Strange engine noise = engine rebuild!!

Post by **DAVIDMCCULLOUGH** » Mon Apr 20, 2009 11:25 pm

So last week i fiited my new carb and the MM was running great. I uesd it for work a couple of days, no problem. I took it for nightshift on Friday night, washed, started polishing between calls and was happy!

Then on Saturday morning I started it up to go home and within 300yards a strange noise developed. I pulled in as I thought it had maybe snapped a fan belt and it was hitting off something. Nothing obvious. Started off again and within 1/2 mile the noise got much worse and and basically sounded like a bag of spanners. Oil pressure maintained at 60psi the whole time. At this point I decided to call the AA and get taken home rather than risk doing any further damage. Great service from them, they arrived within 25 minutes from me calling and the guy didnt question when I said I would like it recovered home (Dont think he had saw a sidevalve engine before though!!)

So any ideas what this could be? Think it may be a bearing but Im looking for other suggestions before I start removing the sump.

Thanks in advance!
Dave

Post by **MarkyB** » Tue Apr 21, 2009 9:26 am

Can you be more descriptive about the noise?
Does it still make it when ticking over?
How fast is it in relation to the engine speed and would you call it a tapping or a knocking noise?

Post by **DAVIDMCCULLOUGH** » Tue Apr 21, 2009 9:39 am

It still has the noise when ticking over and gets louder as the engine gets warmer or as you rev it. No loss of power and good oil pressure.

Its hard to describe the noise, its not like worn mains on the A series as that noise usually goes away after the oil pressure is up so I suppose its more of a very loud tapping that sounds like metal on metal.

Post by **mike.perry** » Tue Apr 21, 2009 9:28 pm

Try turning the engine over on the starting handle and feel if it turns over without catching on anything. Check that the fan blades aren't touching the radiator or anything.
Check that the air filter is tight on the carb. It can rattle if it comes loose. I assume that as it makes the noise when stationary then it is not the gearbox. Check the clutch is ok.

Post by **MikeNash** » Tue Apr 21, 2009 10:21 pm

David,
If the noise is in time with the rotation of the engine and gets worse with more throttle, try checking the tightness of the mainfold nuts. You may have an exhaust leak under pressure which sounds rather like a bigend.
Of course, I only found out AFTER I'd pulled the sump and checked the bigends, etc......
MikeN.

Post by **alanworland** » Tue Apr 21, 2009 11:17 pm

I can remember sometimes after a good fast run the next time I started the engine a valve would stick open - not sure if inlet or exhaust but this would make an alarming tapping type sound until after a while (half min) the valve would close and operate normally, I think lubrication up inside the valve chest wasnt as good as it should be and the valve had stuck/siezed in its guide?
Check for 4 compressions
Put a very long screwdriver at points around the running engine (VERY CAREFULLY!) with the handle to your ear, you might be able to locate it better

Post by **DAVIDMCCULLOUGH** » Wed Apr 22, 2009 12:27 am

This afternoon I went down to Dads to were the MM was recoverd to by the AA. Dad had moved it and the noise now sounded terminal.....

So off with the sump, no signs of any metal filing and not much gunge in the sump. We took off each cap in turn and they are all perfect! Bottom end ruled ot.

Cylinder head next, straight away the cause was obvious. The piston ring on No4 cylinder had broken up and destroyed the top of the piston. I removed this one and tried to clean up the top but it was too bad. Cleaned No1 and its been bored +10 already, one of its rings was also starting to break up. The bores are a bit worn and the groves in the piston are really loose. Dad thinks thats why the rings broke up because they were hitting the wear ridge. Apparently modern rings have a stepped edge to allow for this? Do you think better performance from the new carb would have made this happen or just coincidence that it happened 30miles ater fitting it?

So it will require a rebore and new pistons, but at least they are readily available! I am much happier now that I know whats going on. So tomorrow Im planning to take the block out of the car as I did all this with it still fitted. Shouldnt be off the road to long....

Post by **mike.perry** » Wed Apr 22, 2009 10:12 am

Glad you have found the problem. Make sure you have the pistons/rings before you get the rebore, just in case the size you want is not available.
The new carb had nothing to do with the engine problems, the s/v can take an awful lot of abuse, Alta conversion, supercharger, 60mph motorway cruising etc., just co-incidence.
Normally if something breaks up in the cylinder it gets chucked out of the exhaust valve, hopefully without doing too much damage.
Take care fitting the sump gaskets and oil seals

Post by **MarkyB** » Wed Apr 22, 2009 7:04 pm

I was about to suggest a head gasket problem. This can sound terrible when it's gone between the two middle pots.
I'm afraid

better performance from the new carb

may have been a contributory factor.
If the wear ridge has been established by someone pottering around for years then "pushing the envelope" a bit will lead to this kind of damage

.

Post by **alanworland** » Wed Apr 22, 2009 9:40 pm

Not long after getting my Morris with about 50,000 on the clock of 'reserved' driving it was thrust up to an indicated 80 (yes 80!) MPH down a slight incline and all cylinders lost their top rings!
I am of the opinion that a bit of a carefull thrash now and again is almost good for the engine? - at least it keeps the wear ridge a bit higher up the bore!

Post by **DAVIDMCCULLOUGH** » Wed Apr 22, 2009 11:54 pm

I have checked with ESM, they have +20 +30 +40 thou in stock. The first question I was asked when I phoned the reborers was, are you sure you can get pistons!

Today I was trying to remove all the studs, but the 4 beside the manaifold and one at the middle front are stuck solid. I was using a really old tool called a footprint which was great but its probably as old as the car and it broke. No luck with locking nuts together, vice grips or penetrating oil so far. I have ordered a stud extractor made by draper from my local motor factors, but it wont be in until next week. Any ideas?

Post by **DAVIDMCCULLOUGH** » Wed Apr 22, 2009 11:56 pm

Nearly forgot, this is a pic of said piston.<br>

<br>

Post by **mike.perry** » Thu Apr 23, 2009 10:01 am

One for the trophy cabinet.

Maybe the machine shop doing the rebore would be better equiped to remove the studs.
Remember the threads are metric.

Post by **Kevin** » Thu Apr 23, 2009 11:08 am

DAVIDMCCULLOUGH wrote: Apparently modern rings have a stepped edge to allow for this? ...

Hi David the stepped rings were made by companies like Cords and they were for using when overhauling an engine that didnt need a rebore but had a small wear ridge which the step would avoid.
There is no need for new rings to be stepped with new pistons and a re-bore, I cannot imagine what the benifit would be.

Also remember that proper penetrating oil can take a day or two to do its work the problem is often down to people using WD40 which is not a penetrating oil like Plus Gas, but anyway the workshop will be able to get them out for you.

Post by **stevey** » Thu Apr 23, 2009 1:32 pm

One for the trophy cabinet

give it a polish and put it in your china cabinet. How bad was the bore after that? Are you taking it to OD cars to get teh rebore done?

Post by **DAVIDMCCULLOUGH** » Thu Apr 23, 2009 11:38 pm

Yes OD cars have quoted £80 + vat for the rebore, not sure what it will cost to get the spare head skimmed but wont be much in the grand scheme of things!
The dynamo bracket on the original head is cracked and I managed to pick up another at last years national for the bargain price of £10.

Post by **DAVIDMCCULLOUGH** » Fri Apr 24, 2009 11:36 pm

All studs now removed with the benefit of a stud extractor. The 4 beside the manifold where really difficult to remove, the bottom of the threads were in really poor order and appear to be down into the water ways.. Is this corrcet for a sidevalve as it seems very strange. New studs will be needed!

Post by **Kevin** » Sat Apr 25, 2009 7:56 am

Hi David I dont know about the sidevalve engines but its got to be worth getinr hold on the correct tap to clean up those threads to make them nice and clean and free from dirt/grit etc as it sounds like they were possibly overtightened and certainly need a clean up.

Post by **mike.perry** » Sat Apr 25, 2009 8:30 am

It is quite normal for the studs to be rusty at the bottom and the studs on the manifold side are subject to the heat of the exhaust system which is why they can be awkward to remove. Well done for getting them out without snapping them.
If you have to cut new studs I think the thread is Mx10. I can't remember if they are the same pitch both ends I will check later this morning.
My job for the day is changing the MM radiator. My radiator is leaking around the bottom hose. All the radiator repair firms around Reading seem to have disappeared.

Post by **Kevin** » Sat Apr 25, 2009 9:47 am

Hi Mike are these people any good

http://www.berkshireradiators.co.uk