Post by 99for200bucks on Apr 19, 2016 20:17:33 GMT -6
Hi,
Inexperience with the northstar has led me to this point, a 4.6 swap. Since I've already purchased
a 275 H.P. 4.6 and I've already removed enough items from the 4.0 to consider it fairly well on it's
way to a pull from the top, Ive decided to go ahead and do the swap, whether or not the 4.0 has a
crack in the block.
Since I already have them, I will be using normserts and ARP head studs on the 4.6 HG repair. Some
info on this particualr 4.6... I could plainly see, during the pull from the deVille at the junkyard, the oil
seeping from the headgaskets on the inside edge of the rear cylinder bank. It had leaked enough to
cause a small lake under the intake. This oil had leaked out the starter hole (either with the starter
still in place, after I pulled starter, or when was tilted during removal and transport to my garage, or
most likely combination of all of the above) and a small drain hole next to the starter hole leaving a
trail from those holes, to the bottom of the pan on the outside next to flexplate. There is very little
residue anywhere else except for maybe the front timing cover/front crank seal to indicate this engine
is leaking from the pan or the case halves.
There has been a major leak repair done on this engine IMO. There is a sealing substance around
both lower interfaces of the block bottom end. There is also this part number in the back of the
engine: #12568025 (had to use a magnifying glass to see that lol). This is the current part number
listed at this website (and many others) as the current and absolute best rear main seal for my
particular year (1999) of an LD8 northstar:
www.northstarperformance.com/partnumbers.php
It is my understanding that GM did not use any sealer, just gaskets while assembling that lower end
during that year, yet mine has sealer. Also, the engines produced that year never had the updated
rear seal (cartridge type seal). I'm 100% sure that this engine has had a bottom end re-seal. I will
make an assumption here and say that it has been re-sealed within the last 25k or so miles based on
the evidence that they usually leak at around 75k or above and this one was @ 109k miles. Whether
the job was done correctly or not is something I'm not willing to add the expense of yet another
oil manifold plate and a set of TTY main bearing bolts. I'm also positive that plate has been replaced
with the upgraded version since the main seal was, and that plate I believe is a mandatory
replacement if pan is removed. Add in the increased chance of screwing something up on assembly,
leaving me with a spun main is just not worth the minor piece of mind a double check would entail.
I have sourced all the locations for any residue below the case halves and determined they are from
somewhere else. Those locations being the starter hole/drain hole and the front timing cover/crank
seal. It is for these reasons and several others that I will NOT be doing a bottom end re-seal on this
engine. Pics to follow sourcing oil residue.
Let the fun and pain begin!! By that I mean I love doing this stuff, but I'm getting old...
Paul.
Inexperience with the northstar has led me to this point, a 4.6 swap. Since I've already purchased
a 275 H.P. 4.6 and I've already removed enough items from the 4.0 to consider it fairly well on it's
way to a pull from the top, Ive decided to go ahead and do the swap, whether or not the 4.0 has a
crack in the block.
Since I already have them, I will be using normserts and ARP head studs on the 4.6 HG repair. Some
info on this particualr 4.6... I could plainly see, during the pull from the deVille at the junkyard, the oil
seeping from the headgaskets on the inside edge of the rear cylinder bank. It had leaked enough to
cause a small lake under the intake. This oil had leaked out the starter hole (either with the starter
still in place, after I pulled starter, or when was tilted during removal and transport to my garage, or
most likely combination of all of the above) and a small drain hole next to the starter hole leaving a
trail from those holes, to the bottom of the pan on the outside next to flexplate. There is very little
residue anywhere else except for maybe the front timing cover/front crank seal to indicate this engine
is leaking from the pan or the case halves.
There has been a major leak repair done on this engine IMO. There is a sealing substance around
both lower interfaces of the block bottom end. There is also this part number in the back of the
engine: #12568025 (had to use a magnifying glass to see that lol). This is the current part number
listed at this website (and many others) as the current and absolute best rear main seal for my
particular year (1999) of an LD8 northstar:
www.northstarperformance.com/partnumbers.php
It is my understanding that GM did not use any sealer, just gaskets while assembling that lower end
during that year, yet mine has sealer. Also, the engines produced that year never had the updated
rear seal (cartridge type seal). I'm 100% sure that this engine has had a bottom end re-seal. I will
make an assumption here and say that it has been re-sealed within the last 25k or so miles based on
the evidence that they usually leak at around 75k or above and this one was @ 109k miles. Whether
the job was done correctly or not is something I'm not willing to add the expense of yet another
oil manifold plate and a set of TTY main bearing bolts. I'm also positive that plate has been replaced
with the upgraded version since the main seal was, and that plate I believe is a mandatory
replacement if pan is removed. Add in the increased chance of screwing something up on assembly,
leaving me with a spun main is just not worth the minor piece of mind a double check would entail.
I have sourced all the locations for any residue below the case halves and determined they are from
somewhere else. Those locations being the starter hole/drain hole and the front timing cover/crank
seal. It is for these reasons and several others that I will NOT be doing a bottom end re-seal on this
engine. Pics to follow sourcing oil residue.
Let the fun and pain begin!! By that I mean I love doing this stuff, but I'm getting old...
Paul.