another rebuild (with questions)

[akeboshi]

hello,

so the first l28 engine i rebuilt for the z was also the first motor i have ever rebuilt. to make it short i didnt do the break in properly so the rings didnt seat right and i wiped my cam also. it currently runs but i would like to rebuild another one to better quality so i know that it will last.

 

so i buy a used engine from craigslist and the guy says he pulled it after he ran it. it looked clean and he had a new turbo motor sitting in his bay so i buy it. i was debating whether to just run it or tear it down for a rebuild. im glad i decided to tear it down cuz it was f@#cked up. every cam lobe was ground down taking the rockers with them in the process and the cam tensioner was in the oil pan along with chain guide rubber and teeth from the cam sprocket and sealant sucked against the pickup. these were not the only surprises i found.

there were pistons stamped 050 on them. they measured roughly 86.5mm so im assuming the stamp means .05mm over.

the bigger surprise was the valvetrain was shimmed up. i took measurements on all the shims and they are as such

cam bearing shim=.018 and there were two of them

inner valve spring shim=.038

outer valve spring shim=.038lash pad=.117 (i thought these were supposed to be .120 stock?)

 

so my question is how can i tell how much they have taken off of the head? i will cc the chambers and pistons soon to calculate c/r but until then i would like to hear input.

also another question (its stupid but ill ask it anyways) would it be ok to sandblast the gasket surfaces of the head and block and not machine them? just something i have been wondering.

one more question is how do i know how much bigger lash pad to get to center my valvetrain back up. i noticed it was alittle off center. not much but i would like to get it back centered again.

 

thanks for the support,

marcus

 

 

p.s. guess that piston!

[rossman]

Have you thought about getting a copy of How to Rebuild Your Nissan/Datsun OHC Engine?