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MG MGB Technical - New MGB engine rattle

I've recently had my MGB engine reconditioned. Its back in the car and runs well. However, there is a rattling noise that sounds like tappets but isn't as they are adjusted correctly. It sounds more like a diesel engine rather than a petrol engine. Has anyone any ideas/experience of this, and is it likely to quieten down as the engine runs in?
J Reckitt

Tappets can be difficult to adjust correctly. In theory the base circle i.e. greater than 180 degrees round the back of the cam should all give the same clearance, but it isn't always.

In my experience on mine and several other cars the point of greatest gap isn't always at the 'rule of nine' point (if that is what you use) and can be varying as it passes through that point. That means not only is the maximum gap excessive, but it's also difficult to get consistent measurements with feeler gauges unless you position the engine in _exactly_ the same point every time.

I start with the 'rule of nine point', then turn back and fore for there looking to see if anywhere is larger, then adjust there.

Other than that there can be any number of reasons why a rebuilt engine is noisy. Exhaust/intake leaks?
paulh4

Paul beat me to it I was thinking perhaps manifold/gaskets leak.

I find, especially modern made fixings come loose with use/mileage, time, weather, heat cycles.

I recently had a small coolant leak and it was a jubilee clip that just needed nippy but when I done the work in summer I checked all clips, even those I hadn't touched, a couple of times and nipped up as required but I could nip them again in cold winter.
Nigel Atkins

J,
has your engine been fitted with an uprated camshaft?
When I got my car it was fitted with a rebuilt engine with a fast road tuned cylinder head and a stage 1 camshaft (a Piper BBP270 Fast Road cam I believe).

When I first drove it I commented on the loud tappet noise and I was told that it was probably down to the Fast Road cam.
Even though I adjusted the tappets on numerous occasions, I never did get them to run any quieter.

However, I ran that engine for around 10 years with noisy valve gear without any problem.

Most likely the rattle was due the to tolerances in the valve train being too large from the start.

I recently fitted a 5-bearing MGB engine to my car and it has surprised me by almost has no tappet noise at all.

Do you know any engine experts near you who could have a look at your engine for you?

Cheers
Colyn

( PS. I hope this isn't the case but a blown cylinder head gasket can sound like a loud metallic rattle bit you would normally notice the misfire and the drop in power if this was the case) Also a blowing exhaust gasket could be the problem as has been mentioned)
Colyn Firth

Buy a better Radio!
Pat Gregory

Thanks for your comments. I have got a tame engineer so I will go and see him. Its a bit difficult because he offered to re-build the engine but as he is known to take years to finish things I said no!
As regards the radio suggestion, its difficult to find a radio that works with a positive earth electrical system!
J Reckitt

They are around, as are inverters https://mgaguru.com/mgtech/electric/et207.htm
paulh4

JR
Something to think of with tappet clearance
Std. MGB cams run .015" Cold clearance and that seems to be ok----But
'If' you have an aftermarket reground cam the clearance is usually quoted as a running clearance, which means Hot
Opening a can of worms here but,-as I see it this doesn't really mean that you have to have the engine running to set them, just hot, with the valves right up to running temperature
It's hard to get good settings as the valves cool off quickly with the valves on their seats, so I cheat---my method for hot running clearance setting is--for example
Say the clearance is to be .016" hot
I get as much ready as possible with feeler gauges and spanners/screwdriver ready to go-
Run the engine to get it as hot as possible with a blast up the road if possible, then while it's nice and toasty,get the cover off and set one inlet valve and one exhaust to the quoted spec (.016") then leave it to get dead cold without moving/touching it-Don't touch it at all--leave overnight maybe
When it's nice and cold, remeasure the two set valve clearances without touching anything else or turning the crank at all
You should get something like-
Inlet--.014"
Exh--.017"
for a .016" hot setting cam
You can then use these new specs to set your clearances cold instead of burning yourself getting it done hot
willy
William Revit

In addition to all the wise words, there's also possible wear on the valve tip and tappet adjuster to be taken into account. A small dip occurs in the valve tip that the feeler gauge can't detect, so the tappet is adjusted on the wrong clearance. Old lags used to be able to set up valve clearances by ear to counteract this. There also used to be a proprietary SPQR tappet adjuster that took this into account.

Because one needs a stepped feeler gauge, that I haven't got, on my Triumph 650 I set up the valve clearances by no of turns on the adjuster eg a quarter turn equals, say, 5 thou. There's probably a formula for working this out with the UNF TPI on the MGB tappet adjuster.
Peter Allen

gunson's ClikAdjust now ... and why you don't need it https://mgaguru.com/mgtech/tools/ts080.htm :o)

Includes the formula for calculating how many turns of the adjuster screw are needed for 15 thou - 0.254. Mind you, it also says the adjuster thread is 5/16"-24, which is the same as the HS carb air-cleaner bolts ... can it really be that big?
paulh4

All good ,but this is supposed to be a reco engine.-Wouldn't the rockers have been checked and resurfaced and new bushes/shaft
I would expect these to have been done-

Diesel sound ,that's big, sounds nasty
Was the engine rebored-
If not and the ridge in the bore wasn't removed the new rings 'might' be tapping the ridge-not good
Or it might have the pistons in back to front
Depends on the old -whodunit- reputable-??
willy
William Revit

"I've recently had my MGB engine reconditioned".
What actually gets done on a re-build is entirely dependent on who is doing it. Should be itemised on the bill.
Rattles?
New timing chain and tensioner or old?
New cam and followers? Did you do a "bedding in" 20minutes?
Re-bore? If not, the top rings should have a chamfer to stop them impacting the wear ridge.
New or re-surfaced rocker? Ridged faces will make accurate feeler gauge setting impossible.
Allan Reeling

Thanks everyone for your comments. On the new engine re-build everything was replaced/reground/re-bored, except for the rocker assembly.

I am considering getting a replacement one. Do you think that's a good idea?

Also, there is an article in the MGOC magazine this month outlining how someone modified the oil delivery system on the rockers using a brake pipe with holes in to ensure everything gets oiled correctly. It seems a bit Heath Robinson to me, but he reckons it solved the problem. Has anyone come across this solution before, and does it work?
Jim
J Reckitt

Have you taken it back to the reconditioner to see what he says?

When people come up with Heath Robinson modifications such as you describe I despair, same with cooling, fuel 'problems' and others. How many millions of these engine have been built? How many decades and millions or hours have they run? How many had a problem that needed this cure? If it needs something like that then there is a fault that could be found and fixed properly. OK, it's a work-around, but what else might it be covering up is what I would ask.

Have you tried running the engine with the rocker cover off? There should be plenty of oil in evidence. If there isn't then maybe the head passages are blocked, in which case a different rocker assembly would make no difference. Or maybe one or more rockers is blocked. It would also allow you to put a listening-stick aka mechanics stethoscope on each looking for differences in sound. Do you have the matching rear rocker pedestal for the head? There are heads with in-line and offset feeds, the rear pedestal has to match. Removing the rocker assembly to inspect or replace requires slackening all the head nuts in the usual sequence, and probably a new head gasket.
paulh4

Something else here
Are you sure it's internal
Could it be something external like loose bolts in the waterpump pulley or for that matter maybe a crack in the drive belt, they can make some terrible noises
Also broken springs in the distributor cause an almighty racket
Suggestion--get a piece of garden hose or similar ,up to your ear with one end and go around with the other end and try and track down exactly where the noise is coming from
willy
William Revit

Just replace the rocker gear.
Chris at Octarine Services

IF it's the rocker gear
William Revit

Could failure to install the two 0.005" shims, on the two centre pedestals of the rocker shaft, cause a rattle, I wonder?
Allan Reeling

Jim, does your engine have an engine driven fan?

I recently fitted a new plastic fan onto a 5-bearing MGB engine and when we started the engine there was an awful clattering noise from the front end.

It sounded pretty serious and if we hadn't just fitted the new fan we would have thought that there was a serious mechanical problem in the engine.

All that was actually happening was that the back edge of the blades were fouling very slightly onto the crankshaft pulley but it really did sound as if something was broken!

A simple space solved it.

Colyn
Colyn Firth

Allan,
I rebuilt my rocker system and managed to leave my two shims in my spare parts pile. No noticeable rattle resulted.

Regards
Roger
R Taylor

The shims are there to stop the shaft fretting in the pedestals, so could conceivably be a source of noise if not present.

The engine-driven fan can hit the engine if you have the short-nosed pump and shallow pulley without the spacer. I discovered that when I noticed my fan was the wrong way round, and tried to correct it. My fan - for whatever reason - has the mounting boss offset wrt the blades as in the attached so does fit the other way round without fouling. Other fans I have seen seem to be more central. Things like this may account for the discrepancy in blade to radiator spacings that Roger Parker has reported.



paulh4

I had a valve train "clicking" that was uncharacteristic in mine. It turned out that the rocker shaft was not properly secured and was turning side to side and clicking against the hold down screw. I replaced the shaft and screw and things quieted down.
Glenn Mallory

Does it have the shims under the centre two pedestals? Not fitted originally but recommended (Haynes) for use on earlier engines, they seem to clamp the shaft by putting the holes in the pedestals very slightly out of line. The location screw has a tab that locates in a slot in the locking plate, so the screw will only fit in two position 180 degrees apart, and the chances of the tab lining up when the screw is holding the shaft tightly are pretty slim.
paulh4

This thread was discussed between 06/03/2019 and 22/04/2019

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