The anatomy of a National

[Chris Pink]

My National is apart, i have diagnosed, so far, a leaky valve cage joint - machining booked, new piston rings - obtainable, and this;

 

Damage to the top lip of the liner.

 

Given that i don't particularly want to remove the block and replace the liners, what can i do with the engine in situ?

 

The copper head gasket was damaged at this point (probably when the head went down) and it has been blowing for many years causing the corrosion in the photo. There is corresponding damage on the head but not so bad.

 

Can i build this up with JB Weld - will it stand the heat and pressure?

 

 

Other questions;

 

Does there exist a workshop manual, i have a maintenance manual and a parts list but no book with tolerances and settings?

 

What are the spot marks on the liners? Are they wear indicators?

 

Is there any difference between JB weld and Chemical Metal? (I have the latter in stock).

 

What does the bung in the top of the piston do? One is looser than the other, does it matter?

 

There is no mention in the parts list of a paper gasket over the major part of the head/block joint, there was a lot of sealant in here and the remains of something that may have been a paper gasket, should there be a gasket here? Would i do any harm by putting on in anyway to seal over some of the imperfection in this surface.

[wonderdust]

I personally think JB is better than chemical metal, i do not know if it would stand the pressure but according to the web site it is ok for temps up to 260 degrees C. I wonder if there is anyone out there with a National that could use a digital thermometer to get an idea of the head temp.

[Chris Pink]

I personally think JB is better than chemical metal, i do not know if it would stand the pressure but according to the web site it is ok for temps up to 260 degrees C. I wonder if there is anyone out there with a National that could use a digital thermometer to get an idea of the head temp.

 

It is used to repair block cracks in fairly modern engines and the fact that the engine has run for around 8-10 years with this fault makes me want to give it a go.

 

My tube of chemical metal does look a bit aged so I will probably splash out and get some new JB weld.

 

I do not want to remove the block, or fit new liners, oh no.

[mikevye]

Hi Chris, sorry to be negative but it looks like you've got a real problem there. RN have a web site with an enquiry page which I would be inclined to send the photos to and ask their opinion. The problem with welding in situ is that machining is still required and with proud liners this is not possible. We used a product named Belzona in the RN to good affect it was everywhere! With all surfaces cleaned to as new possibly with acid this product might work in the areas shown apply it as neatly as possible to keep filing to a minimum. I'm only guessing as to the spot marks on the cylinders some form of lubrication retention? and the the domes crankcase pressure relief?

[Timleech]

Hi Chris, sorry to be negative but it looks like you've got a real problem there. RN have a web site with an enquiry page which I would be inclined to send the photos to and ask their opinion. The problem with welding in situ is that machining is still required and with proud liners this is not possible. We used a product named Belzona in the RN to good affect it was everywhere! With all surfaces cleaned to as new possibly with acid this product might work in the areas shown apply it as neatly as possible to keep filing to a minimum. I'm only guessing as to the spot marks on the cylinders some form of lubrication retention? and the the domes crankcase pressure relief?

 

Their opinion is quite likely to be 'you need to spend lots of money with us to sort it out' :lol:

Belzona is pretty good stuff, I would certainly give it a try. It might not last 100 years but done carefully it might well see you through until more work is needed as it's not in direct contact with hot combustion products. It needs cleaning to bare metal with a bit of roughness to key properly. It looks as though you've got a fair bit of cleaning to do anyway!

 

If the plugs in the piston tops are at all loose, that needs sorting. I'll try to post a pic later of what happens when they're left loose for too long

The plug goes up into the 'clerestory' combustion chamber between the valves, part of the basic design.

To the best of my knowledge the dots in the liner wall indicate a chromed liner, they are etched areas to hold a little oil.

 

Tim

[mikevye]

Their opinion is quite likely to be 'you need to spend lots of money with us to sort it out' :lol:

Tim

 

You're probably right Tim, but ever the optimist there's no harm in asking and it would be interesting to find out the telephone numbers straight from the horses mouth keep us informed Chris

[Proper Job]

You can take the liner out in situ without to much trouble. The heads already off, so drop the big end and lift the piston out.

 

Don't forget to slacken off the ring at the base of the liner (inside the block), like what I did. I went in to some detail on my blogg regarding my fight with the liners:

Liner battle

Doh

 

I would look at getting it out, getting the corroded bit welded/braised up then doing a simple re-machining of the repaired area to true it all up.

 

I don't think that plastic metal/belzona would stand the temperature of pressure.

[Chris Pink]

You're probably right Tim, but ever the optimist there's no harm in asking and it would be interesting to find out the telephone numbers straight from the horses mouth keep us informed Chris

 

 

Well.

 

 

I have spoken to the horse (sorry, Allister - why do they all spell funny at Russell Newbery?) and i need to sit down.

 

the advice;

 

don't do the piston rings yet. bad practice to put new rings in old pistons, not round no more, get the valve problems sorted out first then examine compression (450-500psi, running on one cylinder check the other.), blow by through the oil filler and some breather i've not even found yet. Drop the piston and check the gap - should be .012" if around 1/16" fix, check the ring grooves for wear, might need new piston.

 

Telephone numbers; new piston £300 each plus machining to fit National, liners £200 each plus machining or Tony Redshaw fit an insert ditto.

 

Not at all sure about pulling the liners, Mr Job, will probably try the bodge repair first. It's all very well pulling the liner out when the block is on the bench but the amount of crap likely to drop into the sump is a bit scarey. I am not an engineer, more semi-skilled fitter.

 

Bung needs fixing so pistons out anyway.

 

The other numbers i garnered were;

 

.070" gap between piston and head determines size and number of copper head gaskets (they come in .008", .018", .032" (standard), .048", the .008" is used in conjunction with the others. The head stud torque is around 80 lb ft, the lead wire test should be done at around 50 lb ft

 

the Swallow link is a good one, thanks Steve.

Edited October 6, 2009 by Chris Pink

[Chertsey]

Feel free to talk to us too if it's any help - well, PaddingtonBear is the horse's mouth in our case. We have some National pistons, liners, con rods etc from when RN replaced them with RN ones, if it might be if any help. PM PB

[Proper Job]

Feel free to talk to us too if it's any help - well, PaddingtonBear is the horse's mouth in our case. We have some National pistons, liners, con rods etc from when RN replaced them with RN ones, if it might be if any help. PM PB

I've got all of the dimension data (wear) for Warriors pistons and liners if its of any help.

 

Your liners look pretty good from the photo, just the corrosion problem at the top?

[Chris Pink]

Your liners look pretty good from the photo, just the corrosion problem at the top?

 

Yes, that's right. Allister said 'as long as there's no flakey chrome don't be hasty about replacing them or the rings'

 

Been reading your blog, nice restoration - though far beyond the current brief! Did you sell your engine in the end?

 

An internal micrometer? Not sure I'm ready to take the step from hammer to micrometer as weapon of choice

[Tam & Di]

Other questions;

 

What does the bung in the top of the piston do? One is looser than the other, does it matter?

 

I can certainly tell you what the hardened steel "bung" does at the next stage of evolution.

 

The exGUCCC wideboat Progress had a National when we rescued it from the Cowley dredging tip many years ago. We were en route to the Thames to sit it on the foreshore to do some hull work when one of these bungs came adrift. It made a very nasty mess of the piston and the head. Luckily we were not far from the BWB Bull's Bridge repair yard and they were able to supply all new parts ex-stock. Ahh, the good old days! I don't think the Tesco store which now sits there stocks them though.

[Chris Pink]

I can certainly tell you what the hardened steel "bung" does at the next stage of evolution.

 

The exGUCCC wideboat Progress had a National when we rescued it from the Cowley dredging tip many years ago. We were en route to the Thames to sit it on the foreshore to do some hull work when one of these bungs came adrift. It made a very nasty mess of the piston and the head. Luckily we were not far from the BWB Bull's Bridge repair yard and they were able to supply all new parts ex-stock. Ahh, the good old days! I don't think the Tesco store which now sits there stocks them though.

 

How are they fixed? the parts drawing shows it with ridged sides, a push fit.

 

Having failed to order a pressure washer from Tescos because they refuse to admit my postcode exists, i don't think I'll bother them about National parts.

[Tam & Di]

How are they fixed? the parts drawing shows it with ridged sides, a push fit.

 

Having failed to order a pressure washer from Tescos because they refuse to admit my postcode exists, i don't think I'll bother them about National parts.

 

Sorry Chris, can't help with that detail. The new head I got came with the plug attached (firmly!)

[Steve Priest]

I'm not sure I've much to add. There is a manual and parts list which sound like the ones that you have, There is nothing that gives more detailed information that I know of. The parts list is useful, as it has good cross sectional drawings.

 

National head gaskets were a copper ring on the top of the liner, the waterways were sealed with rubber o rings and brass ferrules, and the push rod tubes with cork washers. There was no paper gasket used, perhaps if you have found remnants of one it was somebody's previous attempt to stop it leaking. Russell Newbury used a fibre gasket for a while, but have now gone back to o rings. I do have some of these fibre gaskets, (I'm not sure wether R. N. keep any), they may be worth a try. The Russell Newbury copper head gaskets in different thicknesses are a Godsend, the bump clearance was adjusted by fitting shims between the con rod and the top of the big end bearing, which is seperate.

 

As Tim said, Nationals had perforated chrome liners, the dots visible inside hold oil.

 

Best of luck with it,

 

Steve

[Chris Pink]

The saga continues;

 

....and i consider myself to be a very very lucky person indeed, a small extra piece of metal fallen off and....

 

Anyway, I have a list of faults to cure now, hopefully the end of it. Maybe a little shortsighted but i am not going to dismantle the main bearings.

 

going to be interesting finding all those little bits of metal in the sump... the sump I can't even get to.

 

 

Opinions on the replacing the other big end as a matter of course? if it ain't broke, don't fix it? or do it anyway as I have the engine in bits?

 

I won't know until tomorrow how obtainable the shells are.

[Barry]

The other needs to be at least checked looking at the state of the one in the photo - the white metal is very thin where it has broken away so it is likely that the other big end bearing will be in a similar very worn condition and ready to go if it hasn't done so already

 

I'd check the other and be prepared to replace it as well

[WotEver]

Looking at that shell, what's the state of the crank journal? There's a fair bit of scuffing and I'd have thought if the crank looks the same then you'll wreck new shells in double-quick time.

 

Personally, no matter how much of a pain I'd definitely drop the other big end and if it's in similar condition then the mains are going to have to be checked.

 

I feel your pain.

 

Tony

[tomsk]

The saga continues;

 

....and i consider myself to be a very very lucky person indeed, a small extra piece of metal fallen off and....

 

Anyway, I have a list of faults to cure now, hopefully the end of it. Maybe a little shortsighted but i am not going to dismantle the main bearings.

 

going to be interesting finding all those little bits of metal in the sump... the sump I can't even get to.

 

 

Opinions on the replacing the other big end as a matter of course? if it ain't broke, don't fix it? or do it anyway as I have the engine in bits?

 

I won't know until tomorrow how obtainable the shells are.

 

 

What a mess!! I think you at least need to inspect the other one!!

[Chris Pink]

What a mess!! I think you at least need to inspect the other one!!

 

Iindeed, one of the good things about such robust technology is that the other big-end came out leaving the piston behind.

 

it 'looks' fine but i am sending it off to be checked.

 

The offending journal is smooth with no scoring but has a slight ridge where the oil groove is, and there is a corresponding groove in the matching shell.

 

Choices are;

 

regrind crank, find undersize bearing shells

polish existing journal and fit new shells

stick my head under the duvet

 

I am trying to avoid 1 and 3. The engine will be moved within the next 6 months into my new boats so maybe at that time checking the crankshaft and main bearings would be a good move.

 

Piston rings and liners 'look' good but I checked the gap yet.

[Timleech]

Iindeed, one of the good things about such robust technology is that the other big-end came out leaving the piston behind.

 

it 'looks' fine but i am sending it off to be checked.

 

The offending journal is smooth with no scoring but has a slight ridge where the oil groove is, and there is a corresponding groove in the matching shell.

 

Choices are;

 

regrind crank, find undersize bearing shells

polish existing journal and fit new shells

stick my head under the duvet

 

I am trying to avoid 1 and 3. The engine will be moved within the next 6 months into my new boats so maybe at that time checking the crankshaft and main bearings would be a good move.

 

Piston rings and liners 'look' good but I checked the gap yet.

 

You won't find any 'shells', the white metal is cast directly into the bearing halves then bored to size so it really doesn't matter too much what the size is (from the cost point of view).

Two things worth doing (the first you'll need to do anyway at some stage):-

get a micrometer the right size and check the journal diameter at three points (middle and either side), first 'top to bottom' (max wear position), then repeat 'side to side' (minimum wear). You want to be looking for a maximum difference of no more than about 2 thousands of an inch, much more than that & you will need a regrind. 1 thou or less is much better, your new bearings will last longer.

Second thing, set up a 'dial gauge' or 'dial indicator' to measure vertical movement of the crankshaft at the flywheel end relative to the crankcase, not the engine mounts. Then use a jack or hoist to lift the flywheel and measure the movement, this will give you a very rough indication of the state of the main bearings. Again, if it's significantly more than a couple of thou you need to investigate.

 

That big end looks as though it's been 'hammering', either through being run with too much play or possibly too much Easy start etc for starting.

 

You should be able to clean out the sump by removing the cylindrical strainer which bolts in through the back.

 

Tim

Edited October 11, 2009 by Timleech

[soldthehouse]

Iindeed, one of the good things about such robust technology is that the other big-end came out leaving the piston behind.

 

it 'looks' fine but i am sending it off to be checked.

 

The offending journal is smooth with no scoring but has a slight ridge where the oil groove is, and there is a corresponding groove in the matching shell.

 

Choices are;

 

regrind crank, find undersize bearing shells

polish existing journal and fit new shells

stick my head under the duvet

 

I am trying to avoid 1 and 3. The engine will be moved within the next 6 months into my new boats so maybe at that time checking the crankshaft and main bearings would be a good move.

 

Piston rings and liners 'look' good but I checked the gap yet.

Hello Chris if your going to replace this engine in the next six months could you not do it now and then fully overhall this engine once and for all ,as it will save doing quite a lot of the work twice, just a thought based on limited knowledge of the circumstances, regards Stuart

[Chris Pink]

...possibly too much Easy start etc for starting.

 

I'll thank you not to cast such nasturtiums

Edited October 11, 2009 by Chris Pink

[Chris Pink]

Hello Chris if your going to replace this engine in the next six months could you not do it now and then fully overhall this engine once and for all ,as it will save doing quite a lot of the work twice, just a thought based on limited knowledge of the circumstances, regards Stuart

 

 

When you say 'fully' what exactly would you suggest I replace that I'm not replacing or measuring now.

[PaddingtonBear]

(takes deep breath)..................................

 

or better still contact PJ as he has done some of it, I on the other hand paid someone to do most of it. The fact is your engine appears to be totally f**ked and needs to be completely dismantled, cleaned and checked especially if you are going to use it in another boat . The heads need total overhaul, and you know about the bottom end - the crank and bearings have to be machined 'together' even allowing that the crank is usable (I got our crank crack tested and x-rayed) all praise here for Steve Priest who was extremely helpful by pointing me in the direction of crank grinders etc. What a star! and all because he cares about doings things properly.. The biggest problem that we had was the middle bit - conrods, liners and pistons - if your has cast pistons, which is very likely, we were told that it is best to change them for RN alloy ones (again ) and it you do this you need different conrods and liners (RN) and the liners need modifying as do the seals, and you have still got to attend to the ring gear etc. ..................... keep smiling, at least you only have two cylinders, I had three of the buggers.