the valves and guides look in good condition but will standard valves fit? what are the standard valve head sizes? so many questions (NB the engine also sported larger 276 carbs on manifolds I thought the racing trim without lights was a bit of a posers dream but now I am not so sure)


Offline eddie

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Re: The mongrel
« Reply #1 on: 23 Aug 2020 at 11:34 »
The valve and springs in the photo are definately 'Plus'. If you are looking to replace the valves, be careful - there were a couple of options with valves (different collet arrangements). If you decide to stick with the 3 spring set up, I can supply a new set of springs.
  The cam profile on 'T' and 'S' cams is the same - the 'S' cam has more lift and slightly longer opening by virtue of a smaller base circle. I believe the 'Plus' No3 cam goes a step further, but also has the lobes timed a little closer (by about 4 degrees). Evidently, the original cams and the No2 cams had much fiercer opening, and gave the rest of the valve gear a very hard time!

  Regards,
                  Eddie.

Offline tck

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Re: The mongrel
« Reply #2 on: 23 Aug 2020 at 12:01 »
Thanks Eddie
Have you any indication of the  free length for the plus springs? Thankfully the valve stem I have looked at is very good condition. I have tried two valve spring compressors on the heads and both are wilting under the strain of compressing the springs (or freeing the collets ?) in the end under maximum pressure a sharp tap with a copper drift on the valve cap dislodged one collet and the valve edged by the other on release Certainly the linkage tool shown in the handbook would never have compressed it. NB: there was a thin washer on the base of the spring I have omitted from the photo.

Offline eddie

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Re: The mongrel
« Reply #3 on: 24 Aug 2020 at 17:26 »
I have checked the length of the new springs  - all 3 springs are 1.750" long. The inner and outer springs are wound right handed, and the middle spring is wound left handed.
  The washer you mention is probably one of the shims that were available to adjust the fitted length of the springs - this became more important as the 'Plus' engines were pushed harder and harder.

  Regards,
                 Eddie.

Offline tck

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Re: The mongrel
« Reply #4 on: 25 Aug 2020 at 14:48 »
Can anyone point me at a stronger valve spring compressor ? I have only managed to free one of my valves I have broken one cast compressor and the current one I have had to weld up to stop movement and its actually bending the arms edge on! measuring the cap it has not moved a jot I even turned up a cup and had it in my big vice and it would not move ( heat has been applied) all the usual pansy ones I use on Vincents and Triumphs would bend in a second!
What did Freddie Dixon use I wonder

Offline eddie

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Re: The mongrel
« Reply #5 on: 25 Aug 2020 at 14:56 »
This is a bit fiddly, but find a couple of steel bushes about 3/4" bore - place one against the valve head and the other against the spring cap. Then squeeze the whole lot in the vice - once you have shifted the cap, the standard spring compressor will work!

Eddie.

Offline tck

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Re: The mongrel
« Reply #6 on: 27 Aug 2020 at 13:36 »
Well  I have tried that very good idea in my biggest vice with a 3/4" copper bar against the valve head and a short steel tube against the cap I wound it up with a 3ft scaffold bar till I was worried the vice would give way but there was no movement I also jarred the cap at full pressure with a copper drift  with no result. I can inspect the cap and it is not near the collets or valve end so I shall have to find someone with a hydralic press, something has to give!


Offline tck

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Re: The mongrel
« Reply #7 on: 27 Aug 2020 at 13:37 »
here is a close up every thing is clear

Offline Neville Heath

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Re: The mongrel
« Reply #8 on: 27 Aug 2020 at 16:12 »
tck  I too have found Plus valves hard to get out but do not remember such an extreme problem as you.  Attached is a photo of the Sykes Pickavent tool that I use. Note the modified strengthened cup welded on. Also that it is bent from hard use. 
You would do better to remove the rocker block so you can get at it better.  Also forget the vice as you cannot hit it. A good hit whilst under load  has always worked in the end for me. Good Luck!
Neville 



Attachments converted to linked images - Dave, 07Feb2021
« Last Edit: 07 Feb 2021 at 07:08 by Dave »

Offline tck

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Re: The mongrel
« Reply #9 on: 29 Aug 2020 at 18:26 »
Done it!
But it took an 8 ton bottle jack two lengths of all-thread a bent spanner and a good wack of a copper mallet. only 2 more valves to do! :roll:

Offline tck

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Re: The mongrel
« Reply #10 on: 01 Sep 2020 at 11:00 »
Eddie I sent you a PM about 90+ valve springs

 

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