1935 Augusta Cabrio - Engine siezed on M4 without warning

[mariof]

Hello fellow Augustists,

To anyone in the middle of rebuilding an engine, or thinking about it, here is a cautionary tale of an exhaust valve on No 4 cylinder breaking and embedding itself in the top of the piston, locking the engine and bending the con rod. So you might want to consider replacing those old valves while you are at it.

I was driving on the inside lane of M4 at a steady 55mph a couple of days ago...all systems normal, engine running cool, oil pressure normal etc when the sound of something breaking...not quite a bang but more than a tinkle and suddenly engine stops and I coast on free wheel onto the hard shoulder. First thought was cam chain or tensioner failed. Four hours later the rescue truck arrived and we loaded the car onto transporter.

Took the head off today and this is what I found - the pics speak for themselves - the exhaust valve hadn't dropped, but decided it had enough of bobbing up an down for 91 years and thought, what the hell, time to say hello to my old friend Piston and detached it head from its stem and went on a suicide pact taking old faithful Rod Con with them.

[mariof]

Number 4 exhaust valve, piston and con-rod

[simonandjuliet]

Ouch ! What a shame. Hopefully the head and block are not too badly damaged

Good luck

[lancialulu]

Exhaust valves seem to corrode around the lower part of the stem as exhaust gases are acidic. If an engine has had periods of non use this corrosion accelerates due to moisture from condensation.

I have seen this on Fulvia engines.

[mariof]

Head and Bore seem OK...very little damage...I hope the crank is OK...will find that out when I take apart, but hopefully the conrod bending softened the blow a little.

Does anyone out there know of any new (modern) replacement valves that fit? I do have spare Augusta, but am thinking modern materials might be safer.

Mario

[Kari]

I am sorry to see this. I had a conrod bearing failure on my Augusta last October, 500 miles from home.

Cavalitto has new valves for the Augusta.

IMHO, by the look at the cylinder head picture, it seems as that cylinder has been running at a high temperature. Compare with the others.

While the cylinder head is off, I suggest to check continuity of the water channels around No 4 cylinder head. Most important is the blue connection.

Karl

[mariof]

Hello Karl,

We met at LMC National rally a couple of years ago. Thanks for the info regarding waterways...I will check it out tomorrow...there is quite a bit of flaky rust in the block and head...do you know of any way to dissolve it without damaging what's left? 

Am going to Turin next week and will be calling at Cavalito's....new valves are on my shopping list. I need to measure the bores for a replacement piston as it has been rebored some time in the past...do you know the range of oversized pistons that might be available?

Best wishes

Mario

[Kari]

Hello Mario,
I am sorry, my memory of names is bad.
To remove rust particles I'd use a length of wire and a vacuum cleaner which has a small flexible plastic hose attached to the hose. I am not sure if a chemical treatment would be safe.
The walls of the intake manifold are only of 3 mm thickness.

I think, the chance to find a sole replacement piston and rings for a particular diameter and important, the same (within +/- 5 gr.) mass (weight) is remote. Probably, you'll need to bore the cylinders
slightly to a new diameter and replace all pistons. This way you'll have a good top overhaul with the new valves.

To my knowledge, there aren’t any oversize pistons on the market. Lancia offered 5 oversize pistons of 0.20 mm steps up to 70.85 mm bore.  British Augusta owners have been using Triumph Herald pistons in the past.

I might be of help with a conrod but I'll need photos and dimensions of the bent one. Best by PM.

Cheers

Karl