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Discussion Starter · #1 · (Edited)
Hi everyone. My first post on this forum!

I have a SWB '82 model MQ, petrol L28 motor, with what I reckon is a bad case of persihed/worn valve stem seals. Lots of smoke after idling, and with quick pumps of the accelerator. And high oil consumption rates!

I have done a bit of research and found a description of how to do this job without removing the head. But it seems a certain KD tool, a spring compressor that hooks under the cam shaft, is needed. I have only been able to buy the narrowest spring compressor I could find, with 2 jaws instead of three, but I think I will at least need to remove the camshaft to get enough room for it to fit onto the spring properly.

So I am trying to decide whether its worth the trouble to do it like this - having to use compressed air to hold up the valves, and then worrying whether the pressure fails and the valve drops, working over the edge of the car at arm's length from the fiddly job, having to remove the radiator to get the camshaft out of the way, . . .

Am thinking it might be easier to just take the head off and set it up on my solid workbench where I can get a lot closer to the 'action'.

HAs anyone done this job, either way, and might have some thoughts, or hints? I have only worked on pushrod, Holden, motors before, so have not had to worry about an overhead camshaft!
 

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from his post it sounds like he has a petrol, sd33's are pushrod, not overhead cam.

as for the compressed air idea, i believe some people also use nylon rope pushed in through the spark plug hole to stop the valve from dropping into the cylinder. if you can get the rope in there, you may be able to push the spring down to get the retainers out with only having to remove the rocker gear. good luck with it
 

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Discussion Starter · #4 ·
hi mate,im having the same problem with smoke,does yours blow any black smoke at all or is it just white/grey?
With the motor cold, it is white smoke. But I think this is just because its more condensation than oil being burnt. I think that when the oil is cold it is so thick that not much dribbles down past the seals. Then when the motor warms up, the oil thins down, and then the blue smoke starts showing.

I was getting fairly poor oil consumption figures when I first got the car, About 400km per litre! But it gradually improved to about 1200 to 1400 km. I thought this was because the rings were seized up with carbon and sludge, and they might be getting cleaned out with all the long trips I was doing. Maybe, but also probably because I gradually went to thicker and thicker oil. Settled on Penrite 30/70.

But the last couple of trips in the deserts ( between Aselaide and Melbourne, the consumption shot back up to about 1 litre per 300km! Not so bad on the highway, but still only 600 or 700 km per litre. All very expensive and inconvenient. So now I have decided that I need to stop having fun for a while, and do some serious fixing!
 

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Discussion Starter · #5 · (Edited)
from his post it sounds like he has a petrol, sd33's are pushrod, not overhead cam.

as for the compressed air idea, i believe some people also use nylon rope pushed in through the spark plug hole to stop the valve from dropping into the cylinder. if you can get the rope in there, you may be able to push the spring down to get the retainers out with only having to remove the rocker gear. good luck with it
Oops - yep, its a petrol L28 motor.

Yeah bods, I have read about that trick too. But the problem is that apparently you have to make sure the drive chain is wedged firmly so that the tensioner does not tighten up. And also I guess so that the chain does not fall off the bottom drive sprocket, and then you can pull it back tight onto the wrong teeth if you are not lucky.

So I am thinking that means you cannot turn the crankshaft to bring the pistons up to near TDC, which means you are going to have to use a lot of rope in some of the cylinders. Maybe not. Not sure. Or do you just take the wedge out, fit the chain and top sprocket back on, and turn the motor between each pair of cylinders?

And, as I said, how easy/hard is it to be leaning over the edge of the car to do the job. Was thinking I would probably take the bonnet off, and the carby, and somehow climb up onto the bullbar, and fenders. But sounds awkward when you are playing with tricky little collets and compressed springs!

So if anyone has done this job, I would love to hear your thoughts. Did it go well for you? Would you do it differently next time?

Cheers, Millsy.
 

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Take the head off (Don’t forget to wedge the chain) then while your at it you can lap the valves and check head for corrosion especially the rear water gallery. You can then also check the piston to cylinder clearance and bore condition, as if you blowing a lot of smoke or worse using oil its more than stem seals mate, stem seals blow smoke at start up after sitting for a while like overnight and maybe a big puff at the bottom of a hill after coasting you wont actually “Use” f**k all oil from seals alone being worn. Do a compression test first too (Wet and dry) it will tell you if the rings are gone which is likely if your getting smoke and using oil

FYI
A dry test means just crank it as is and take a reading. Low readings could mean bad rings, valve seats, head gasket etc.

A wet test is done after a dry test, squirt a fair bit of oil through all spark plug holes and just free crank motor to spread the oil in the cylinders then do another compression test. If the readings are heaps higher than the first test then you can be sure the rings are worn as the oil will temporarily seal the worn rings giving the higher reading.
 

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Discussion Starter · #7 ·
Thanks for that 270win. All makes good sense!

Have not done a piston to bore clearance measurement with the pistons still in the motor. ( Years ago I owned a set of piston micrometers, and also a set of bore micrometers, and took the pistons out to measure them. ) But are you suggesting that maybe a set of feeler guages could be used with the pistons just wound up to the top of their stroke?

Am thinking that since the head is off, I might as well drop the sump and remove the pistons and least give them some new rings and bearings. But I guess it would be nice to know if the pistons need replacing too!

And if I do take the pistons out, can you just have a helper feeding the timing chain by hand, maintaining enough tension to stop the chain tensioner from tightening up, as you rotate the crankshaft to remove each pair of pistons? Or do you need to take the front cover off and mark the chain and crank sprocket before letting it all go loose?

Thanks, Millsy.
 

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Discussion Starter · #10 · (Edited)
if your going to pull the motor down why not replace chain and tensioner? its not too hard
I think I might actually end up just doing a complete rebuild. Spoke to a local reconditioner today and he gave me a quote of just over $600 for all new parts for the block ( pistons, rings, bearings, timing chain, tensioner, chain guides, all gaskets and seals, and welsh plugs ( an engine 'kit'). I thought that sounded like good value!

And when I asked him about doing a complete overhaul of the head, including hardened valve seats for the LPG, he said anything between $300 and $600, depending on if there is any welding to be done to fix cracks or water gallery corrosion.

So for between $900 and $1200, and a bit of fun time with the spanners, I could have a nice new motor! So will pull it apart, measure the bores, ( hopefully no need for a rebore ), and crank journals, and decide whether to go for the 'kit' or just buy the parts needed. Probably go for the kit.

And with a bit of luck he will answer a few queries about any tricky bits. He already gave me a good explanation about how to deal with the timing chain. And he told me that you can buy a ready made plastic wedge from the speed shop to chock the chain. So that saves making one up.

So wish me luck please, and I will let you know how it all goes!
 

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Millsy,

You can not have someone hold the chain and turn the crank the tensioner will pop out guaranteed.

Don’t buy a wedge they are piece of piss to make, I can send you a sketch of the size required if you need.

You would want to check piston to bore clearance with a feeler gauge (I have the spec somewhere) but you would do it at middle or bottom of stroke as the top of the cylinder has a lip formed from the top ring so top of stroke would give a false reading. You will see what I mean if you take the head off. You would only be able to check 4 cylinders without turning the crank but you would get a good idea still.

If your head was in good condition and the piston / bores where pretty good you could get away with lapping the valves new stem seals and a ring kit, don’t forget you need to give each cylinder a quick hone or the new rings will glaze and they wont bed in. Probably cost you $150 - $200 for a valve regrind kit (Basically all gaskets and seals from the block up) and $80 -$150 for a ring set.

$600 seems dam cheap for all the parts you listed even at trade cost, I would get that in writing before getting to far into it mate, find out the brands too you don’t want crappy China made stuff.

If you are interested I recently got rid of a couple of old 240K Datsuns I had for years, one of them had an L28 in it that I was going to rebuild the buyer did not wont the motor or rebuild kit so I have this to get rid of.

Full Monotorque Gasket & seal set
Standard diameter ACL big end bearing set
Standard diameter ACL main bearing set
Endurotec 1st diameter rebore piston and pin set
Hastings USA full ring set to suit

Just that listed above cost me over $1000 as they are all good brand components.

Also an L28 motor from a 280ZX – this motor has been modified to suit a 240K as 280 has a rear sump and the 240 has a front sump so oil pick up has been turned 180 deg and an extension welded to it and the sump has a dip stick welded to the side as I did not want to drill the block. I don’t know which way a Patrol goes but you could mix and mach your sump oil pick up to suit if need be.

This motor is stripped down and is in bits, it needs to be bored and honed aprox $250 then the new pistons pressed on the rods aprox $10 each. The head needs welding as it has corroded water galleries (common fault). This is the fuel injection head and has the biggest valve set of any L series motor.

If you or anyone else for that matter are interested PM me and we can talk price.

Oh I also have a complete set of triple 40DCOE side draught webers for L series 6 cyl ready to bolt straight on but they prob would not suit a 4X4, they make the motor go real hard though and they look pretty tuff too.
 

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Discussion Starter · #12 ·
Looks like you love your Skylines. Is that what the 240K is?

Thanks for all those hints. Yeah, I was going to buy another 'de-ridging' tool. Had one back in the '70's at a country school, where the kids were 'doing up' old Holden grey motors that we collected from the farmers junk yards in the 'back paddock'. And also need to get another honing tool.

About the piston to bore clearance. Would I be right in saying that this feeler gauge test, if it is above specifications, won't really tell whether it is the piston that has worn, or the bore? And do you lever the piston right across to one side of the bore, and then push the gauge down the enlarged space on the other side? Or does the piston just sit perfectly in the middle. Am thinking that the rings are just going to compress, or the piston will rock on the gudgeon, if you don't push it hard up against the cylinder wall.

So yes please, I would really appreciate the clearance specification, and also the dimensions for the chain wedge.

Here are some of the prices and brands of the parts he quoted -

- HYPATEC pistons EPR1500 ( whatever that means ) $245
- Cast rings M-86.00 - 0.00 - 2 - 2 - 4 $80
- Con rod bearings $42 Main bearings $67 ( I might not bother with mains – the engine has only done 260 K )
- ENDUROTEC timing kit ( new chain, guides and tensioner ) $56.
- Full gasket set $187 ( does not give brand, but I hope it is Monotorque )

Thanks for the offer on the parts, but I think I might do the 'right thing' by this chap and buy the parts from him. That way I feel he might be happy to answer any questions I might have. Apparently he builds race motors for the entusiasts. He has a huge workshop with machines all over the place. Looks like a neat, well set up business.

I also have my eye on an old Patrol that I am told has a recently reconditioned cylinder head. So if I can get that vehicle for $350, which from previous talks 6 months ago is a good chance, I will have a spare parts car as well. And another eye-sore in the front yard unfortunately. So will take the head off first and see how it looks before I make any decisions.

Cheers, Millsy.
 

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No worries mate.

Basicly if you can fit the feeler in between piston and bore that is the gap.
My book says piston to cylinder gap is 0.025 - 0.045mm which is pretty close and I dont think you will get that, the same manual though says maximum cylinder diameter and minimum piston diameter and the diferance of the two is 0.085mm so I would say 0.085 is still in spec, realisticly with a well used motor i would be happy with 0.20 or even 0.30 I have seen a lot worse like around 0.5 that still go alright and dont smoke too bad.

Attached is a scetch of the wedge you need, basicly hammer it in hard and then you can take the cam gear off.

Good luck with the rebulid, L motors are easy mate if you get stuck on anything send me a PM happy to help, I have rebuilt plenty of them over the years.

Cheers.

P.S. Yeah the 240K Datsun was an early Skyline known everywhere but here and the UK as the C110 Skyline, had one since I was 17 (Long time ago) but was time to make room in the yard so they had to go.
 

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Discussion Starter · #14 ·
Thanks again 270win. You have been a great help! And thanks for the offer to pick your brains when I need help! That drawing will come in handy.

Have just been reading the Patrol manual and my old "Repco Engine Service Manual". It looks like the feeler gauge piston clearance test is done with the rings removed. It seems to be the test if you have not got micrometers to measure the pistons and bores accurately. The manual says that if you use a .04mm feeler gauge, the extracting force as you pull it out from between bore and piston, on the thrust side of the piston, must be between 0.2Kg and 1.5kg. So as you say, different specs from different sources, and looks like they are on the conservative side for all practical purposes.

So it will be interesting to see how it measures up. An American posting on the Web about rebuilding the L28 talks about how tough the L28 cylinder liners are, and that they hardly ever need reboring. So with a bit of luck I am hoping to still see some of the cross hatch pattern, and that would confirm that there is hardly any wear in the bores. Then if the clearance is too large, I just have to put new pistons in without having to pull the block out for a rebore.

It would still be good to pull the pistons out and clean them up even if the clearances ( as measured down to the top ring ) look OK. Clean out the ring grooves, and any oil control holes in the bottom ring groove. And of course put in a new set of rings and do the honing.
 

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Hi everyone. My first post on this forum!

I have a SWB '82 model MQ, petrol L28 motor, with what I reckon is a bad case of persihed/worn valve stem seals. Lots of smoke after idling, and with quick pumps of the accelerator. And high oil consumption rates!

I have done a bit of research and found a description of how to do this job without removing the head. But it seems a certain KD tool, a spring compressor that hooks under the cam shaft, is needed. I have only been able to buy the narrowest spring compressor I could find, with 2 jaws instead of three, but I think I will at least need to remove the camshaft to get enough room for it to fit onto the spring properly.

So I am trying to decide whether its worth the trouble to do it like this - having to use compressed air to hold up the valves, and then worrying whether the pressure fails and the valve drops, working over the edge of the car at arm's length from the fiddly job, having to remove the radiator to get the camshaft out of the way, . . .

Am thinking it might be easier to just take the head off and set it up on my solid workbench where I can get a lot closer to the 'action'.

HAs anyone done this job, either way, and might have some thoughts, or hints? I have only worked on pushrod, Holden, motors before, so have not had to worry about an overhead camshaft!
You don't need to do that.
Your must take the cam shaft off first.
Remove the spark plugs.
Turn the crankshaft by hand to get top dead centre on the valve you need to replace.
Get your self a matching tread to fit the spark plugs thread. Air compressor will help if you have one.
You need to compress the piston chamber first stops the valve from dropping in the piston and then compress the spring and remove the stem seal. Make sure the compressor stays on until you fit new seal.
Cheers
 

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You don't need to do that.
Your must take the cam shaft off first.
Remove the spark plugs.
Turn the crankshaft by hand to get top dead centre on the valve you need to replace.
Get your self a matching tread to fit the spark plugs thread. Air compressor will help if you have one.
You need to compress the piston chamber first stops the valve from dropping in the piston and then compress the spring and remove the stem seal. Make sure the compressor stays on until you fit new seal.
Cheers
I sure hope it took old Millsy less than 12 years to replace a set of valve stem seals.
 

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I sure hope it took old Millsy less than 12 years to replace a set of valve stem seals.
He should just about be done if he did one valve per year.
 
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Thanks for that 270win. All makes good sense!
Am thinking that since the head is off, I might as well drop the sump and remove the pistons and least give them some new rings and bearings. But I guess it would be nice to know if the pistons need replacing too!

And if I do take the pistons out, can you just have a helper feeding the timing chain by hand, maintaining enough tension to stop the chain tensioner from tightening up, as you rotate the crankshaft to remove each pair of pistons? Or do you need to take the front cover off and mark the chain and crank sprocket before letting it all go loose?

Thanks, Millsy.
Doing just valve seals with the head on is like cleaning your teeth through your bum (but only your top teeth - so what's the point ?)
Unless the L28 is under 150,000km I'd suggest remove the head, de- carbon, and lap/cut the valve seats.
Once the head is off, have a look at the tops of the pistons - crook rings will be clean/wet around the perimeter of the piston top by about 8mm or more.
If you're doing rings and big ends, and you've got less than about a 10 thou ring ridge, just scrape out the ring ridge with a bearing scraper and give the bore a hone. A bit of piston slop isn't the end of the world. (more than 10 thou and you'll need a re-bore)
Chuck on a new timing chain and you're good for about another 200,000km +
If you can get the sump off in the car, you don't even have to pull the motor out. (it's actually easier in the car than on the bench)
Haven't done a L28 MQ, but these are just general tips for a quick , cheap refresh
Don't fret the valve timing - it's not rocket science. Just put # 1&6 on TDC, set the cam to have #6 valves rocking, and fit the chain without slack on the pull side. Turn engine 2x rotations and re-check #6 is still rocking on TDC. (I don't even bother using timing marks anymore unless it's a fine gear drive on a diesel.)
 
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