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Ok so over the last few months I've been stripping down towys engine I needed to do some head work and this is nearly at an end. I last year made it so I could start and stop each indervidual cylinder as well as start and stop in a way that 1 leaver starts and stops both but can also start and stop indervidual  cylinders from another, this was all done on the exhaust side.

 

Both cylinder heads have had complete rebuilds, I'm still in the process of removing the last of the limescale in 1 head unless I find a replacement (I was ment to have one on way but this turned out to be a bigger headache in end turned out to no head and loss of alot of money) 

 

Anyways both heads have had

1. All cleaned and repainted all mating surfaces cleaned and skimmed

2. Intake valve holder has had valves relaped and new seals and guides.

3. Exhaust valves relaped and rebuilt using new guides.

4. The rockers have had new floating oil system and new internal bearing with new holding shafts and end shaft guides.

5. The new decompression system has been revised so I now how leavers both sides of the heads so i can start by hand without having to lean over the engine and can now control each cylinder from either side of the engine and still retain indervidual cylinder running if needed.

6. Had injector guides revised so now has a seal top and bottom meaning there is no chance of water getting out past the guide and to the injectors there are also seals between the injector and guide so no water can get past the top of the injector down to the seat.

 

I'm now onto the next job, piston and liners turns out 1 liner and piston is shot, 1 piston is saveable but the liner is very oversized in the middle, the good piston also has extreme build up of carbon in the very small top grove (see pics) so next job is now new liners and pistons.

20191103_155412.jpg

20191103_155506.jpg

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Nasty seizure on one piston,incipient seizure on the other.......possibly due to your problem with heavy deposit buildup......You should note the black marks on the seized piston are actually a hard alloy of iron and aluminium,and will score a cast iron liner.

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On 05/11/2019 at 00:56, john.k said:

Nasty seizure on one piston,incipient seizure on the other.......possibly due to your problem with heavy deposit buildup......You should note the black marks on the seized piston are actually a hard alloy of iron and aluminium,and will score a cast iron liner.

Yer the liner is shot, the other is overbored and was funny as the overbored one was the low compression the scored on actually had high compression

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Ive had bigger RN s over the years ,mostly E4s and E6s and the D 4s,which were very common here once ,as the DCA bought several hundred gensets with them.They sold them with very low hours,some never started,and still in crates.......then they scrapped all the spares,instead of putting them up for tender.........asbestos scare ,I think....Funny how one day the govt can be taking delivery of a shipload of asbestos lagging,next day there is a panic ,and they are paying millions to get rid of it all.

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  • 2 weeks later...
5 minutes ago, billybobbooth said:

Well 1 head is all but back together, now onto finishing off the 2nd head, then got to sort out some liners and pistons

 

Are these the ones you were thinking of having welding repairs to?  Be interesting to see some photos.

 

 

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No I've got 1 that I looked at welding but it's not possible to guarantee it sealing as it's around the piston dome cutout.

 

The other I'm still working on the limescale but it's almost done.

 

The head has had a full rebuild except for the rockers these are the same but they have had new bushes, everything elts has been stripped and replaced or reconditioned even the valves got reground and guides changed,

 

The water jacket around the injector has been removed all seats cleaned and has been recur and sealed

 

They are having a total rebuild.

 

I'm now stuck on liners and will prob have to reuse 1 piston but the other I've got to find a replacement so will be after 2 liners and an ally piston, will fit new rings.

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My old engine engineer/machinist never fitted the skirt rings to pistons. Reckoned they did nothing but cause seizing due to excessive oil scraping. Long passed now.

On the engines I built that had skirt rings I left them off and never had any oil consumption or seizing problems.

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4 hours ago, Boater Sam said:

My old engine engineer/machinist never fitted the skirt rings to pistons. Reckoned they did nothing but cause seizing due to excessive oil scraping. Long passed now.

On the engines I built that had skirt rings I left them off and never had any oil consumption or seizing problems.

I'm considering putting some piston oilers in. They would be fairly simple to fit as can use the oil return from the original oil filter and mount the boilers to the block cover

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  • 2 weeks later...

Ok, so some progress or not depending how you look at it!

 

So far I need to say a huge thanks to those that have helped me out, there is now a semi plan in place for sourcing new parts, I now have access to new small end bushes including the rod inserts as well as new gudgeon pins and possibly liners too, at the same time I also now have the ability to replace every internal part for the cylinder heads.

 

Now onto pistons I now have 2 usable pistons (again huge thanks my engine would never get back together without it!)

 

Anyways from my engine building background I'm a little confused, I need to find out what the top gap in the piston is for, its 1 of 2 options

1. An expansion gap

2. A thin compression ring grove.

 

Reason I ask is I've not seen another piston with a big expansion grove like this, I've had several talks with people and unable to come to a solid conclusion. I need to find out before I put my engine back together, as I need to avoid the damage that's been done this time, this has been caused from 1 of 2 or 2 of 2 things. 1 is the fact it has ally pistons in with steel piston splash guards still fitted. 2 the car in had got into this very top grove turned to rock hard carbon and scored all my liners and then pistons. (For this reason is this why the engine manual says to strip it down for cleaning every 2500 running hours)

 

The rn engine group used to show a list of there replacement parts with part numbers but now this is gone I'm unable to refer to it for the piston grooves.

 

Any ideas help or pics on the pistons design would be good.

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I would be shocked to find it is another piston ring groove, there are already 3 compression rings, at least 1 of which will be a scraper, an oil ring and the skirt ring. That is quite enough rings to drag down a bore.

Could I suggest asking Hepolite Glacier, they will know?

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1 minute ago, Boater Sam said:

I would be shocked to find it is another piston ring groove, there are already 3 compression rings, at least 1 of which will be a scraper, an oil ring and the skirt ring. That is quite enough rings to drag down a bore.

Could I suggest asking Hepolite Glacier, they will know?

Hence my confusion as all it did on mine was fill with carbon and then cause problems, the grove is also cut to the exact same depth as the piston groves and is also of the right thickness for a thin first ring, alot of even old pistons have a thin compression ring the a thick second the a scraper then a oil ring

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I have a dismantled National DM2reputably of 1936 vintage. This engine has chromed bores with hundreds of dimples in the surface, I have no idea if this was OEM manufacture, possibly not as there is evidence of a major rebuild at some time in its life. The pistons when removed were is an excellent state with no galling of the skirts. The pistons were fitted with a full set of rings and the crankcase splash guards were in place.


Regarding the thin top groove, my thinking is that there are two possible reasons for its 
existence. Firstly as a heat barrier and secondly to limit heat induced distortion or both. Interestingly neither groove shows any build-up of carbon.


I also have an original copy of the Russell 
Newbery Spare Parts List for 'D' Type multi-cylinder engines", publishment date unknown but the address listed on the cover is "Essex Works, Dagenham, Essex" which might help date it. The sectional drawing in the back shows a DM3 engine but most parts are of course interchangeable. The drawing shows that the RN pistons also had the thin top groove.
 
If you are REALLY desperate I will try to find a way to scan/photograph you a copy of the RN parts list but I am more abacus than Win10 and I HATE laptops . . .

 

 

 

 

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No that's fine, the info you have given is helpful, yes I've seen a liner before that was a dotted liner, I've got national ones and these arnt but yours could just be another maker of the liner as I know of at least 3 diffrent pistons used 2 ally by diffrent makers.

my only next bit to find are replacement piston rings  I've got all except the 2 oil rings but I'm going to sort a sorce for both rings, this way I have a way of getting easy spares and can also update others who are building up a list like me of were parts can be made or got from.

 

I already have a sorce for all the gearbox parts. Except the casings.

I prob know someone who can make rods too be it they would prob be forged rods than cast.

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  • 2 months later...

Ok so I'm 5 months into my national (unwanted) rebuild.

 

I've currently got 2 fully refurbished and modded cylinder heads, new rings, liners (on way), rebuild conrods, cleaned and checked pistons, rebuilt oil pump, rebuild and re located oil filters and cooler, replaced and redone all oil lines, redone all water pipes and lines including filters, all removable plates intakes ect have been removed and cleaned.

 

Now onto painting.

 

Need some ideas for what colours?

 

My flywheel is done in a blue front and back with what will be black starter parts, and the outer I'd done in a fire engine wheel style, (its diffrent but looks really nice)

 

The current engine was all green bit light and was thinking of going brg main engine with all water pipes red, all oil lines black rubber and copper metal (just polished so can see leaks) and the writing on the engine then in red.

 

But I'm also considering blue for the block and gearbox

 

Any ideas please

 

I dont mind green or oxford blue but at same time kinda want something a little diffrent and not yellow

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  • 2 weeks later...

Right random bit of help needed the intake covers (big 5.25" round discs) on the side of each head, mine are cast and are around 11mm thick with a step in of 3mm making the middle of the plate 8mm

 

Now I get there so thick given there cast, but given they are only a cover plate could I get away with 4 or 6mm brass? If I have to go thicker I can but there is a big ££ difference for 8-12 compared with 3-6mm given there 5.25" diameter. I was hoping to use 6mm. (I did look at cast bronze but you cant get them easily in 5.25" or 5.5")

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  • 4 months later...

OK just an update.

All heads fully rebuild, new valve guides, new intake valve chest seal, new rocker bushes, new rocker bars, new brass water seal around the injector with seals, rebuild injectors with new nossles, re designed droppers on the rocker covers, new decompression lifters and levers aswell as 2 sided and individual cylinder shut off. New gaskets and head caps for water and intake and exhaust covers. Recut injector seats. All heads fully delimescales and all water ports checked and made sure all flow water freely including round exhaust outlet. Head .002" skim.

 

New liners (copies of genuine national 1940s liners), new liner seals, cleaned and prepped block for liners to go back in, (just need to sort the very small crack at the week point at the back of the block.) Top of block 0.002" skim.

 

Fully cleaned and piston ring groves  checked pistons, new gudgeon pins and retaining clips, New con rod small end bearing honed to new gudgeon pins, new rings all gap checked to new liners. New rod shims.

 

Checked and measured big end bearings, cleaned and checked big ends on crank.

 

I can now supply any of the above parts that I have replaced. Liners can be ground to fit r/n

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7 minutes ago, NB Esk said:

 

Sounds good, any chance of some photos?  Also, what are the "new rod shims"?  Thrust shims?

 

 

I've got a few pics ill post but didn't do many as gone along due to when I've been doing the work and having to just get it done,

 

Rod shims sit between the conrod and bearing housing. There use to be 2 ways to adjust the hight of the piston,

Under the rod

On the cylinder head gasket, there use to only be 2 head gaskets the rest was done from the rod, now new rn have fixed rod and adjust from the head only.

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1 hour ago, billybobbooth said:

I've got a few pics ill post but didn't do many as gone along due to when I've been doing the work and having to just get it done,

 

Rod shims sit between the conrod and bearing housing. There use to be 2 ways to adjust the hight of the piston,

Under the rod

On the cylinder head gasket, there use to only be 2 head gaskets the rest was done from the rod, now new rn have fixed rod and adjust from the head only.

Its a similar scheme on the Gleniffer.  To get the correct big end clearance, the big-end-cap to con-rod joint is shimmed, though the exact measurement procedure escapes me.

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43 minutes ago, jake_crew said:

Its a similar scheme on the Gleniffer.  To get the correct big end clearance, the big-end-cap to con-rod joint is shimmed, though the exact measurement procedure escapes me.

Probably the standard bump clearance measurement procedure in both cases. Build with no or the thinnest shim, put lead wire/multicore solder on the top of the piston above the gudgeon pin axis, fit head,  rotate engine a couple of times by hand, remove head and lead, measure the squashed lead and then use that to work out the required shim thickens. I suspect that if there is no liner protrusion you could use a DTI to calculate the block face to piston crown difference.

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9 hours ago, Tony Brooks said:

Probably the standard bump clearance measurement procedure in both cases. Build with no or the thinnest shim, put lead wire/multicore solder on the top of the piston above the gudgeon pin axis, fit head,  rotate engine a couple of times by hand, remove head and lead, measure the squashed lead and then use that to work out the required shim thickens. I suspect that if there is no liner protrusion you could use a DTI to calculate the block face to piston crown difference.

Yes correct.

 

I should have  liner protusion of 0.010"

 

I had no shim in the conrod before but it also then allowed the oil to seal out with a 0.010" shim this should act as a seal and just means I run a very slightly thinner head gasket shim.

 

Edited by billybobbooth
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I've only take a few as was very busy trying to get it all done in the month lockdown,

 

Paint is all 1940s-1950s proper engine enamel paint mid brunswick & signal red all old but new paint. The block will be done the same. I'm very lucky to have had this in the back of a shed. I have enough to do more but as its now unobtainable and nodowt very rare

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