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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Music to my ears

http://www.woodburnguitars.co.uk/Clara/NewHead.wmv

Got it all up and running this evening. Turned the engine over without the spark leads attached just to get the juices flowing then re-attached the leads and she started on the first turn of the key.

Oil pressure started at 40 and after 10mins at idle was holding steady at 20. No leaks detected so far. Sounds fine at idle. I didn't want to risk a run on the road as it was 8.30pm by the time I got to this stage. I'll probably have to wait until the weekend to get her out on the road. Still need to re-install the front grill and replace the number plate anyway.

I'm very pleased so far. Fingers crossed for the road test.
Stuart K

oil pressure is very low.... a good A series is 80 running cold and 40 at tickover.
David (davidDOTsmithAT stonesDOTcom)

>>> oil pressure is very low.... a good A series is 80 running cold and 40 at tickover. <<<

I got the idea Stuart was talking about idle at tickover only; starting at 40 cold and decreasing 20 when hot. His numbers sound okay to me, unless I'm misunderstanding something. Starting at 80 psi at cold idle sounds a bit abnormal.

-:G:-
Gryf Ketcherside

80 is indeed verry high
but can just mean the oilpressuere release valve is to tight

between 20 and 40 is a bit low but not a real problem
again it can be dow to the pressure release valve spring being to loose in this case

my rebuild enginen has 70 cold and than between 40 and 60 hot (dependent on the revs ofcourse)
Onno Könemann

Pressure was at tick over only. I only got to start the engine up and leave it running to get up to temp and check for leaks (I replaced all the radiator hoses at the same time). No revving, no road driving. Haynes said 20 was spot on so I was happy until you burst my bubble!

What figures should I be looking for under normal driving conditions?
Stuart K

I agree with David.

When started from cold, using 20-50 or 10-40 the oil pressure should be >60psi, whether at idle or revs - with revs it should open the relief valve at around 70-80 psi.

When hot (and I don't mean idling on the drive, I mean after say 15 mins at 70 mph) you should see >50psi at revs (usually >60psi) and >20psi at idle.

10 mins idle in the drive might heat the water, but it doesn't heat the block/oil to 100C+. When properly hot (100-110C), your oil pressure may be half your current reading.

Is the engine a new build? Then I'd suspect the oil relief valve not seated correctly and oil (pressure) is leaking past. Or your main bearings are wrong size, or something similar that needs immediate attention.

Sorry to be a bearer of bad news.

A
Anthony Cutler

Not a new build - was trying to avoid that - just a new head and gasket. Come to think of it, I have no idea what oil is in there as I haven't changed it. It is very clean. I suspect the PO changed it just before sale. Might be worth my while dropping the oil and putting in fresh anyway. I think I'll replace the pressure relief spring whilst I'm at it and cover all bases. Silly question but do I need to have drained the oil to do that?

What is the recommended oil these days? <-can of worms question?

Stuart K

Agreed the pressure will be low when the car gets hot. Assuming this is the same engine as before but with a rebuilt head I think this was the risk you elected to take. If you havn't changed the oil and filter it's worth doing now - as would be adding a can or two of Wynns or STP which should see another 5 - 10 Lbs oil pressure across the range. This will at least prolong the inevitable, and may even bring it within range.
On a brighter note your guitars look simply fantastic, and anyone with the skills and precision to create a beautiful instrument like that will find rebuilding an engine no trouble at all.
f pollock

In my limited experience, people who hope their low oil pressure is due to a slack spring are usually disappointed.

Having said that, the thing to do is get it hot and see. Stuart - you did fill with oil to the correct level, didn't you? 20W50 is what you want.

Below 20 at hot idle would be rebuild time for me, but I know plenty of people who've soldiered on happily - accepting that the journals will be eliptical when they do get round to the rebuild.
Nick

Agreed with the comments re guitars. I use a Gibson Les Paul Custom mostly... but have several acoustics and electro-acoustics around the house in case I need to suddenly play something.

Nick - you are probably right re the spring/seating not often being the cause of low oil pressure, but worth a check.

Other common causes of low oil pressure are:

- faulty gauge (how to tell?!)
- worn mains and big-ends (can replace centre-main and biggies with engine in situ; done this several times as band-aid, with reasonable lasting effect!)
- worn pump (engine out job, since it's behind the back-late

It's hard to tell re spurious noises from the sound-track... engine's always sound tappety on audio files.

You don't need to drain oil to re-seat spring/valve.

I'd stick in a 20/50 (Halfords?) and see if there's any difference. If not, and the engine isn't giving any bearing hammering (listen when properly hot accelerating in top under load between 30 and 50 mph), then I'd stick some Wynns or similar in there, avoid long motorway journeys and high rpm (say >5K) and enjoy the car for the summer.

A Series re-builds are not a big deal. You'll have plenty of advice on this site. I've built an engine from bare block (back from re-bore) in an afternoon.

A
Anthony Cutler

Thanks. The oil is at correct level but it is the oil put in there by the PO so is an unknown viscosity/brand. I'll do an oil change and for good luck change the pressure spring. It was always suspect from the outset that the head wasn't the only problem so I was prepared for this. What I was hoping was to get an engine I can run over the summer and go for a rebuild or engine swap in the Autumn. If I run at low pressure I presume I'm risking heavy wear as the engine does not get lubricated correctly?

Thanks for the comments re the guitars. They are the reason I'm trying to save time on the engine. Got 2 guitars half built and need the time to get them finished. I don't really have time (or clean workspace) for an engine rebuild. So little time, too many hobbies!
Stuart K

Stuart, you shouldn't have mentioned oil pressure, all we've done now is worry you (sorry). Suggest you change oil & filter, use a 20/50 like Miller's classic or Duckhams and just drive it and enjoy it...
David (davidDOTsmithAT stonesDOTcom)

Agree absolutely with David. Paul H (are you there, Paul?) ran his Sprite on several summer tours with an idling oil pressure of zero. He said he wouldn't worry so long as it didn't drop any further.
Nick

and you never know how accurate the gauge is. I had mine checked and it was reading 10psi low………
Rob Storer

Nick said "Paul H ran his Sprite on several summer tours with an idling oil pressure of zero.He said he wouldn't worry so long as it didn't drop any further."

Thanks. That made me laugh!

Onwards and upwards. Been out to get some oil this lunchtime.
Stuart K

i have to agree with the motto

just drive it!
Onno Könemann

just checked out the guitars
cool
nice to see the gladny patronen (dutch way) being used in guitars two

i did an intern ship with a double bass builder and he was realy in to tuning the frequency of the front and back plate of a double bass
even the neck and tail piece were tuned using knock tones and tone generators and analysers
http://www.diegesdoublebass.com/

verry nice to do as a hobby hard work to do as a living
Onno Könemann

same here....at least you dont have to worry about it running to high of psi, so that should provide some relief

Prop
Prop

Hi Onno, nice basses there. Yes as a hobby it is fun but to make a living from it is very hard.
Stuart K

Stuart,
You mention that the oil "is very clean". This could suggest that it is a (low-viscosity?) synthetic which could explain the slightly low pressure. Synthetics don't quickly discolour like a "proper" mineral oil.

It is also a mistake to think that high oil pressure is necessarily a good thing. Excessively high means both a lower rate of flow - so less heat removed from the bearing hot-spots; and also more heat generated by the compression of the oil film.

As long as pressure doesn't drop below 20 at idle and maintains something around 60 ish at 3,000rpm when hot then I would just accept that that is just a well bedded-in engine.

Guy
Guy Weller

Well I changed the oil to 20/50, put in a new oil relief valve spring and took advantage of the sun to take her out on the road for some top down fun. I discovered several things:

1. I'm going to need to invest in a pint of sunblock to cover my poor bald head

2. What a joy it is to be out on the road in a midget. Haven't had so much fun in ages!

3. It gets really hot in the foot well, is this normal?

4. The rev counter needle sticks. Probably the cable?

5. The clutch whines sometimes when sitting at idle.

6. The oil pressure is not good once it is hot. I get 40 when cruising at 55/60mph but it drops to almost zero at idle. Shoots straight back up again as soon as I rev the engine or set off. Looks like I need a new unit. Either now or at the end of the summer.

7. It doesn't seem as nippy as I was expecting. Presume this is because the engine is knackered.


I am resolved to rebuilding or getting an exchange unit. This raises a few questions. I could just swap like for like and get a 3/4 1098 engine or I could spend a bit more and put in a 1275. I know what most people will say but a 1275 is difficult to source and will cost me more. Assuming for a minute that I can get a 1275 unit what else will I need to complete the swap. I think I may need a different distributor. The carbs will need rejetting - is this a case of getting different needles or do the jets need fiddling with? Will I need a different flywheel? Will my radiator be ok or will I have to upgrade that? Is there anything else I haven't thought of?? The additional extras may be what limits my choice as I think it could run quite expensive to go to the 1275 option.

All comments gratefully received.



Stuart K

1 since i've got a midget i always carry some

2 Jeah!!!!!

3 close the heater vent and it will become better but i did melt a pair of shoes last years trip to lemans

4 do you have a mechenical ?or a electronic?

5 don't worry about that

6 at the end of the summer it is already going to be a rebuild so who cares how bad it gets

7 1098's can be verry nippy certanly when still fitted with the original 4,22 diff

If you want to swap the time is now
But a 1098 with a decent head sw5 cam and a solid botom end can be verry mutch fun as well.

the carbs will be yets and needles but rebuild the as you are at it
nothing worse than a new engine and bad carbs

The distributor will work and certanly if you are going to modify a 1275 it is just as good as the 1275 one!
The curve will not perfectly match your engine anny way but it wil work and you can always play with the springs


Onno Könemann

A few comments from me. First, torque the head down, readjust the valve clearances and check the timing and carburation are correct. This at least optimises what you have. If the engine is not showing undue signs of mechanical distress with smoke and noises, add the can of Wynns, the sunblock and run it through the summer. The cheapest and easiest rebuild option for you is going to be an exchange bottom end with your existing head, carbs and ancillaries. With a new clutch assembly and release bearing you could probably do it for a ballpark figure of around £1000. If you go the 1275 option it will entail more flaffing about and another £500 to cover sourcing a second hand block, and also a provision for a rolling road set up, as the head carbs and ignition off the 1098 will be wrong. So back to Rod Taylor and another £150. But this will also be true of a modified 1098 or any hybrid engine that changes the basic standard set up.
f pollock

Hi, the rad you have(vertical flow?) should be ok with a 1275 as the early 1275's used this rad until the crossflow rad came in.

I have a mildly tuned 1275, bored +30 and cooling has never been an issue.

Mark
Mark Whitmore

i have a hot 1380 with verticalflow rad and even that is no problem

but as i have forgoten to mention above if you go the 1275 route you will need a matching flywheel the 1098 one does not fit
Onno Könemann

Can you pull the oil pan from a Sprite without removing the engine like you can with an MGB?

If so, since it would be so easy, I would be tempted to throw a new set of rod bearings in it and see if that improves the oil pressure.

Charley
C R Huff

You can remove the sump with the engine in situ, its not difficult at all.
A D Smith

As I said earlier, it's easy to replace the centre main (under the most stress) and all four biggies by dropping sump.

I've done this several times to engines as a 'band-aid' and in every case engines have done seveal more years good service...

A
Anthony Cutler

Bear with me then. Looking at my manual I think I can see which one is the centre main bearing. So I drop the sump. The centre main is the central bearing on the crankshaft. When you say replace it I presume you mean I have to undo the main bearing bolts and remove the lockwasher and bottom half of the big end. I'm guessing that I then have to remove the bearing shell - top and bottom - and these are the bits that have to be replaced together with the thrust washers? Is that as easy as it looks or does it involve a lot of swearing? Can I get to the other bearings as well or is it only the centre main?

Went out in her again today. The original rattle that I first asked about is still there when under load. Seems to me the head gasket blowing was something that happened after I got the car and was just a coincidence. I think the rattle almost certainly is the bearings.
Stuart K

you can do all four big end bearings, and the centre main bearing, easily from underneath.
David (davidDOTsmithAT stonesDOTcom)

Sorry Anthony, you did cite that earlier, but this is a long post, so it is worth repeating.

Stuart, yes it is dead easy and just like you have described if you have done it before. If you have not, it might be a bit daunting.

Also, watch your terminology. The main bearing has no big end. The main bearings are the main bearings, and they hold the crank to the block.

The big end bearings are the rod bearings, and they connect the connecting rods to the crank. They go up and down while the engine is running, and the main bearings do not go up and down.

You can replace all four rod bearings (big end bearings) once the oil pan is removed. The ability to replace the main bearings in situ depends upon the engine. From other's advice, it sounds like you can only replace the center main bearing, which it seems you have identified correctly. In some engines, you can replace all of the mains in situ. If you have trouble removing the upper main shell (bearing half) you can slip a roofing nail in the oiler hole of the crank and roll the old shell out by turning the crank.

Charley

C R Huff

The main bearings at the ends of the crank can't be replaced as e.g. there are bolts from the end-plates into the bearing cap - and you can't get to these bolts with engine in place.

Undo 2 bolts on the centre cap, and you can tap it and release it. Check it's a std size, (or oversize if crank has been ground; do same size check for b/e's as well; see markings on shell).

A new shell easily replaces old worn shell in the cap. It's a little more tricky to replace the top shell. You need to push (use say a small screw-driver or strip of ally) the bearing round the crank - pushing the non-tang side. When it's moved round to cover the whole journal, you can peel it off. Sliding the new one in is the reverse operation.

Big-ends can be replaced 2-at-a-time by positioning the crank so you can get a socket on the nuts.

It goes without saying you should ensure caps are put back onto the same journal in the same orientation, and torqued. When the job is done, the crank should rotate as before.

You will have removed the plugs to make the crank easy to turn. When the sump's back and oil replaced, turn the engine over to build up oil pressure; then replace plugs and start.

Be prepared to have the odd oil drip from the crank find the centre point of an eye-ball; they are designed to do this.

Whole job is around 90 mins when done carefully and methodically (as any job in the guts of the engine).

BTW - this is the first job I ever did on a engine (apart from plugs and points). At that time, I'd never seen the inside of an engine, but it was all there as expected; 1098 CC engine of 1965 Midget in 1975.

A
Anthony Cutler

Thanks, clear now. I'm so tempted to do this as I enjoy the work and I'll be able to say I fixed it. Nagging doubt in my mind that there could be other problems that won't get fixed if I go down this road and once I've committed to spending the money on the centre main and big ends if the problem isn't fixed I'll have to go for a rebuild rather than a recon unit or I'll have wasted a lot of cash. I don't have a problem with taking the engine out - I have a crane etc - it is more a time commitment thing and I'll have to create a clean workspace. My garage is tiny and in order to work on an engine I have to park the car half outside the garage with the backend out in the weather.

One question if I go down the do it yourself route- in order to get reasonable access I'll have to have the car up on axle stands. Is it easy enough to turn the crankshaft pully from underneath to rotate the engine if the plugs are out. I had enough trouble from up top when the radiator was out. Not exactly easy to get at are they? Would be a lot easier if there was room for a spanner to crank the pulley round.
Stuart K

Stuart,
When mains and big ends wear and oil pressure begins to drop, initially almost all of the wear is in the soft metal of the replaceable bearing shells. The crank itself usually hardly wears at all initially. If left, the shells wear through to the backing material and then the crank starts to wear badly and would need a regrind. So doing this job early is definitely worth while. The shells themselves are not expensive. When I had a 1500 Midget I used to replace mains and big ends as a routine service item, every 24,000 miles.

The other thing worth checking when the sump is off is the crank end float as the C - shims to correct this are also easy to do.

Guy
Guy Weller

I replaced the shells 3 times on BRB (with Aseries; once in situ, and twice 'out' - the last time was a 'proper' rebuild with re-bore, oil pump, cam bearings, cam, chain,...). The crank was in perfect condition - as Guy indicates.

I treat replacing the shells as a standard measure when the engine is out for clutch etc; it doesn't add much to the cost and time for this job.

I forgot to mention the thrust washers... I did them once in situ; so the upper 2 must be 'round' segments and you can squeeze them round the crank in the same manner as the shells, but in a different plane of course. Taking them out is easy as there is free play. I'd put the front one in first and have someone press the clutch to move the crank forward to do the rear one... this is likely to be just a little more tight (but doable). The lower ones have a tang that slots into the centre cap. Very obvious when you see it. Don't forget to fit with the steel side next to the block...

It should be said that working upside down in a slightly confined space with arms upwards is not the most relaxing environment. Due to the nature of the job, the key is to take your time and make sure each step is done exactly right. There aren't many nuts and bolts to worry about - it's not that kind of job; use extra care to make sure everything is put back right; and check again until you are sure. [I visualise the job sitting down with the parts in my hand; then visualise it in position, then do it; and then go back over it in my head as a final check before I move on; that's a bit careful but 'do the job once' is my motto... I guess not eveyone is as paranoid about these things as me!]

It's easy to turn the engine over from underneath - sometimes you'll need a small length of wood or similar lever to give you a hand... there is a little stiction that makes the initial movement a little harder at some points in its rotation.

I prefer to stand the car on wooden blocks under the tyres... this gives a better feeling of security and more space than axle stands under the front chassis rails. (Handbrake on; in gear; chock the rear wheels for belts, braces and 2 pairs of pants.)

An inspection light by your shoulder is a big help.

A
Anthony Cutler

get a cheap led head lamp
it is lovely to have light where ever you look
Onno Könemann

Belts braces and 2 pairs of pants. Ha! I'm the same. When ever I'm working under a car I have it chocked, handbrake on and even if I'm using axle stands or ramps I still leave a jack under there too if there is room. I'd love the luxury of a proper ramp or a pit.
Stuart K

I've reached a decision. No more annoying questions. I priced up the parts for bearings and thrust washers and it is not an inconsiderable sum. If this was a car I had had for some time and knew the history of I would probably do the bearings BUT I don't know anything about this engine's history. So far with this engine:

it has had the wrong head on a block that wasn't machined to take it

it is painted gold which may have been a whim but may have been a recon in the past

I've found manifold nuts which were barely finger tight


Therefore I think for peace of mind and to save time and effort I am going to put in a new unit. I've also decided to keep the old girl original and replace like with like and keep to a 1098. Hopefully I'll be back on the road fairly quickly with a straight swap.

Thanks for all the advice so far. No doubt I'll be asking plenty more questions about other items - like why my rev counter is sticking. I'll get me coat....
Stuart K

Worth a look http://www.morrisminorspares.net/shop_item.php?ID=3625
f pollock

first the engine?
or first a summer of driving?


Onno Könemann

This thread was discussed between 09/06/2009 and 15/06/2009

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.