Sick Engine

[Henry Harris]

I have an engine that requires a bit of remedial work......

Number 1 valve spring, exhaust, is broken into 3 pieces. 

The exhaust valves and fittings are standard Austin but the springs are 46.5mm long (free), possibly Austin Maxi?

   

I have never seen a broken valve spring on an Austin engine before now.

These pistons are fitted. Honda? Real or fake?

   

   

   

   

[Ruairidh Dunford]

Standard spring - January 2020:

   

   

[Stuart Giles]

Just checked some new Terry's Standard Maxi springs that I have here. They measure 46mm free length, so that's quite likely that's what you have there.

Edit: Here's a standard Maxi spring and an "A" series valve and re-machined cap along with an A7 setup for comparison from a motor I built a while ago.


 
I have used Terry's "performance" Maxi springs in a race motor, these are actually shorter (at about 42mm) than the standard Maxi spring but are a fair bit stiffer, a race motor would pull 7500 in top gear with these fitted.

[Henry Harris]

What would cause a valve spring to break?

[Bob Culver]

Subjetc to acid at some stage?

[Charles P]

What would cause a valve spring to break?

Material fault
Harmonics
Coil bound
Three amongst a range of options

C

["Slack Alice" Simon]

Sourced in China, where they sometimes do not know how to temper metal.

[Ruairidh Dunford]

What would cause a valve spring to break?

Cause might be:

- not seated correctly
- coil bound
- incorrectly treated during manufacture
- flaw in/inferior material
- foreign material trapped in spring

I do not know the source of the spring in my photo.

[Stuart Giles]

What would cause a valve spring to break?

Material fault
Harmonics
Coil bound
Three amongst a range of options

C

Wouldn't have thought coil binding would have been Henry's problem unless the cam had really radical lift as the Maxi springs have fewer (but thicker wire) coils than the A7 ones. But as apparently Henry's motor was using the A7 valves rather than the longer "A" series ones more commonly used with this setup, the seat pressure and therefore spring preload would be quite high.

Sourced in China, where they sometimes do not know how to temper metal.

Possible that the Seven Workshop etc. A7 springs are amongst the tons of car parts that are Chinese manufactured even when apparently UK sourced. Wouldn't have thought it likely that any of those dusty old boxes of Terry's, Tranco etc. Maxi valve springs that have been and are being used in A7 motors would have been manufactured offshore.

I have experienced apparently random valve spring breakage, but not so far on an A7 motor. Exhibit A m'lud...



Couldn't see any reason for this breakage, but I hadn't built the motor, so it's possible the builder had  re-used the old springs. Fitted new ones checked for binding etc. still running OK 5 years later.

[Hedd_Jones]

Henry

When father rebuilt the engine for the RP here in the mid 1980's, he put a full set of new springs in it. An otherwise standard engine (HC head excepted). These springs come from Mick Kirkland, not that it matters.

It was 1990 by the time the rest of the car was ready to go, despite a rebore, the block was porus and an early breakdown was the result so the the block got sleeved etc and it was 1991 by the time the car got serious use.

Going to the 1991 Anglesey rally, my mother driving alone (father and I were already in Anglesey with dads Autojumble stall) and she suffered a serious missfire about 2/3 way there. She had the problem that we were closer in Anglesey than home was, no AA or RAC membership, and no mobile phones back then. Somehow she got a message to the hotel in which the grounds of the event was being held (via a payphone), which was basically car playing up, going to be late, if I am very late assume its broken and come looking. We got this about 5pm by this time dad was getting a bit worried having expected her mid afternoon.

So we went hunting her in the van, we got to the Ogwen Valley, and dad parked next to the lake, I believe to get his head together. Mum was supposed to be going via the A5, but there had been no sign of her and we had come a fair way, dad was second guessing himself, had she come via the coast? Anyway it was getting on for dark now (in early May). I scrambled up the scree opposite the lake (basically the base of Tryfan), got onto a bit of a flat bit quite high up. No soon as I got up there I could see these weedy lights in the distance, and sure enough it was mum in the Seven. She had seen dads van and parked up next to it by the time I had got down.

The car was running like a sack of shit, missfiring, no fiddling with the timing would cure it. The oil smelt of petrol, but otherwise was free of metal, and it was certainly not knocking anyway.

Mum didnt like driving the van and concluded the little Austin got her that far, so it would get her to Anglesey. So I got to ride with her for moral support and dad followed in the van.

Morning after dad took the head off, found nothing of note, he then took the valve chest cover and found a broken spring. He changed it for a spring he had in the Autojumble which seemed near enough, did an oil change and mum drove the car home running sweet as a nut.

2 months later on a day trip to Cerrig Y Drudion it did the same thing, we pulled into one of my school mates drive, dad took the valve cover off and found another broken spring. So he simply drove home with it missing.

I believe dad spoke to Mick about it, and seemingly there was a bad batch which Mick knew about and I believe offered dad another set FOC. By this time a set of used ones were in place and remain there to this day. The replacement set Mick supplied are in my Chummy.

The engine has since bust a crank and been 'rebuilt' again. There were no lasting problems.

I'd say you've got a bad batch, Change them all.