Project SR E30: Part 2 – Making Custom Motor Mounts

We start with the tilt. We zero the angle finder on the differential input flange.
We then place the angle finder on the output shaft on the transmission to find the angle difference, and simply jack up the trans to get it perfect.
And to set the yaw, we can just use our calibrated eyeballs. Since the transmission is so close to the shifter hole, it’s very easy to center it visually.

Now that we have the angle of the engine, we can set the height and firewall spacing. The goal is to position the engine as low and as far back as possible, to improve center of mass and increase hood clearance. We first pushed the engine back, until the back of the lower oil pan was just about 2mm away from touching the front of the subframe, and then lowered it until the upper oil pan was resting on top of the subframe.

When setting engine height, you have to take into account motor mount sag. To do this, we used a vice to squeeze the motor mounts until they were about to disintegrate. We measured this stock E30 motor mounts travel to be 6mm. Mind you, a vice will put x100 more force on a motor mount than the weight of your engine ever will, so this is more of a “worst case scenario” measurement, or “maximum travel” as we call it. In reality, with the weight of half an SR, this motor mount will compress about 2mm.

So now that we have our motor mounts “maximum travel”, we raised the engine until the upper oil pan was 6mm away from the top of the subframe. Since we’ve done quite a lot of moving around now, we double checked and nudged the engine around to make sure the center, yaw, roll and tilt were still spot on.

Now it’s time to fabricate. Here we have an E30 motor mount bracket on the left, and SR motor mount bracket on the right. Since they are kind of similar in shape, we decided to just “merge” them together instead of making something from scratch.
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