head gasket blown twice

[EzyQ]

looking for some advice

my son & I have just built a 1310cc A+ build spec is as follows

+40 bore with +40 standard pistons
mini spares Evolution 1 cam
Crank was ground +10 with all new bottom end shells
head was reworked with new inlet valves & reground exhausts copper head gasket installed
Carb is HIF 44
Manifolw exhaust system

engine was in and running fine although some fine tuning with timing and emmisions was required, first off had some coolant flow issues, suspected air lock and thermostat which was rectified

took the car a test drive, big bang and went off a cylinder and lost all its water so immediately shut it off
on investigation found a rad hose had burst and the head gasket was now sticking out between the head and block just above the water pump

head off and gasket was totally destroyed

everything cleaned and inspected and new copper gasket fitted
car running again idling fine revving ok coolant circulating etc took for the test drive got a bit further this time then bang again off a cylinder but didn't loose any water

had a look and the head gasket blew again basically in the same place as last time

head nut torque ive been using is 50ftlbs and every time ive went to remove the head they just don't feel tight enough ?

after installing the gasket the 2nd time I did notice an oil leak from the corner of the head beside cylinder 1 which wasn't there initially

before I striped the head off last night I checked compression on 3 cylinders 4 & 2 was 130psi 3 was 100psi

[EzyQ]

davejf said:

Any 1275 gasket should fit. Mines a 1293 and there is clearance. That torque figure looks correct. Did you start up, warm up, allow to go fully cold and re-torque as you don't mention that? Could be your issue as after the first heat cycle and everything expanding its amazing how much extra you can tighten them!

that's one thing I haven't done, the engine is about ready to lift out as also discovered an oil leak from the timing casing and cover so plan to rectify these while the engine is out as impossible to do in place

[EzyQ]

Lotobear said:

Have you checked the head and deck for flatness?

block was decked and head skimmed prior to the build not checked again since the first gasket blew

[EzyQ]

gottans said:

Is the ignition timing correct?

I had something similar happen on a 1380 A-series engine that was down to wrong timing, burnt through the gasket to the water jacket and hydraulic'd, blowing the gasket out. Luckily cooper S rods are very strong.

since ive had it running one thing ive not managed to check was the timing an just been adjusting it by listening hence ive went and bought a timing light now so I can check correctly once I have the engine back together and back in the car

[EzyQ]

Not yet been too busy. But I have everything to start the rebuild again so planning doing that next week.

[EzyQ]

Update

Rebuilt the engine new copper head gasket, sorted out the leaking timing cover etc

Stuck the engine in set the dizzy and started first time used my timing light and set to 10deg

I've since run it for 160miles at various speeds with revs as height as 5750rpm

And so far no issues.

Thinking I'd set the timing wrong causing det which blew the gasket