scrap or rebuild?

[Sparks]

well i got the engine apart today. i ran it way too hot without coolant a couple months ago and then dumped some in so i could go back to work. bubbled out of control and when i started it nothing but white smoke out the exhaust. i have drained all the coolant from the oil and cleaned out the cylinders. my headgasket was still intact with no indication that it failed. a straight edge to the head reveals that it is no longer flat. while im prepared to have that sent off tomorrow for a shave but i found two cracks in the usual spot between #2 and #3 cylinders. cracks go from the water passage to the headbolt threads. these are the only two cracks on the block. im unsure if they are new or have been there for a while. my question after reading other posts is should i scrap the block or would it be okay to run it the way it is? thanks in advance for the input.

 

-Sparks

[datzenmike]

Severe over heating can break the top rings and piston lands... not saying this is the case here though. Are any of the cylinders scored?

 

Cracks were likely there all along and if you think about it, if water could get as far as the bolt hole where's it going after that anyway.? Can't go down into the block... cant go sideways because of the gasket.... cant go far upwards as there is a big washer and bolt head torqued to 60 ft lbs onto soft aluminum.

 

Mill the head or replace it, throw a new gasket on and see what you have when restarted.

[Sparks]

cylinders still have the hone marks in them. not a scratch or gouge anywhere.

[datzenmike]

...and it was running fine before? not an oil burner, good compression?

[Sparks]

running great before this. my radiator has a pinhole in it and i work on boats and left it parked for 5 weeks. i imagine the coolant had enough time to leak out in that period. i didnt do a compression check before this happened but it ran great. plenty of power. didnt burn any oil. it has a leak from the timing cover and a slow one from the rear main but didnt burn any oil.

[datzenmike]

Then worth investing in a shave and a gasket. Way cheaper than replacing or rebuilding.

[Sparks]

ill give it a go and post a follow up after i get the head back. thanks for the feedback

[Sparks]

threw the head back on there, dumped some fluids in there and it fired right up. have an exhaust leak but thats because i had to reuse the gasket. the one in the kit was for round port. on my way to the store to get the gasket. feels good to have it back. thanks for the help.

[banzai510(hainz)]

Get a new Radiator!!!!!!!!!!!!!

[datzenmike]

Did you mill the head? or did it need it? When over heated it's almost guaranteed to blow the gasket and usually the head is warped. It's also possible that it isn't and only time will tell if it blows again right away.

 

I swapped an L20B into my 521 that a buddy had changed the gasket on. It lasted 3 weeks. I figured he did a poor job and re did it....lasted a month. Took it back off and checked it this time and it was warped. Lesson learned.

[Sparks]

the head was pretty warped. the shop milled it down so its completely flat now. new gasket and fluids and its up and running again. im trying to find a good radiator for it but not sure what to order. seen a few on ebay for around 250 but they look to have different necks on the lower outlet. i can order one through napa up here but it will end up costing more than one of those aluminum ones off ebay.

[datzenmike]

What about a rad shop? They use your top and bottom tanks and replace the rest.

[Sparks]

there arent any rad shops here in town. i may be able to make it to anchorage if i found one there. having a datsun in alaska makes it difficult to get parts. ordered a intake gasket and thats going to take 7-10 days to make it up here.

[datzenmike]

Japan is closer.....