Motor and Trans Mount

Updated 07-Sep-2003


General Information:

My goal is to get the motor as far back and as low as possible without having the oil pan below the bottom of the subframe while maintaining proper driveline angle.



Initial test fit in a spare junk subframe with AC and Alternator attached to LS1. The engine will not fit low enough or far enough back without notching the subframe for the AC and Alternator. I'm trying to get the motor as low and as far back as possible for best weight distribution.

A few views of my first generation mounts, these are made of 1/4" angle iron. The final version will be made of 1/4" steel plate. Quite a bit if time went into modifying the mounts to get the motor centered with the rear end, level across the chassis and a 2.5 degree down angle. The pinion angle as it sits is 0 degree so I will most likely have to use 2 degree shims under the leaf mounts to get it to point up. I probably have over 40 hours in just this task and I'm just going to use these as templates. The LS1 must have been in and out of the car at least 20 times. I'm glad I pulled the hood, fenders and nose off first, it made it much easier. The last is a shot of the mounts in one of the many phases of modification you can see all the welds, the reason I am going to make a second version.

This is a shot of the shifter after the first hole was cut in the floor. The final mount has it about 1 inch further to the rear of the car than this. It will almost fit the stock auto console, umm wonder if I can get a shift boot for it.

The stock TH350 trans mount with the tab cut off and installed lower on the crossmember with gussets for support. This looks good but the trans is probably going to be the lowest part of the car, watch out speed bumps!


A view of the trans and crossmember hanging just below the subframe, I don't think this will be a problem. If I move the engine any higher I will have to do major modifications to the trans tunnel. At the height where it sits now I have a 2.5 degree down angle to the driveline which should line up with the pinion angle perfectly after I install 2 degree shims under the leaf mounts.


The plates that will be used for the motor mounts. They are fresh from my plasma cutter with a little touch up on the grinder. These will be welded to another 1/4" plate that will bolt to the subframe.



The notches in the suframe to clear the AC compressor and the alternator. It is going to be a challenge to come up with lines for the AC. The stock '99 pressure line goes under the compressor. This means either a really big notch in the suframe or a custom line, I'll be checking on custom lines this week. The bottom of the alternator is only about 3/16" away from the top of the center link bolt that goes through the pitman arm at full right turn. I should be able to grind this down for more clearance. Since the engine only torques in this direction when the car in in reverse I don't think this will be a major problem. I would have to be a full right lock and working the engine to get it to hit, I hope.


More shot of my final subframe notches for fitting the LS1 in the car. Along with a picture of the boxing plates before final installation. I must have had the LS1 in and out 10 times to get this how I wanted it. All that is left now is final welding.


The hole for the shifter wound up about a quarter of the way into the body support structure for the seats. I had to cut and box this structure to clear the shifter tower.