Are the holes in the block for 5.3 iron & Ls1 the same?
Are the holes in the block for 5.3 iron & Ls1 the same? I am going to swap a 5.3 turbo into a 91 coupe mustang & wanted to go the 4.6 k and modded 4.6 mounts route, but i thought I remembered reading that the mount holes on an iron 5.3 and the aluminum Ls1 were different. Anybody ran into this? Can you do a similar mod to the factory mount and make it work on a 5.3? If I need to search just put me in my place, but i searched a couple ways, & found no definitive answer.
As far as I know, there are only two bolt holes that are different between an LS1 and a 5.3l, and both of those are for the alternator mount. The LS1 has an alternator mounting boss the 5.3 doesn't have, and the LS1 has a hole tapped for the alternator bracket that is untapped on the 5.3.
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The first two posts in this thread would seem to suggest otherwise?
Tipsy
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To my knowledge the motor mounting pads for gen3/4 are all basically the same, 4-bolt holes. Not sure about LS7/9 but they are LS blocks so i'd bet they are the same too. Accessory mounting holes are slightly different as mentioned in previous posts.
Last edited by fox12303; Aug 24, 2013 at 09:44 PM.
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The four motor mount holes on the LS motors are the same. They are four holes towards the front of the engine, on a square pattern of 78mm x 112mm.
The 4.6L motor mount leg which gets extended is not a motor mount boss, it is a block ground hole, which is coincidentally drilled and tapped for the same thread on the aluminum blocks. The iron blocks have this hole drilled and tapped, this is why the adapter plates were invented. Also the hole spacing on the mod motor mounts is not 78mm in the vertical, you have to elongate one of the holes.
The 4.6L motor mount leg which gets extended is not a motor mount boss, it is a block ground hole, which is coincidentally drilled and tapped for the same thread on the aluminum blocks. The iron blocks have this hole drilled and tapped, this is why the adapter plates were invented. Also the hole spacing on the mod motor mounts is not 78mm in the vertical, you have to elongate one of the holes.
The four motor mount holes on the LS motors are the same. They are four holes towards the front of the engine, on a square pattern of 78mm x 112mm.
The 4.6L motor mount leg which gets extended is not a motor mount boss, it is a block ground hole, which is coincidentally drilled and tapped for the same thread on the aluminum blocks. The iron blocks have this hole drilled and tapped, this is why the adapter plates were invented. Also the hole spacing on the mod motor mounts is not 78mm in the vertical, you have to elongate one of the holes.
The 4.6L motor mount leg which gets extended is not a motor mount boss, it is a block ground hole, which is coincidentally drilled and tapped for the same thread on the aluminum blocks. The iron blocks have this hole drilled and tapped, this is why the adapter plates were invented. Also the hole spacing on the mod motor mounts is not 78mm in the vertical, you have to elongate one of the holes.
Tipsy
Last edited by TipsyMcStagger; Aug 24, 2013 at 08:45 AM.
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Okay, but in this post, it appears the OP is indicating that the lower left hole (the one covered by his hand) does not align ("they line up in the 2 holes pictured and the one bottom hole." What am I missing? Is that lower left hole (in the mount) what you're saying needs to be elongated?
Tipsy
Tipsy
The motor mount holes on an LS are 78mm vertical x 112mm horizontal. Mod motor mounts (which are not AJE mounts) are not on 78mm vertical centers, but they are so close that one hole can be slotted to reach the 78mm vertical center.
LS motor mount bosses are the same regardless of gen3 / gen4. I don't know anything about gen5.
Honestly, I hate to say this, but search the forum. That issue has been known about with the AJE mounts for years. I can't explain to you why AJE makes what I consider to be stupid decisions.
The motor mount holes on an LS are 78mm vertical x 112mm horizontal. Mod motor mounts (which are not AJE mounts) are not on 78mm vertical centers, but they are so close that one hole can be slotted to reach the 78mm vertical center.
LS motor mount bosses are the same regardless of gen3 / gen4. I don't know anything about gen5.
The motor mount holes on an LS are 78mm vertical x 112mm horizontal. Mod motor mounts (which are not AJE mounts) are not on 78mm vertical centers, but they are so close that one hole can be slotted to reach the 78mm vertical center.
LS motor mount bosses are the same regardless of gen3 / gen4. I don't know anything about gen5.
Thanks for clearing that up.
Tipsy
