And then it went Bang

[Derek Sheldon]

Charles , no problem with my Rosengart engines They are all metric

[Dave Wortley]

You could use big end bolts from one of the cherished suppliers. They should be higher tensile strength than 8.8 grade.

[Alan]

The interesting thing is the broken studs. Studs don't just break, my guess is it's a fatigue failure. If the clamping load in the joint is less than the cyclical loading of the valve train or combustion pressures etc there will be fatigue implications. If one bolt goes, the rest will follow. The cause is loss of clamping load in the joint, either insufficient tightening (and I don't believe Charles would do that), or the bolts have worked loose somehow. Maybe vibration or relaxation of the gasket if fitted. 
That said, hydraulic lock is still a possibility. Quite often there's no residue of water or fuel because the engine was hot and by the time you get to it it's evaporated. The studs will tell. If it's a fatigue failure it's option one. If it's not, them it's either a piston stuck in the bore or it's hydrauliced.

[Charles P]

The interesting thing is the broken studs. Studs don't just break, my guess is it's a fatigue failure. If the clamping load in the joint is less than the cyclical loading of the valve train or combustion pressures etc there will be fatigue implications. If one bolt goes, the rest will follow. The cause is loss of clamping load in the joint, either insufficient tightening (and I don't believe Charles would do that), or the bolts have worked loose somehow. Maybe vibration or relaxation of the gasket if fitted. 
That said, hydraulic lock is still a possibility. Quite often there's no residue of water or fuel because the engine was hot and by the time you get to it it's evaporated. The studs will tell. If it's a fatigue failure it's option one. If it's not, them it's either a piston stuck in the bore or it's hydrauliced.

No gasket, just 515. All tightness checked just prior to the weekend.
My money is also on a stud letting go leading to a daisy chain of breaking studs, arrested only by the through bolting on the valve chest side.
After sitting for 3 hours parked up at Rolt corner no water had leaked back into the bores, suggesting to me that a hydraulic lock was probably not the root cause (yes, the rad was still full)
 
Charles

[Austin in the Shed]

Was your engine bolted down solid ?
I have been helping a friend with his magneto engine over the weekend albeit a high mileage standard unit,I couldn't believe how many cracks were in the crankcase !

[Charles P]

Was your engine bolted down solid ?
I have been helping a friend with his magneto engine over the weekend albeit a high mileage standard unit,I couldn't believe how many cracks were in the crankcase !

No. bolted down at the front and with a long bolt and old valve spring in the near side rear.
I bet my crankcase now has cracks!

c

[Austin in the Shed]

Discounts the twisting theory then.

[dickie65]

Oh Dear,
Sorry you had such a bad time at Prescott.
I did not realise it was that bad when I poked my nose under the bonnet.

Best of luck with the repairs.

Richard

[Tony Betts]

Pistons are 57.5mm. It's a mid 30's block. It looked thin to me as well.
There weren't extra studs in the valve chest - it's just broken across there.


Charles

Hi Charles,

May be good to try get a vintage block, I understand the material is closer to chromidium.

Would hopefully be stronger.

What are the two drill holes between 1&2 and 1&4 that's were I thought you might have put extra studs.

Tony.

[Ruairidh Dunford]

I thought the same Tony.

I have seen similar on two engines in the last year - both were bored right out and had high lift camshafts with incredibly strong valve springs (Maxi perhaps?) - I presumed that the blocks were being asked to do too much coupled with thin walls. Neither had done more that 4000 miles since full rebuild.