I am rebuilding an engine out of an '87 GN that was lost to an engine compartment fire. I do not know its history other than it is supposed to have less than 5000 miles on it. On teardown, I found that (i) there was coolant in the oil, (ii) the headgasket on #4 was also blown to the lifter valley, (iii) the block was bored 0.030" over and (iv) the crank has already been turned 10/10.
The cylinder walls still have decent crosshatching but are scuffed on opposite sides perpendicular to the axis of the crank. I suspect that a torque plate was not used when it was bored.
1. Am I correct in assuming that I should have the cylinders honed and refinished with a torque plate to straighten them with a minimal loss of cylinder wall thickness and then use file to fit rings?
2. Could I add some block hardener to try to hold the bottom ends of these thin cylinder walls in place more rigidly before boring/honing/finishing? If yes, how high should I go? The drain and core plugs are basically at the bottom of the water jacket so I'm guessing I'll have to put the hardener in after installing the core and drain plugs. I could drill, tap and install a couple of new drains on both sides to set the level. Anybody done this before?
3. Or is the block toast since the only way to straighten the cylinders is to rebore which will make the walls to thin?
The crank looks it it will need to be turned to 20/20. What main bearing should I use? I can't find the Clevite MS960V and MS960H or the Federal Mogul 107M in a 20 undersize. As far as I know, those bearings only go up to 10 under. Can anybody confirm or contradict this? Is the Clevite MS960P my next best choice then?
Which is better, brass or steel core plugs? I expect to use Evans NPG as my coolant.
All responses and opinions are most welcome!
Thanks in advance,
Sumner (Buzz) White in Houston, TX (sumnerw@flash.net)
P.S. I have problems on another engine with the heads lifting and the head gasket blowing between the coolant passages and the lifter valley. Apparently my tuning skills aren't as good yet as the headgaskets are unforegiving. Anybody ever try pinning the cylinder head to reinforce the deck between the cylinder head bolt holes on the intake side as an alternative to going Stage 2?
The cylinder walls still have decent crosshatching but are scuffed on opposite sides perpendicular to the axis of the crank. I suspect that a torque plate was not used when it was bored.
1. Am I correct in assuming that I should have the cylinders honed and refinished with a torque plate to straighten them with a minimal loss of cylinder wall thickness and then use file to fit rings?
2. Could I add some block hardener to try to hold the bottom ends of these thin cylinder walls in place more rigidly before boring/honing/finishing? If yes, how high should I go? The drain and core plugs are basically at the bottom of the water jacket so I'm guessing I'll have to put the hardener in after installing the core and drain plugs. I could drill, tap and install a couple of new drains on both sides to set the level. Anybody done this before?
3. Or is the block toast since the only way to straighten the cylinders is to rebore which will make the walls to thin?
The crank looks it it will need to be turned to 20/20. What main bearing should I use? I can't find the Clevite MS960V and MS960H or the Federal Mogul 107M in a 20 undersize. As far as I know, those bearings only go up to 10 under. Can anybody confirm or contradict this? Is the Clevite MS960P my next best choice then?
Which is better, brass or steel core plugs? I expect to use Evans NPG as my coolant.
All responses and opinions are most welcome!
Thanks in advance,
Sumner (Buzz) White in Houston, TX (sumnerw@flash.net)
P.S. I have problems on another engine with the heads lifting and the head gasket blowing between the coolant passages and the lifter valley. Apparently my tuning skills aren't as good yet as the headgaskets are unforegiving. Anybody ever try pinning the cylinder head to reinforce the deck between the cylinder head bolt holes on the intake side as an alternative to going Stage 2?
