Jump to content

A tale of two JP3s


Giant

Featured Posts

Right - any good tips on getting that gudgeon pin out, and the remaining valve rocker shafts too? I'll be going back tomorrow or Weds for another bash at it. I sprayed in a load of penetrating oil at the weekend so maybe that'll help.

One of the rocker shafts still has a retaining screw in place which the head has come off, so I'm going to have to drill out and extract that, but I don't know if that's actually what's stopping it. The other one has both screws out but still won't budge. I've taken the tappet screws out and turned the crank such that there's no force on the rockers.

Just to further complicate things both shafts still have right-angle fittings screwed into the forward ends for the greasers, which can't be unscrewed because they hit a raised area on the sides of the heads. I don't want to abuse these and end up trashing the internal threads.

Link to comment
Share on other sites

Well that was a bit of a flop. Is there such a thing as a "screw extractor extractor?" :banghead:

DSC_7113.embedded.jpg.bc0d851ecfae835d0e3599ee29c57185.jpg

Despite not getting that out I did manage to tap that shaft enough to get it moving towards the next cylinder head, but coming back the other way I haven't been able to get it more than a couple of millimetres out of the head. Also tried to use it to push the one in the next head, but that's still thoroughly stuck too.

No further with the gudgeon pin either - I will make up a puller.

Edited by Giant
Link to comment
Share on other sites

I seem to remember the fitter that removed mine used an old jp gudgeon pin as a drift to drive it out, once the circlip had been removed. I wonder if you could use a small drill to drill several holes around the outside of the broken easy out  to have a chance of removing it. Most jp heads i've seen only have a retaining bolt at one end of the shaft, so if that one is damaged its probably not the end of the world.

Link to comment
Share on other sites

Try heating the piston with a hot air gun.  The ally piston will expand more than the steel pin so it becomes easier to get out.  You will probably still need a puller.

Stud/bolt extractors are the work of the devil.  They often make things worse because as they screw in they expand the stud and tighten its fit in the hole.  They are also brittle as you have found. A better solution is a left handed drill of near tapping size, ( which often will bring the broken part out)  then, if needed,  a tapping size drill and finally re-tap to clean the threads up.  

To get the broken stud extractor out you will probably need to drill the whole thing out with a solid carbide drill bit in a drill press  (MSC http://www.mscdirect.co.uk  sell carbide drills but they are not cheap!)  or find someone who can spark erode the extractor and stud out.  Probably not cheap either:(

 

N

Link to comment
Share on other sites

Getting the broken stud out - a couple of ways. Find a engineering place with a spark eroder and take the head to them.

                                                             Or

A blunted left hand centre drill might do the trick. I saw it for the first time and could not work it out at first. Milling machine going the wrong way for drilling and a centre drill in the chuck  But I kid you not they do exist.

http://www.phantomdrills.co.uk/shop/product/left_hand_drill_bits

Link to comment
Share on other sites

Once we've got that head off I will put it in the big drill press and drill out the remains. If I can do a neat job then all the better, but as BWM notes, only one retaining bolt is really needed, so if I mess up the thread it's not the end of the world - and could always tap to the next size up.

The need to remove the rocker shafts to get the heads off really does seem like a bit of a design flaw on the JP. It's easy to get the shafts out once the heads are off! I actually wonder if it would be possible to create a tool that could get the hollow stud nuts off without removing the rockers.

Anyway, we have plenty to do for now in cleaning up the bits we've already taken off and brought home.

Edited by Giant
Link to comment
Share on other sites

16 hours ago, Giant said:

Once we've got that head off I will put it in the big drill press and drill out the remains. If I can do a neat job then all the better, but as BWM notes, only one retaining bolt is really needed, so if I mess up the thread it's not the end of the world - and could always tap to the next size up.

The need to remove the rocker shafts to get the heads off really does seem like a bit of a design flaw on the JP. It's easy to get the shafts out once the heads are off! I actually wonder if it would be possible to create a tool that could get the hollow stud nuts off without removing the rockers.

Anyway, we have plenty to do for now in cleaning up the bits we've already taken off and brought home.

It certainly is a design flaw! The individual heads should make it a breeze to repair a fault on one cylinder, but unless the fault happens to be on no 1 you've had it. 

It would be nice to obtain a tool to remove those nuts on the hollow studs, but being able to torque them up would scupper that, I suspect.

Link to comment
Share on other sites

On 4/25/2017 at 01:41, Giant said:

Right - any good tips on getting that gudgeon pin out, and the remaining valve rocker shafts too? I'll be going back tomorrow or Weds for another bash at it. I sprayed in a load of penetrating oil at the weekend so maybe that'll help.

One of the rocker shafts still has a retaining screw in place which the head has come off, so I'm going to have to drill out and extract that, but I don't know if that's actually what's stopping it. The other one has both screws out but still won't budge. I've taken the tappet screws out and turned the crank such that there's no force on the rockers.

Just to further complicate things both shafts still have right-angle fittings screwed into the forward ends for the greasers, which can't be unscrewed because they hit a raised area on the sides of the heads. I don't want to abuse these and end up trashing the internal threads.

To remove my gudgeon pins I poured boiling water from the kettle onto the piston crown. Do it a little at a time and it should do the trick.

Link to comment
Share on other sites

  • 6 months later...

Right. This project was on hold over the spring and summer while we focused on paint and varnish but now that winter has set in we are picking it up again. We have also moved engine #2 closer to home so it is now much easier to go and work on.

We never did succeed in getting the other two valve rocker shafts out, but we were given a great tip by Steve Waddington over the summer when we stopped by at the yard at Swinton - how to take a JP head off without needing to extract the rocker shaft!:

  1. Pick one of the valves.
  2. Turn over to a position where the cam for that valve is not pushing on the follower, and the piston is well clear of the valve.
  3. Lean really hard on the top of the valve side of the rocker to fully compress the valve spring, thus lifting the other end of the rocker up.
  4. Keep leaning while you:
    1. Extract the pushrod, which will now just fit past the rocker.
    2. Sneak your 3/4" Whitworth socket (which will also just fit past the rocker, if it's the right sort) onto the nut on the tubular stud.
    3. Attach a socket drive extender, which will end up sort of jammed up against the rocker.
  5. Gently release the valve spring.
  6. Now you can unscrew the nut with the rocker and shaft still in place!

Simple in retrospect but would never have occured to me, and I'd never heard of this trick.

So thanks to this, and a gudgeon puller I made up, I have now got the other two heads off and their pistons and con rods out.

I have measured the remaining two crank journals and they match the first one we looked at: pretty much exactly 20 thou under 3". So that seems to support the previous theory that this crankshaft was already ground to 0.020" undersize and has seen very little wear since.

The surfaces of the big end bearing shells look okay but there are some dings and chips around the edges of a couple, and around the oil hole in one of them, so I'm guessing those will want replacing.

Now pondering what to take apart next, and worried about any pitfalls in doing so. About the only easy looking thing left to come off is the water pump. Then I suppose getting the gearbox off, which I'd like some tips on, as that's heavy and seems like it must need careful support as it comes off the end of the shaft.

After that we must be into territory where we need to borrow a hydraulic puller, for the flywheel and cylinder liners?

Tips and pointers welcome - we've not been this deep in one before. :)

Link to comment
Share on other sites

  • 2 years later...

Well, I suppose we should start updating this thread again.

 

The bottom end & gearbox of engine #2 have been with @RLWP and @Mrs Tawny Owl for a while now getting a complete strip down & rebuild. The crank has been reground, reinstalled on new main bearings and everything is looking very shiny.

 

Sometime soon, we will be taking the boat into to drydock, and while we're there we'll have engine #1 craned out through the deck, and the newly rebuilt bottom end of engine #2 installed in its place, after taking the opportunity to strip the area under it back to bare metal and repaint. Then we'll be rebuilding the top end onto that, with a mix of parts from engines #1 and #2.

 

There's a complicating factor with the reduction boxes, because the one from engine #2 was water damaged and unusable, and it's not possible to remove & strip down the installed one until we have the engine out. So we're going to need to get that apart, deal with any issues and get some paint on it before reinstalling. We're hoping there's not too much wrong there - it runs smoothly, and looks to be in reasonable condition on the inside as seen by an endoscope down the dipstick hole.

 

Meanwhile, we've been getting engine #1 as ready as we can for its final voyage, swapping in some top end parts from #2 that are in better shape, and installing some new bits, all of which will then get transferred to the newly rebuilt bottom end.

Link to comment
Share on other sites

Today's mystery, however, is in the exhaust manifold that came off engine #2. We'd like to use this one, because the troublesome joint to the silencer is in much better shape. But while having a look through the channels in it yesterday, I found this inside the exhaust - a bent rod around 3-4mm in diameter. I could just about reach each end of it with a finger, through the forward two exhaust ports:

rod1.jpg.bf9cf8cb211143d260f4c52e7422c4c8.jpgrod2.jpg.dc937cf7493ef154df17b2b55bda1149.jpg

At first I thought it was just lodged in by being bent around the corner, and tried to free it, but eventually I realised that both ends were free, and that all I was doing was bending it around a point in the middle where it was welded to the casting - here, you can see where the weld is and where I've dislodged the carbon either side by bending it:

rod3.jpg.6846f4c1c3a877d83f6986c893b94771.jpg

So it seems like this is a brass brazing/welding rod that's been used to fix a hole at that spot, and then left in there. For context, it's positioned like this (in green) within the manifold, with the weld (circled) seeming like it's on the edge of that round feature on the side of the casting.

exhaust1.jpg.3c515ffc17001893b7dca9c0344dc52c.jpg

It seems like that round feature is at the end of a boss, that shows up as a ridge across the exhaust channel. But it doesn't seem to be a tube that connects to the water side of the manifold, and it would make no sense to have a tube across there - the water flows along the manifold below and to the side of the exhaust channel.

 

So why was it necessary to weld up at this point? Any ideas what's gone on here?

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.