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MG Midget and Sprite Technical - Intermitent 'Ticking' Noise

Hi everyone, hope everyone is well and enjoying the sunshine :-)

I know "it sounds like..." problems are a bit hard to diagnose via the interweb, but I am looking for suggestions on a weird quirk that my 1500 has been exhibiting for as long as I can remember.

The noise is a clicky/ticky noise that tends to be loudest at light throttle at approx. 3500rpm (so particularly noticeable when cruising around 50 mph).

If I ease off or speed up the sound will go away. I can "control" whether it makes the noise or not with the throttle.

If I drive it hard for a bit (full throttle, lots of revs etc.) then go back to cruising the noise isn't there initially, but slowly comes back over the course of a minute or two. Quietly at first, then builds until quite noticeable again.

Suggestions welcome. Unless you are thinking imminent engine explosion! :-)

Malcolm.
Malcolm Le Chevalier

Malcolm,
if you record the sound some are so good they might be able to identify the noise - I remember at an event an engine builder correctly identified a problem over the phone within about a second.

Is the noise heat/cold related too?

Guesses - fuel system, timing, ignition, cooling (oil and/or water), yes I used to make chocolate fireguards.
Nigel Atkins

Just a stab in the dark Malc - do you have a butterfly loose on the spindle?

"If I ease off or speed up the sound will go away. I can "control" whether it makes the noise or not with the throttle".
Greybeard

Was the PO a taxi driver? Maybe it's the meter still ticking?
GuyW

Malcolm,

When you built that engine, how much piston to cylinder clearance did you build in. I think I remember that piston slap is most noticed at very light throttle. Someone correct me if I'm wrong.

Charley
C R Huff

Might be worth running it with the fan belt removed. Just briefly as a test. It would eliminate e.g. the alternator but also cuts out a lot of other noise and may make it easier to tell where the ticking is coming from.
GuyW

Along with guys suggestion if you can replicate while sitting still get a ajtomotive stethescope from machine mart (cheap) or a long screw driver with the handle held onto your forhead (yeah its wierd) and just press around and listen for the location

Something like that could be 287 differsnt things..frrom a loose screw in rhe timing cover to a worn anti rattle spring in the gear shift handle

Prop
1 Paper

Another stab in the dark; It's not the speedo cable? I had a Fiesta make a ticking noise once, but only at a certain speed and altering the throttle setting caused the engine to move enough on its mounts to stop the noise!

Jim
J Smith

Thanks everyone. I think Charley might be on to something.

I have checked out some videos on piston slap. It's a similar sound to what I have.

It would explain my low compression on no.3 if it was on that cylinder. (The low comp. was not cured by head rebuild, so must be a lower engine issue).

It would explain the marks I have/had on the front and back walls of the cylinder when I last took the head off.

It would perhaps explain why the sound goes away if I rag it a bit. Higher revs means more temperature and lubrication so the noise disappears. Go back to cruise, the piston cools a little and the sound returns.

I didn't pay attention to clearances etc. when I rebuild the engine years ago. It was already bored to the max. size (+40) so there wasn't much I could do with it anyway. Just rebuilt with new rings and crossed my fingers! :-) Damn!

Probably time to browse eBay for a short engine. Gearbox needs to come out too anyway!

Malc.

Malcolm Le Chevalier

Malc,

I thought the same as you about the elevated temps when working it, but didn't bother to mention it.

I didn't realize that you hadn't bored it at the time you built it. Not doing so would increase the odds of piston slap being the issue. If you had thought to measure it at the time, you might have considered having the pistons expanded to fit tighter (if any shops still do that today). Expanding pistons is also known as knurling. They run a knurling tool across the piston skirts, and the raised metal gives a tighter fit.

Get some other opinions, but I am under the impression that you can live with piston slap for a long time. Might be worth trying some Lucas Oil Stabilizer or STP to see if that quiets it any.

I'm a little surprised that the 1500 can't be punched out more than 0.040 inch.

Charley
C R Huff

Malc, should've said last week. I know where there's a standard block for refurb ;-)
It's not mine so would need to be exchanged for beer tokens, just not sure how many....

Best of....
MGmike
M McAndrew

Yeah, think I will just have to live with the clatter for now, whilst I ponder what to replace it with. 6 cylinder maybe.... :-)

Malc.
Malcolm Le Chevalier

I know you'll have checked this but.... advance on part throttle?
And you can go +.060

Best of...
MGmike
M McAndrew

Light or feathered throttle when running at medium or slightly above revs gives a weak mixture. If you are using the standard carbs on a 1500, they were set up for economy, and are liable to run on the weak side. Coupled with Mike's question about advance - sure it's not pinking? How do the plugs look?
GuyW

When the big ends went on my 200SX it displayed this exact symptom. Hopefully it's not that, but it would also ring true with what Charley is saying.
Karl Bielby

Fueling is on the rich side of 14.7:1 AFR. Advance should be OK. I am running factory spec on the mechanical and not using an overly ambitious vac. advance. So I don't think its pinging.

In theory you can go +60 on a 1500, but everywhere I look the pistons are out of stock or on back order, which is code for don't exist!

I would hope not big ends as the bearings are < 10k miles old! But I suppose I do rag it :-D

I am tempted to build a 1300 to drop in. A bit more revvy, less prone to blowing itself up and I can re-use all my go faster bits from this engine.

Cheers,
Malc.
Malcolm Le Chevalier

Out of Interest.. does the gearbox fit a 1300? I have wondered about doing the same for when my 1500 needs rebuilding.
Karl Bielby

Should do! :-)
Malcolm Le Chevalier

I dont think a triump gear box fits a 1275 unless you mean a 1300 triumph

If thats the case... and considering a rebuild id re think this and do a inline eco tec or a ford durotec

If had mine to redo agian ... id have gone to the salvage yard and got a suzuki swift 1.3 l with a sameri 5 speed ... yanked the efi and ignition system off and stuck 4 SU HS1 CARBS on each cly and did a ford edis crank trigger ignition system and done

Sure you lose a few hp butthat engine cranks out 250hp so even loosing 100hp your still left with 150hp, from the factory mg are 60hp ?

A modern day engine with 5 mains last 250,000 miles alot of extra hp more reliable...and a heck of alot many Xs cheaper then rebuilding the orginal stuff

Bugsuki got that engine and 5 SPEED for $500 but he kept the efi and factort ignition system and paid huge $$#$ for that luxuary

I think GM metro is almost the same engine as the suzuki swift engine ...???
1 Paper

Worn small end? I had just that ticking at 3-4000rpm (998 A-series though).
L B Rose

This thread was discussed between 24/05/2017 and 08/06/2017

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