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MG Midget and Sprite Technical - Engine Knock (1500)

Hi Guys,

Just fired the engine up after a couple of years sitting idle and there's a bit of a knocking sound resonating from either the block or the head. It idles fine and i can't see it making any practical difference however it certainly sounds serious. The engine was rebuilt a couple of years ago with all new main bearings, big bearings, little bearings, piston rings, cam shaft and timing chain (duplex) so im not sure what could be causing it.

Any thoughts?

Cheers,

Jamie
Jamie Watt

Many 1500s make a knocking noise until the oil pressure builds up which is due to slight main/big end wear and empty oil galleries and filter and lying unused, but can go on like that for ages without problems as long as the pressure is good while running.
Yours can't have had much running since the rebuild, was all well when it was first restarted?
JB Anderson

Have you thought of converting to steam? You appear to have the pedigree. ;).
Lawrence Slater

I'll run it when i get home tonight and see what kind of oil pressure i can reach. I can't remember any knocking when it was first rebuilt but then i can't remember what i did yesterday let alone 2 years ago...

Have often thought of playing on my name for fame and riches but the "James Watt" brand doesn't carry much weight these days :(
Jamie Watt

Jamie,

where abouts in Grampian are you? I am sure you told me but like you I have a memory like a gold fish! if you are ever about in Aberdeen and want to listen to another 1500 for reference then give me a shout.

or if you just want some help or to chat or whatever, also welcome.

Malcolm
M Le Chevalier

Does it go away? Mine rattles for 2 seconds or so then as the pressure comes up the noise disappears. I'm in the habit of cranking it 10 or so times with the choke closed
to bring up the oil pressure. Maybe dodgy oil or the pressure relief valve is suspect.
HTH
Cheers
Rod
R W Bowers

Malcolm, long time no speak! I haven't been working on the car for a couple years due to work commitments but im back in action and looking to finish it over winter. I live in Milltimber and it would be great to take a look at your midget to see how it runs. I've got many other questions as well!

Rod - thanks for the advice. Didn't manage to run it up to temperature last night unfortunately but will do so tonight. The relief valve has never been looked at in the 9 years i've owned the car so it's definitely a potential trouble maker!
Jamie Watt

Jamie, drop me a mail on mlechevalier@o2.co.uk I am free most of the weekend if you fancy popping by.

Note: the car is by no means complete, but it does start up and drive. Also, there is no guarantee that I rebuilt my engine correctly :-D

Just for reference if you fire up tonight: I get about 60 psi oil pressure with the engine warmed up and at about 2000 - 2500 RPM.

Malcolm
M Le Chevalier

Just fired her up and checked the oil pressure. 20psi when cold falling to 10-15psi when warm. Sounds bad?
Jamie Watt

Certainly not good by a fair margin. Do you have another oil gauge to double check the oil pressure, before doing more intrusive investigations?

Is that at tickover?
Lawrence Slater

Yeah, that's not sounding too hot!

Jamie, I can lend you a spare oil gauge (if I can find it) it's a bit bashed up but still functional.

Hmmm... So, where to begin. Pump, pressure valve, rockers, big ends, main bearings?

Plenty of 20w/50 in it?

Cheers,
Malc.

M Le Chevalier

Is that at idle BTW Jamie? What about when revved?
M Le Chevalier

If it was OK when it was last in use, then it won't have somehow worn out the bearings whist it was standing unused would it?

So, low oil pressure when it was fine before, suggests something sticking - like the oil pressure relief valve?
Guy Weller

oil and filter change never hurts if the existing oil has been sitting for two years
Nigel Atkins

Jamie i wouldn't be "revving it" to check (apologies Malcolm)
Mine runs 85 PSI when hot at 3500 and 75 at idle, but then the motor is fresh and I'm running 20W-60. I'll probably put it back to 20W-50 next change.
Apparently modern oils don't degrade so much with time but I'd definitely whack some new 20W-60 in her asap
Rod
R W Bowers

Seized PRV prime suspect for me......just change it out and try again. May save a heap of travel down blind alleys.
Mark O

I doubt if the oil would become less viscous when left unused for a couple of years. If anything one might expect some of the more volatile components to evaporate off, making the residue more gloopy. Although I don't know if synthetic oil may behave differently.

But as Nigel says, changing it certainly wouldn't do any harm. Another possibility being that the oil is diluted with petrol which would thin it although I doubt that would drop the psi to just 15. Make sure that you don't ever leave the car standing with the choke knob pulled out. With SU carbs this lowers the jet orifice below the level of fuel in the carb and liquid fuel then simply runs out into the inlet manifold and down through any open valves into the engine. Done regularly, this will dilute the oil. In theory fuel running through the choked down position of the jet could set up a syphon and empty the float chambers completely, so its not an insignificant amount.
Guy Weller

Rod - 85 PSI?! Isn't your PRV supposed to open at 53?

Perhaps if you and Jamie could swap. . . .

Sadly, in my experience, low oil pressure has never been due to a short PRV spring or a stuck-open plunger.

It's still the first thing I'd try, though. I'm still optimistic.
Nick and Cherry Scoop

So much speculation, before the reply from Jamie.

Lawrence Slater

Aye, agreed Rod, sorry, I was in a rush and what I said was not well worded. What I meant was not to go out and rev it as it does sound like something is amiss, but if you have already tried, then what was the pressure at idle/when revved up a bit.

But don't get disheartened Jamie, I would trade you your dodgy engine for my boring bodywork prep any day of the week :-D

Malcolm
M Le Chevalier

Hi guys,

Thanks for all the replies - i never thought i'd be jealous of someone else's oil pressure reading but i guess midgets can have that effect!

I have another pressure gauge and swapped it last night but it just reads the same and increasing the revs doesn't make much of a difference at all. I'll change the oil and filter this weekend to see if that makes a difference. There's plenty of oil in there so im not running low.

A thought - when it was running last night i unscrewed the oil cap on the rocker cover and there was air rushing out of it. It didn't feel like there was much pressure behind it but it's got me worried that i've damaged a piston ring or blown the head gasket. Both of these items are all new but have sat in the engine for 2 years. Does the movement of the rockers and push rods create an airflow in your rocker covers? Having said all that, there are no exhaust fumes or oil coming through which gives me a slight degree of comfort.

As ever, your help is much appreciated!
Jamie
Jamie Watt

changing the oil and filter will allow you to see the state of the oil that comes out and if it has contaminants and/or bits in it

I'd also check at the breather pipes are clear

I doubt if either will give you any rise in pressure but you'll be starting from a better place to sort this
Nigel Atkins

I changed the oil in mine early on but the 'sludge' (the white metal from the bearings) didn't come out much cos it had sort of set at the front of the sump. I took the sump off, fainted, and got on with shell replacement after consulting and gaining some great and patient advise on here.

If you want to take the sump off to look I advise either read up carefully or at least be aware that parts of the sump mate with alloy holes that easily strip.

Some blow by is normal on an engine like this but not sure if you should feel blowing when the filler cap is off.
Dave Squire

PS oil pressure and crank case pressure (blowing) are generally unrelated. More blowing relates to more wear in a burning related part of the engine such as valves and rings and bores.

To ensure my oil pressure was up I did the John Twist extra washer in the pressure relief valve to make sure all was well. Its on U tube, University Motors MG Midget engine somewhere. Nigel pointed me at it over a year ago. Good stuff and good from Nigel.

Basically its a hardened washer (spring washer) added to the seat of the spring before the relief valve body is re screwed on. It can't do any damage as far as I can see.
Dave Squire

Jamie. Now that you've confirmed the oil pressure with another gauge, and given that you haven't done many miles on the oil that's in the sump, I wouldn't waste money -- 12/18 quid depending on your selection -- on new oil. Your readings are so low that it'll make little difference. You've got something else wrong.

Do you remember what the oil pressure was 2 years ago when you started it after the rebuild?

Did you fit a new oil pump?

How much did you drive it after the rebuild 2 years ago?

If you put in new ends, and haven't driven the car much, then I doubt the shells are worn.

Lawrence Slater

Is the oil pump pumping oil? I know nothing about 1500 oil routes, nor how the pressure sender works, so it's probably a stupid question.

But is it possible to prime the pump?
Nick and Cherry Scoop

im wondering if the oil separated esp if the fuel was leaking past the rings.

Btw... you did check the dip stick to make sure there is the proper amount of oil in the sump?

When the engine was built... did the oil galleys get a good proper flush and clean out.

Some guy just didnt fill up the galleys with generic coke a cola for 15 minutes and flush it out with a garden hose did they ?

Hahaha...




Prop
Prop and the Blackhole Midget

It wasn't really run for any considerable amount of time post-rebuild for many reasons but before the internals were refreshed it held about 65psi from memory. I'm going to start by changing the oil tomorrow night (unless I end up I'm the pub) and will report back. From the posts above it looks as though 20w50 is the best option? Synthetic or mineral?

Also, I'm running a single side draft weber carb with the choke disconnected so not sure if fuel has sat in the cylinders or not over the years. Fingers crossed this one can be solved with a good glut of oil!
Jamie Watt

Ps plenty of oil in the sump and the block wasn't cleaned during the rebuild.
Jamie Watt

I still think it well worth checking the oil pressure relief valve. Its very easily to remove and clean out. A small bit of dirt could very easily prevent it sealing and this would give you the low oil pressure at all revs.
Guy Weller

Ok so I need to check my pressure valve now, this is contagious, as pointed out 85 is high but i assumed that high was better than low. This begs the question, is the gauge measuring absolute pressure from the pump or after the relief valve??
Maybe Jamie your pump is cactus?
Cheers
R W Bowers

Guy

You must desist from simplifiying matters which can be made extremely complex on web forums. You take all the fun out of it...

Mark O

LOL O'Mark!
Simple mind, simple solutions!

High oil pressure isn't really a good thing. Not as worrying as ultra-low pressure, but high does have at least 6 negatives that I can think of.
Squeezing the oil takes energy, so saps the engine power.
The high pressure also heats up the oil (end of bicycle pump demonstration).
It reduces the volume of oil passing the bearing hot spots so doesn't cool them as well.
Repeatedly squashing the oil degrades it faster - it wears out.
Excessive high pressure in the oilways will seek out weak joints and encourage leaks.
And, rumour has it that it increases flow to the front chaincase with, some say, dire consequences for oil suction and blue smoke clouds!

Any other "issues" ?
Guy Weller

Right, targets for my weekend:

1) change oil
2) check pressure relief valve is working
3) pray that this fixes the problem
4) have a cup of tea
5) pray some more
6) if the above doesn't help then i'll have to remove the sump and check the pump
7) curse continually for having a face covered in oil after removing the sump

I'll report back on progress as i go along.

Malcolm - got your email, thanks. I'll give you a shout tonight once i've changed the oil and we can coordinate for the weekend.
Jamie Watt

Cool, look forward to it Jamie. Good luck!

I am probably a little odd in that I find any job that involves lying under the car (like sump removal) quite pleasurable. It's as though when you are hidden, working away under the car you are shielded from the outside world. Quite therapeutic.

Well... until it all goes tits up that is, then the swearing starts! :-D

Malcolm
M Le Chevalier

"Right, targets for my weekend:

1) change oil
2) check pressure relief valve is working -- "

It suggest that you reverse that order.

And in any event, since you've confirmed that the oil hasn't done any amount of real work, there won't be anything wrong with it, with regards to your oil pressure.
Lawrence Slater

Update: oil changed and when started from cold I got a whopping 40psi and no engine knocks. A victory dance was had. I let the car warm up then it dropped to 20psi and then 15psi. My victory dance was cancelled. The old engine oil that came out was ludicrously thin - more like onion soup than engine oil! No mayonnaise and no metal particles which was a small relief.

Now, onto the relief valve. Is it straight forward? If I release the tension am I going to get a spring firing at my chest?
Jamie Watt

Ps Lawrence - should've checked on here before I started, sorry!
Jamie Watt

Jamie

15 psi at idel is not bad, a general rule of thumb is at normal temp, 10psi per 1000 rpm, so your in the margin

Did your oil smell like gasoline ???

Looking forward to the news of the opv

Good luck

Yeah... im guessing you will get pissed on

Just wrap an old rag around the joint your loosening

Prop
Prop and the Blackhole Midget

Hey Prop,

Maybe I'm not looking too bad on the oil pressure side of things then., it's just the knocking I've got to eliminate now. I'm thinking about getting one of those automotive stethoscope gadgets to try to locate the noise. Every time I hear it I think it's coming from a different part of the engine!

And yup, the oil stank of gasoline, forgot to mention it earlier. Still no fumes coming through the rocker cover and I'm not seeing any oil coming out the exhaust.
J
Jamie Watt

Jamie,
If you have petrol in the oil you'll need to find out how it got there or the new oil will be ruined quick time. Could be a faulty petrol pump.

Best of...
MGmike
M McAndrew

And had you left the choke out whilst it was in storage?
Guy Weller

Yeah... it sounds like the petro thinned out the oil pretty badly

Id refill the engine with ""cheap 20/50 oil"" and a cheap oil filter and try run the engine agian... if your oil pressure improves and knocking reduced... then put a gold star in the win column, you got no issues with bearings and what not... maybe the OPV??? But that would just be a case of it sticking, due to poor oil quality, no biggie to fix id think...agian cheap oil till the fuel situation is resloved

Im just going to guess, pure guess... the carb mix is a little rich and the rings are not bedded in yet (500 miles) and the fuel is leaking past the rings and into the sump, besides you did mention you still have some blow by as you could feel air pushing back out the oil hole in the valve cover, so depending on the milage of this new engine ... it may just need some rough spirited harse driving for a few hundered miles to bed in the rings and seal up the bores then just a carb adjustment and then another oil.and filter change with a decent oil and your issues maybe solved... toss another bone to nigel for his theroy of fixing broken midgets is to simple drive them.

The next big issue is figuring out why how the fuel is getting into the oil...it could be leaking thur the carbs, maybe the fuel pump is acting up... im not sure if thats possiable but it does bolt to the side of the engine and has a v lever that sticks inside a hole in the engine block ...soooo, or it could just be grimlins pissing in side your engine.


But... id think your on a good road to beating this .... nothing I can see to loose sleep over.

But then agian, im good about screwing stuff up royally

Prop
Prop and the Blackhole Midget

Oh btw... you can do the same with a long screw driver with the handle placed agianst your forhead and not touching the steel portion of the screw driver with your hands,... just place the tip of the screw driver agajnst the part of the engine ...you will fill.the resonace inside your skull... just make sure no one has a smartphone on them when you do this...

But id guess its the lack.of good oil in the bearing shells, but id doulbt any damage at this stage...or an exhaust leak makes the same noise. Give the header nuts an.extra torque and see if that does anything...fairly common esp if the header/ pipe isnt strapped down and can move around, even slightly

Prop
Prop and the Blackhole Midget

Guy,

I note your comment on SU syphoning but Jamie said:
"I'm running a single side draft weber carb with the choke disconnected"

Anyone know more than me about these carb's? Is it possible to drain the carb in to the manifold (before the petrol evaporates) when not in use?

Best of....
MGmike
M McAndrew

Yes Mike, my comment was specific to SU carbs a while before Jamie mentioned his Weber.

Fuel in the oil can also accumulate over a period of time if the mixture is excessively rich. And if the car is poor at firing up and has to be cranked over for too long each time the car is started up. And if used for short journeys so the oil never gets hot enough. All contribute together to add to fuel in the sump.
Guy Weller

Contrat's on the first part Jamie. :).

It now seems far less likely that the pressure relief valve is the culprit, but it's still worth checking, since it's hard to imagine that much petrol dumping into the sump without you noticing the smell.

However, since the oil was indeed that thin, and if the engine was filled with the correct oil 2 years ago, and it's hardly been used, there clearly has to be something thinning it down. The most likely thing is petrol, and it most likely happens only when you run the engine, since over 2 years the petrol would have evaporated off I'd have thought. Or once thinned, does oil remain "damaged" by the petrol?

So either the top of the pistons are being flooded with petrol, or as Mike says it's leaking into the sump from the rear of the mechanical pump.

-- unless you got a petrol feed plumbed into the oil somewhere ;).


Lawrence Slater

Hey guys,

The mechanical pump is removed and blanked off and I have an electric pump instead. The weber does run extremely rich and I reckon I'll have to get them re-jetted at some point to calm the mixture down. Given all this hassle maybe I should be doing it sooner rather than later. I'll also check the cut-off valve is working in the float chamber.

Prop - I'm going to have to wait until the dead of night before I try the screwdriver/forehead trick. Can't be having the neighbours seeing me do that!

Thanks for all the help, folks!
Jamie
Jamie Watt

Just how rich are you running?

I've driven cars for months with the choke out, and not had the oil pressure drop that fast. Yours dropped in minutes, which suggests that the petrol must be flooding in.

Sounds like more than a jet problem to me.

So electric pump, not mechanical?

Which one?

Is the pressure too high, overcoming the float valve and squirting juice straight into the engine, injector style?


Any more suprises? Any other mod's so far not mentioned?
Lawrence Slater

>>The old engine oil that came out was ludicrously thin - more like onion soup than engine oil!<<

so it was worth dropping the oil out at least

Jamie,
beware of here, some owners are so tight-fisted they don't want to spend anything to diagnosis problems and get totally fixated on the immediate problem before them they neglect to consider that other faults that could influence the initial fault or that there could be more than one fault whether interacting with each other or not

an engine that sits unused for two years could have a fault that builds because of the time passed and lack of use

better to have good quality clean and fresh oil and coolant in your engine when you have a problem to give the widest margins of use
Nigel Atkins

Nigel. Tight fisted or not, checking the pressure relief valve in advance of checking the oil, esp' as the poster reported that it had done little to no mileage, was a logical step.

Also checking other things first would have been logical too.

As it is now, Jamie has lost around 10ltrs of good oil, and if using premium oil, that's circa 35 quid.

I agree, use decent oil, but only when you're sure you aren't going to drain it straight out again and throw it away, because there is an undetected underlying fault.
Lawrence Slater

Im stuck between lawerance and nigel, and its not stereo hi fi quality....haha

I think checking the OPV is a given and must be looked at, and knowing the oil is thin, it must be replaced no matter how expensive...but id only use the bargin basment discount 20/50 until the issues are sorted then use the good stuff

Lawerance makes an excellant point about the pressure of the fuel pump... for an SU HS4 duel carb, it needs to be between 1psi and 3psi but ive heard some have gone as high as 5 psi before needing a regulator

But you have a weber... id contact pierce engineering, for there input.

A side note... I think the knocking goes away with fresh oil, so I wouldnt be to concerned about tracing its location unles it continues after the new oil.

Last note... lawerance made a good point, what else do we not know about your new engine ? Contrary to popular belife, Mr. Guy is not some space alien weirdo that can read minds. Haha, so a little upfront info on mods is always appericated

Prop and the Blackhole Midget

how's he lost 10 litres of good oil? - the oil that came out was like thin onion soup, that don't sound good to me

the oil had been in a sitting engine for 2 years and as has now been shown picked up whatever contaminates and was not in good condition

refilling could have been held off until the reason for the state of the existing oil was found

and for your information even on two completely dry fills the most he'd have got in was 9 litres - Driver's Handbooks give this type of information for those not too tight to purchase them

if you'd have owned or read the Driver's Handbook for your 1973 Midget you'd have known it had a (nominal) 7 gallon tank and not 6 as you thought - I'm sorry I missed out commenting on that at the time but am very pleased to have got it in now

it must be torment to you to let your breaths out :)
Nigel Atkins

Aha.

The prize clown and all time joke, that great buffoon idiot known as Nigel, aka Nigella, is back in town. lol.

If you had even the wit of a dim-wit, you'd understand the many things that I won't bother to explain to you, as they are completely beyond the comprehension of your obviously feeble mind.

Night night Nigella. :).
Lawrence Slater

Aha

you're back to your puerile responses showing your true colours and the bravery of distance

and good morning to you Catweasle
Nigel Atkins

Your very welcome to come to TW and meet me. I'll say the same to your face. What will you do in response then? Beat me up. lol.

Lawrence Slater

Behave children! Not the time or place!
M Le Chevalier

Jamie, BTW, interested in your Weber setup. A have one too and kind of just guessed some settings. Don't think I am a million miles off but some reference would be good. :-)

Malc.
M Le Chevalier

Please Sir. He started it. lol.
Lawrence Slater

should we start them their own private thread so that they can have a go at each other.
mark 1500 on the road Preston Lancs

Hmmm

37 cent bullets at 49 Paces

Whaaa whooo whaoooohhhh


You er not wild bill hickock, and im not Doc holiday, and this aint dodge city kansas , I never said I couldnt shoot, I said I perfered not to.

Mr. Quiggly
Prop and the Blackhole Midget

Cheesy peeps!

A few questions for me to answer here:

List of mods/rebuilds:

New main bearings
New big end bearings
New little end bearings
New gudgeon pins and circlips
Cylinder number 4 relined due to previous circlip breaking and allowing the gudgeon pin to score the old lining
New piston rings
New head gasket
Skimmed head (to correct previous blown gasket damage)
Hardened valve seals
Kent fast road cam shaft
New timing chain (dual chains)
New clutch plate and cover
Peco tubular manifold and exhaust system (blowing at the 2-1 connection)
Triumph Tune crossover inlet manifold
Weber 40DCOE32 single carb. No idea what jetting it's running but I know it's over-fueling. Might not ever be a 40 32 as it was bought off fleebay
Standard distributor with electric points
Mega jolt coil
Mechanical timing has been done
Electric timing needs a bit of work
Thinking about getting a new jetting kit for the carbs

Typing all that has reminded me of all the money I've spent!!

Oh her than removing and giving the OPV a good clean I haven't had time to look into things this weekend due to hangovers but I'll replace the oil again to make sure I've gotten rid of the onion soup and see how things look.

Malc - I wouldn't look to my carb for setup advice as it's behaving poorly just now. I'll look into the jetting options and drop you an email with my findings.

Cheers,

Jamie
Jamie Watt

Also, facet fuel pump in the boot with in line filter and no pressure regulator. Part #40106 operating pressure 4-7psi at 32 US gallons per hour.
Jamie Watt

So, Facit pump. Don't they tick constantly?

Is it easy to drop the sump on a 1500?

Drop it, turn on the ignition, and see if fuel is pumped into the sump. Save yourself some more oil.

Or maybe pull a plug and look into combustion chamber for liquid petrol sloshing around.

You might also be interested in this picture. Read the note on the float levels, and the fuel pressure.


Lawrence Slater

The Facet fitted to my 1500 had to be fitted below the tank, so in the boot is not the correct place. On the rear bulkhead behind the seats under the car works for me.

Could fuel possibly be syphoned from the tank into the carbs and engine even when the engine is off, diluting the oil and causing your problem?
JB Anderson

Hi JB,

Have you got a picture showing your pump location? Surely it's impossible to get the pump below the tank unless you're fitting it to the bottom of the diff?!

Also been thinking, could the knocking be pre-ignition if the timing isn't set up correctly?

Lawrence - thanks for the info. Looks like i've got an older model with the brass floats. Im fairly sure it's a 40DCOE but not sure if it's a 32 or not. Trying to get a jetting kit from a UK supplier is also proving a bit tricky.

J
Jamie Watt

RE: Webers

Interesting you are running a 40 Jamie. So am I, but "most people" will say you need a 45 or dual 40s. At the risk of digressing, which manifold and what did you do with your dissy?

I dug out jetting spreadsheet last night. I basically just guessed some values based on what the internet said. It runs OK, although I haven't had it above 5 mph/2500 rpm, it is not tuned in properly yet and the plugs indicate I am a little rich.

So what I am saying is... who knows if I am right or not?! :-D

Malc.
M Le Chevalier

edit: I see you mention the manifold on you previous thread. Cross over type. Same as mine again.

The one thing I am missing (and it's a bit of a big-un really) is a decent exhaust.
M Le Chevalier

Hi Malcolm,

When i was doing my (albeit limited) research most people were recommending the single 40s as twin 40s or a single 45 were deemed to be too much. Who knows, though!

I've gone for the peco exhaust system you get through Moss Europe and i have to say it makes a fantastic burble. Coupled with the intake noise from the weber and you've got quite a nice orchestra around your ears!

Are you able to send through the jetting spreadsheet?

Re distributors, there isn't a place to connect the vacuum advance on the weber so i've blanked it off just now. I'll probably change dizzys at some point in the near future just to make everything a little less heath robinson. I got a local garage to tap a power take off from the manifold for the brake servo and it works well.
J
Jamie Watt

I haven't got a weber to check. When they flood, do they flood internally or externally?

Your Facit pumps at 4-7psi, you said earlier.

You don't think that this is significant then?




Lawrence Slater

Jamie, I would say my Facet pump is level with the tank centreline depth wise, but is certainly not above the tank as it would be if inside the boot.

Preignition or pinking would not occur unless the engine was under load, so at tick over this is unlikely to be your problem.

It does sound to me that your oil has not been working as oil due to contamination , by fuel it would seem, and therefore knocking bearings is quite a likely outcome. That is assuming the relief valve is seating properly.

Knocking is different to tapping which is mostly heard due to faults at the rocker shaft lubrication which is poor on the 1500 engine. A knock is most likely due to main or big end lack of lubrication .
JB Anderson

I agree with Lawrence. I think a fuel regulator is a good idea. I have a 'facet' type cube pump and regulate that to suit my twin SU carbs with a Filter King adjustable regulator. Because I've not yet run the car on the road under full load, I've not set the final pressure but thus far it's as high as possible without overcoming the float-bowl needle valves and that will most likely be the optimum setting. I don't know how prone your particular Weber is to over-pressure but most require between 1.5 psi and 3.0 psi. Your facet pump will probably run at double what's required.
Nick Nakorn

This thread was discussed between 21/10/2014 and 29/10/2014

MG Midget and Sprite Technical index

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