Leyland 498 Rebuild - a few questions

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Woody3
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Leyland 498 Rebuild - a few questions

Post #1 by Woody3 » Sat Apr 28, 2018 12:49 am

Bit of background. 4/98NT in a 3CMk3 - was knocking (top end) on cylinder 1 or 2.

Currently in a stripped down state. I've had the head skimmed (12 thou had to come off) and the valves have been reseated. Looks like one of the previous owners took the thermostat out, which usually means the engine will run cold constantly, but due to the design of the 4/98, removing the thermostat means the water just circulates around the engine and not into the rad - or so I've been told.

I'm now at the stage where I'm putting it back together again and I'm just after some pointers (never done any in depth engine work before).

1) One of liners needed to be replaced. What's the best way to insert the new liner? Do I use any sealant around where the two seals meet the liner? How do I ensure the seals won't push out when I put the liner in? I was thinking of putting the liner in the freezer so it should slide in easier. I have done a dry fit and no shims are required (did the 2p trick).

2) Do I have to hone the new liner once it's been installed?

3) I'm putting new rings on the piston that has the new liner. Does anyone have any details about how to clock/gap the rings?

4) I'm also replacing all of the big end bearings. What are the torque settings for the bolts that connect the conrod/bearing cap to the crankshaft?

Any input on the above or any other hints and tips would be much appreciated.

Thanks!


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Re: Leyland 498 Rebuild - a few questions

Post #2 by agrimax » Sat Apr 28, 2018 10:36 am

Make sure the oring grooves are exceptionally clean. Some say to use a little soap,some say vaseline,others say not to use any petroleum based products. Personally,I use a little instant siligasket(usually the black stuff from Kent Industries or similar). It means if there is a bit of pitting in the groove the siligasket will seal it up.It's a bit messy but smear the oring lightly and again when it's fitted. This will also lube the orings sufficiently for the liner to pass through. Piece of good hardwood on the top and tap the liner home. New liner shouldn't need honed. Ring gaps just need spaced at different intervals around the piston.
Torque settings are here.......
https://www.thenuffieldandleylandtracto ... ttings.PDF


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Re: Leyland 498 Rebuild - a few questions

Post #3 by Woody3 » Sat Apr 28, 2018 8:44 pm

You're a star Agrimax - thank you very much!


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Re: Leyland 498 Rebuild - a few questions

Post #4 by Woody3 » Sat May 19, 2018 11:38 pm

Just to update the thread, I'm now starting to put her back together again.

I've had the cylinder head reskimmed and valves reseated
Installed new big end bearings
A new nozzle for one of the injectors
A new liner and a set of piston rings to suit


Now, I'm going to post this next bit in the wanted section, but on the off chance, does anyone have a spare "short" cylinder head bolt to suit the 4.98NT or know where I can source one? I've got one bolt that's got damaged threads.

Thanks!

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Re: Leyland 498 Rebuild - a few questions

Post #5 by modelman093 » Sun May 20, 2018 5:36 pm

Theses days most rings come ready gapped but use an upside down piston to push each one about an inch into the bore and check the gaps with feeler gauges.


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Re: Leyland 498 Rebuild - a few questions

Post #6 by agrimax » Sun May 20, 2018 11:53 pm

modelman093 wrote:Theses days most rings come ready gapped but use an upside down piston to push each one about an inch into the bore and check the gaps with feeler gauges.


He means the position of the ring gaps when installed on the piston......

I don't know the thread size other than it's likely UNF but are there any engineering firms nearby that would run a die on the damaged bolt?Or maybe it's too bad....... Failing that https://www.charnleys.com/ should be able to help.

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Re: Leyland 498 Rebuild - a few questions

Post #7 by modelman093 » Mon May 21, 2018 12:26 am

He means the position of the ring gaps when installed on the piston......


Really?
This side of the water the use of the word "clock" implies measuring. By all means, stagger the gaps to avoid initial blow by, avoiding positioning a gap on the thrust side, but in use, they will move around anyway.

Thermostat. As the OP says, the removal of the thermostat may result in the failure to direct the majority of the coolant around the radiator which is sometimes assisted by using a shielded thermostat that partially closes the "quick warm-up" passage around the head and directs the flow to the rad.


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Re: Leyland 498 Rebuild - a few questions

Post #8 by Woody3 » Tue May 29, 2018 5:24 pm

Thanks chaps.

Yes, I did mean how to space them around the circumference of the piston, having never done it before, I wasn't sure what to do.

Anyway, pistons are all in, cylinder head is all torqued up.

All going good - putting the fanbelt back on and the stubby prop/driveshaft falls off from the hydraulic pump. The UJ has disintegrated and has worn the fixed yoke :doh: I'm now thinking this may have been the reason why it was knocking!

So, does anyone know where I can source a used propshaft? Or if anyone knows of the part number, that would be much appreciated.

Sorry to be a pain - it seems like I solve one problem and then another arises!

Thanks again!


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Re: Leyland 498 Rebuild - a few questions

Post #9 by topkit » Tue May 29, 2018 9:39 pm

You could try Simon Vicary jcb parts or Rusty Parts both have websites under those names and both are always very helpful.


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Re: Leyland 498 Rebuild - a few questions

Post #10 by essexpete » Wed May 30, 2018 9:27 am

Yes I would try one of the dismantlers and Vicarys have been helpful in the past. If a replacement has been sitting around for a few years it might pay to replace the uj centre.


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