Cut Balance Pipes

[David Morris]

Hi all,

One of our local members has had difficulties with his Javelin engine and upon opening up the tappet chest inspection covers was surprised to see that both balance pipes had been cut in the past and 'repaired' with short lengths of rubber pipe, held in place with jubilee clips. One of the rubber pipes had split. He overcame the rough running by replacing the rubber hoses.

My question is why had these pipes been cut? On one side, a logical explanation might be that it was cut to give better access to the crankcase securing bolt, which is a bit buried in the 'trough'. But this does not explain why both sides had been cut?

Another possible explanation might be that the crankcase faces required re-working and the cylinder head ends of the balance pipes were removed and then re-seated. If this was the case, is there a recommended 'stand-proud' dimension for these tube faces upon re-assembly? Engines have locally been reassembled with the faces of these tubes flush with the crankcase face, with no detrimental effect.

Any ideas?

Many thanks,

David

[Forumadmin]

One possibility is that the tube between the crankcases leaked. Rather than fix it, the balance pipe was routed outside the tappet cover.

I have had blocks resurfaced and not worried about the protrusion of the balance tube.

[prsquire]

I've just had my crankcase machined. I'm interested to know how well the engine ran without restoring the protrusion of the internal balance pipe.
It has been suggested that I make flanged inserts (ferrules) with the correct ID from the correct thickness brass shim. A simple stamping job done at home. The finished ferrule would then assembled into the crankcase with a little smear of Loctite 680.
I'd be interested in your thoughts ?

[Keith Clements]

Like a person with a blocked nose!

I am interested to know what you have had machined on the block.
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I was looking at a block yesterday which had a 1/4" copper pipe with a compression fitting in the tappet cover connecting it to the cut off balance pipe from the carb. The copper pipe went through the hole that supposed to have the joining balance pipe in it. But it was hacked off after about six inches so not sure if this was supposed to go into the other half of the block.

Perhaps it threaded through the original balance pipe and was a mod to get over a problem with a leaking seal. More trouble than it was worth I suspect. It was just a passing glance as I had other things I was looking for.

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When putting in the balance pipe please refer to the Tech Notes to make sure you are fitting the correct one. Obviously make sure you take out the old seals and fit new O rings.

[prsquire]

I've had a great deal of work done to the series 1 engine including enlarging the oil feed galleries. The head surfaces have been machined, hence the balance pipe is now level with the crankcase surface. Amongst other things I've replaced the camshaft and crankshaft, obtained new pistons. To explain the amount of work done I've attached the job sheet from the machine shop.
Now I have the job of putting it all back together. which is why I was asking about the balance pipe.

[Keith Clements]

Impressive! Let us hope it is on the road soon and you can enjoy it.

Did you have the block crack tested all over? We have found that a large percentage of old blocks may be porous in some places, so some have had them pressure tested.

[David Morris]

Hi all,

Yes, we have a system of air pressure testing the blocks, using the idea of pressure testing central heating systems with air, before letting water near the systems. John Airey or Nigel Woodford I am sure could supply details. Come to think of it, we should perhaps have a set of the blanking adapters and tools available within the club?

As Keith says, we find a pass rate of only about 15%. It is rare to find a later set of blocks that pass the test without leaking somewhere. I was talking to David Birch recently, one of the last technical apprentices at Jowett's, and he commented that without looking at a set of blocks at Jowett's they could tell instantly whether it was an early set or a late set by the weight of the blocks. The earlier blocks being so much heavier, despite the extra webs and strengthening in the later blocks!

All the best,

David