After third try, LS3 STILL won't go in

[Rybar]

Todd is correct, I wrecked two sets of the poly mounts before switching to solid. But the mounts felt fine to me, I never noticed any issues until a buddy pointed it out to me, so maybe the preload plates are needed? But I had the same issue as the OP, the motor wouldn't fit with them.

[ModernMuseum]

Originally Posted by Rybar

Todd is correct, I wrecked two sets of the poly mounts before switching to solid. But the mounts felt fine to me, I never noticed any issues until a buddy pointed it out to me, so maybe the preload plates are needed? But I had the same issue as the OP, the motor wouldn't fit with them.

Hrmm...I'm on the fence now

The only difference I can foresee if I don't go with the pre-load plates is the point of contact. Since the pre-load plates have the ridge in the middle, the only part of the pre-load plate that touches the S&P adapter plate is in the middle. The pre-load plate actually gets warped a little when it is tightened down.

However, without the plate, all of the rubber section in the middle will be touching the S&P adapter plate. It will still be crushed a bit (so I'm guessing it will be pre-loaded), but the engine mount's contact surface will be the full area of the surrounding metal as well as the full rubber area.

With the pre-load plates, the contact surface between the engine mount and adapter plate is the ridge in the middle and the outer perimeter where it bolts down.

[AM.MSCL]

I have been told that the firebirds have a different centerlink then the Camaros and it sits in a slightly different location by about a 1/4" towards the firewall. Due to this fact the Oil pan will sit on it and not allow the engine to fully align with the bolts on the mounts. The Oil pan has to be modified to clear the centerlink.
Hopefully you verified that the oil pan is not hitting something already?!

[ModernMuseum]

Originally Posted by AM.MSCL

I have been told that the firebirds have a different centerlink then the Camaros and it sits in a slightly different location by about a 1/4" towards the firewall. Due to this fact the Oil pan will sit on it and not allow the engine to fully align with the bolts on the mounts. The Oil pan has to be modified to clear the centerlink.
Hopefully you verified that the oil pan is not hitting something already?!

You are correct. The firebirds and camaros have different center links. The firebird center link is more or less straight and the camaro link has a slight bend in it. I have already taken the center link out and have a camaro center link to put in its place.

I have a champ road racing pan, and I am pretty sure it will clear the bottom cross-member (and hopefully the camaro center-link). I have been told that the 69 sub-frame is the same as a 68 camaro sub-frame.

[ModernMuseum]

Ok, I got the "thin" or "regular" mounts in from S&P. There don't appear to be any dimensional differences between them and the Energy Suspension mounts. The "regular" type just have the back plate molded into the rubber as a single piece, but after several measurements, they appear to be the same dimensionally.

I guess my only option is to use the Energy Suspension mounts and leave the back compression plate off. Hopefully this will mate up and not shorten the life of the mount. I don't really see how it would shorten the life since it's mated to the adapter plate though. I just foresee a slightly different loading on the rubber part of the mount, since the rubber will be flush with the adapter plate instead of the wedged back plate being present.

[Rybar]

Or just run solid mounts

[Vegas69]

This all jogged my memory. Energy mounts are about an 1/8 taller than a factory rubber mount.(That's 1/4" total) 302/350 rubber factory mounts are interlocking as well. Solid mounts have there pluses and minuses.