Mf 65 mark 1 4-192 motor , broken rocker arm , valves touch piston

[Hendo1]

Just rebuilt mf 65 4 -192 motor , A shop done most of the work , new liners piston rings , con rods new crank they done all the work plus assemble bottom end , they had to weld water jacket on block then shave block , head was fully rebuilt valves guides seats shaved as well to get clearance they had to lathe top of pistons , I assemble rest of motor crank set on top dead centre on flywheel all timing marks line up right , tractor started straight up took for a drive a couple of ks stop start good motor done about 1 hour of running had it idling 10 mins next started popping through air cleaner , pulled rocker cover off found number 4 exhaust rocker broken removed head found vales guide split on the spring side plenty of oil getting to top end nothing seize or stiff plus you can see on number 2 piston out line of inlet valve burn plus number 4 where valve has been touching piston pop may be bent inlet valve , Dropped parts off at shop who done the work talked to the bloke that did the work he doesn't know what caused it at this stage , I pulled the tractor apart to recheck the timing marks after 1,999 turns all the timing marks lined up top dead centre on flywheel anyone has this trouble

 

[Phillip w]

I have not run into this trouble. If I had to just take a wild guess I'd be leaning towards the head. Maybe the tolerance were off a little when the head was rebuilt.

 

[Hendo1]

I have not run into this trouble. If I had to just take a wild guess I'd be leaning towards the head. Maybe the tolerance were off a little when the head was rebuilt.

Thanks Phillip yes I am thinking the same and not enough clearance when head block piston shaved , there saying the new valve springs maybe weaker than the gen ones and where the collards set that to long and they want to machine down there gen ones looks like the valve guides are to long as the valve where the collards set are hitting the valve guide that cracked one of the valve guides

 

[Spanner]

I'd say it's a mathematical issue. 'Someone' hasn't done their arithmetic correctly. Measurements must have been missed on the length of the valve guides and also the lift on the cam given the shaved head and block. They haven't taken enough off #2 piston either? All the pistons should have been the same. i.e. all hitting their valves or all missing.?
Bad luck for you anyway. I'd expect the engine reconditioning shop to rectify the issue back to a running engine for you. Minimal charge, if any.

 

[Hendo1]

I'd say it's a mathematical issue. 'Someone' hasn't done their arithmetic correctly. Measurements must have been missed on the length of the valve guides and also the lift on the cam given the shaved head and block. They haven't taken enough off #2 piston either? All the pistons should have been the same. i.e. all hitting their valves or all missing.?
Bad luck for you anyway. I'd expect the engine reconditioning shop to rectify the issue back to a running engine for you. Minimal charge, if any.

Thanks Spanner thinking the same , went into top shop today took old valve springs in to see if they are stronger than the new ones that were fitted , I asked about valve guides if they were left to long was told machine checks and cuts them down to right size and I asked about valve length said all right height, yet they want to machine valve collar so it doesn't hit valve guides but everything in spec doesn't add up maybe the valve seats are not right as they replaced them