87burb
08-30-2009, 12:49 PM
well I found 3 motors for my burb (earlyier post) went and looked at them
two have the casting 12555506 which means 90+ casted means good block not prone to crack... but they look like a 6.5 how do I tell the diffence it has the 6.5 fuel filter with a non egr intake (out of bread trucks) and the cdr is on the valve cover... the other motor is a rebuilt unit with the casting 14022660(or 650) so stay away from it it is the older casrting right....
thanks
mattthebrat
08-30-2009, 07:12 PM
The 506 is a 6.5 casting; 96+ I believe. They were used a ton in N/A form in the bread trucks.
The 660 is an older (mid 80s) block, not necessarily a bad block, I know many guys who have build stout, long lasting motors out of 660s.
The one drawback is that it has the rope style rear main, which is alot harder to change should you ever need to.
randomid25
08-30-2009, 07:18 PM
The 506 is a 6.5 casting; 96+ I believe. They were used a ton in N/A form in the bread trucks.
The 660 is an older (mid 80s) block, not necessarily a bad block, I know many guys who have build stout, long lasting motors out of 660s.
The one drawback is that it has the rope style rear main, which is alot harder to change should you ever need to.
a 506 gm is a late model 6.5 oil squirter block. From what I've read, they are the worst to crack. 660 blocks are early blocks from 83 to say 89. Mostly 6.2's and they seem to be pretty good blocks. 599 and 506 blocks are one piece rear main seals vs the 660s two piece. Those are the differences that I'm aware of with those. Good luck.
IamDave0887
08-30-2009, 10:28 PM
The 506 is a 6.5 casting; 96+ I believe. They were used a ton in N/A form in the bread trucks.
The 660 is an older (mid 80s) block, not necessarily a bad block, I know many guys who have build stout, long lasting motors out of 660s.
The one drawback is that it has the rope style rear main, which is alot harder to change should you ever need to.
506 was the 98 and up 6.5 block. the factory ones were known to crack, but the new 506 cast block from Navistar(diamond in teh valley) are much stronger from what i've read. There's also the 929 and the 141 6.5 blocks as well.