Cracks In 4K Heads- Had It Happen??

[altezzaclub]

The gold-coloured XX KE70 I bought recently had a leaking head gasket, it always started on three cyls then picked up the 4th after 10-20seconds, then ran fine all day.

 

After being away for a couple of weeks in The Girls KE70 I checked the water in the gold one and saw it was down, and the battery was flat, so I filled the rad up and charged it o'night.

The next day the water was down again but the oil was overfull.. :o

 

Off with the head and I could see the mark between 2 and 3 where the gasket wasn't sealing, so off to a head shop. They ph'd and said they'd found a crack in the head going outwards from a valve seat, although I haven't driven the 100km round trip to pick it up yet.

 

Has anyone else had a head crack?? I thought they just warped on these motors.

[dannyl]

i was helping the church pastor with his 4ye... saw a leaky pump, sticky stat, and a head cracked. it was one of those panel van types.

the engineers designed the head with a weak spot between the valves on purpose because the temp it takes to crack it.

if the customer is going to knowingly keep driving after it overheats, this "fusing" of the head makes it quick and easy found without magnafluxing or pressure testing. some can be welded, baked and reused if there are no cores avail. and they pass the savings on to the driver. good for the maker.

[ke70dave]

Fracture mechanics ;)

 

A crack will start at an imperfection in the grain structure of the aluminium. The crack will proporgate when put under stress and off it goes until it meets the edge of the aluminium.

[altezzaclub]

the engineers designed the head with a weak spot between the valves on purpose because the temp it takes to crack it.

 

I reckon there's a crack between the valves in Mayo's head that Steve has being skimmed as we speak. There's only a couple of mm between the valves, so maybe it goes nowhere. Time will tell with that one. I know that one was driven around for quite a while with the head gasket blown, in fact until it couldn't be driven anymore.

[dannyl]

when the machine shop fixes and or bakes a head they guarantee it. a used one from piknpull is your best money tho. of course the maker wants it to be new, and the mechanic just wishes he could get it out of his stall so a paying customer can pull in.

[Banjo]

From my reading aluminium "ages" just like most metals over time. A head from a K series, now 30 -40 years "olde", will soften, warp, crack, c-o-r-r-o-d-e, & become porous at times, in worst case. Imagine all those heat/cool cycles a head goes through over the life of the engine.

 

I remember reading somewhere once how Chevy guys in the states, used to get olde chevy V8 blocks, grease then inside & out, seal them in thick plastic, & bury them in the ground for several years. Apparently this resulted in a change to the cast iron structure, that made it harder. When they dug them up, they get big bucks for them from serious performance engine rebuilders !

 

Cheers Banjo