Tech Articles

Location, Location, Location: Swapping Mounts to Find the Best Engine & Transmission Position

Even a fraction of an inch when positioning your race car’s engine and transmission can cause (or solve) a lot of fitment and clearance problems. (Image/Wayne Scraba)

Everyone’s heard the old real estate mantra “Location-Location-Location.”

And while that’s obviously important in the property game, that pithy statement also holds true for a car’s engine and transmission—even if those aforementioned locations are separated by fractions of an inch.

In fact, you might actually be surprised at how important those little fractions can be.

Meet Our Chevy Nova Test Subject

Case in point is my long-term Nova project. It’s a simple combination using readily available parts: a big block Chevy backed by a four-speed gearbox. It uses correct 1970 Nova engine frame mount brackets, an appropriate (and correct) big block, stick shift transmission crossmember, and what seemed like correct motor and transmission mounts.

It’s not my first rodeo with these cars—I’ve had five 1969-1971 Novas along with an equal number of first-gen Camaros over the years. Before each build is complete, I check fitment in critical areas like valve cover to wiper motor, headers, hood clearance, modified clutch linkage, and so on.

So, I mocked up an engine and transmission and slid it into place. What could possibly go wrong?

As it turns out, plenty. The first thing was the Moroso motor mounts I thought were correct for the application didn’t fit. They were too wide for the frame mounts and too short. So out came the engine and I replaced the mounts with known correct Chevy OE-style clamshell mounts. The engine fit nicely. But the top of the transmission case touched the tunnel.

What was going on?

It ended up being the rubber transmission mount. This was a low mileage component I had from a six cylinder, three-on-the tree Nova. It was a wee bit too tall. Oops. Something was up—no pun intended.

Swapping Motor & Transmission Mounts

Back to the drawing board. For my purposes, I choose to use a mix of rubber and steel mounts. Instead of using two rubber motor mounts, and then using some sort of device (such as a turnbuckle) to tie the engine down on the driver’s side, I prefer to replace the driver side mount with a steel example. With this setup I regularly use a rubber transmission mount. Fair enough. But that doesn’t explain the fit issues.

As a result of this, I started to do some research, and what came out of it might even surprise grizzled veterans of the vintage Chevy world. First things first. We (there was now more than me just involved) pulled a bunch of mounts out of Summit Racing’s vast inventory:

  • ANI-2268 Anchor Industries Transmission Mount
  • ANI-2378 Anchor Industries Transmission Mount
  • ENS-3-1108G Energy Suspension Transmission Mount
  • ENS-3-1158G Energy Suspension Transmission Mount
  • PIO-622378 Pioneer Automotive DEA Products Transmission Mount
  • MOR-62510  Moroso Solid Steel Motor Mount
  • MOR-62515  Moroso Solid Steel Motor Mount

We mixed those pieces in with the parts already used on the Nova:

  • MOR-62530 Moroso Solid Steel Motor Mount
  • GM 3928392 Chevy Transmission Mount
  • GM (style) 2288 Chevy Big Block Motor Mount

As mentioned previously, the car has 1970 big block Nova frame mount brackets (and the same frame mount bracket set is used on 1969 Camaros); part number 3950113 for the driver side; 3950114 for the passenger side. These are one of the many (later), superseded part numbers. They measure approximately 2.355 inches wide, with the driver’s side taller than the passenger side. The engine is also offset to the passenger side from the factory.

Big block frame mount brackets for 1967-68 Camaros and 1968 Novas differ.

Here’s something else to ponder: If you don’t use the right mix of frame mount brackets, motor mounts, and transmission crossmember in a Camaro or Nova, you’ll end up with header clearance issues, z-bar clutch linkage issues and potential oil pan/steering clearance issues.

Comparing Mounts to Find the Right Clearance Combo

The first difficulty to arise is the Moroso catalog. It doesn’t actually list a solid mount application for 1969 big block Camaro models, and it appears the information for 1969+ big block Novas is wrong. The catalog lists a 62530 steel motor mount for the application. That mount is approximately 2.66 inches wide (on the i.d.). That’s more than a quarter-inch too wide for the frame mount bracket. And it is also shorter than the stock mount. The stock motor mount measures 2.125 inches tall (from the c/l of the bolt hole to the block motor mount surface). The Moroso 62530 motor mount measures 1.75 inches tall.

The correct motor mount part number from Moroso for this application is a number 62510. It measures 2.390 inches wide, and is the same height as stock at 2.125 inches. As expected, it places the engine in the stock position. It also happens to work happily in the Nova combination we’re using as the example.

Fair enough, but there’s also another similar mount that will effectively raise the engine. And that’s the Moroso number 62515 in our parts list. This mount is also 2.390 inches wide, and it is marginally taller. The big difference is the bolt hole (where it attaches to the frame mount bracket) is offset 0.550-inch. In practice. This would move the engine up (higher in relation to the frame mount bracket) by roughly a quarter-inch.

Now, to throw a little curve into engine heights, Moroso offers a pretty neat mount shim kit, under part number 62535. These shims install between the motor mount and the cylinder block. The kit includes two shims in each thickness of 1/16 inch, 1/8 inch, and 3/16 inch. The purpose here is to allow you to raise the engine slightly in order to compensate for oil pan, steering linkage and header interference.

While the above provides a ton of options when it comes to engine location (height), none of it explains why the transmission kissed the tunnel in the our Nova.

According to vintage Chevy info, all manual transmission Novas use the same rubber mount. But when we researched different mounts, it became rather clear there are several different options—and they’re not all the same when it comes to dimensions. Check it out:

We laid out all of the mounts from our lists above. The “standard” (if you care to call it that) is the OEM 3928392 mount we had. It fits, and is used on just about every vintage GM stick shift transmission application on the planet. It also sees use in some Powerglide and TH350 applications. In terms of thickness, this mount measures 1.825 inches.

Next up was the Anchor 2268 mount. This time, the thickness measurement was actually larger at 1.880 inch. For our application, this clearly wasn’t going to work.

The Anchor 2378 transmission mount measured 1.805 inches, so it’s 0.020-inch shorter. We were going in the right direction for our Nova.

The fourth transmission mount out of the Summit Racing stockpile is a Pioneer 622378. This mount measures in at 1.800 inches thick—again, slightly shorter, and moving in the right direction. Something to keep in mind here, is all of the above rubber/steel transmission mounts will likely compress a bit following installation.

The last two mounts in our roundup are composite urethane/steel designs from Energy Suspension. These mounts include a separate steel reinforcement plate that must be installed with the mount. In terms of measurement, the ENS-3-1158G mount measures 2.110 inches thick, however it looks like this mount will compress down to approximately 1.85-inches following installation. There are two raised “humps” in the mount that we suspect will flatten out once tightened down. We’ll toss in some photos below so you can see what we’re talking about here.

Energy Suspension’s ENS-3-1108G is a special mount. It is designed to be shorter than the others. In terms of measurements, it works out to 1.685 inches thick, including the reinforcement plate. Compressed, it appears that number will shrink right down to 1.495 inches. That’s a full 0.330 inch (slightly more than 5/16 inch) less than the OEM mount.

It’s perfect for our application. But it’s also perfect for combinations where you need to juggle the pinion angle.

The Perfect Mounts for the Perfect Fit

As you can see, there’s quite a number of little variables that can be juggled when installing an engine and transmission. Those tweaks can spell the difference between a perfect fit and a lot of aggravation. While we used a Nova for this comparison, we’re sure you’ll find similar differences in other cars—GM or otherwise.

Location-Location-Location? It’s pretty darned important. For a closer look at all the mounts we talked about in this article, check out the photos below.

***

All of these mounts, motor and transmission, can play a huge role in determining the location of the engine and transmission in a car. While our application is a 1970 Nova, the same approach can be used for countless other models. (Image/Wayne Scraba)
Here’s our motor mount roundup. It includes a set of stock-style GM mounts and three different Moroso motor mounts. (Image/Wayne Scraba)
Laid out in a row, it’s easy to see the differences in mounts. (Image/Wayne Scraba)
As described in the article, it’s possible to juggle mounts and to shim them to change the engine location. (Image/Wayne Scraba)
A big part of the mount puzzle is determining which frame mount bracket to use. (Image/Wayne Scraba)
These frame mount brackets for a big block move the engine over and raise one side in a stock Nova and Camaro application. We talk about it in more detail in the article. (Image/Wayne Scraba)
This is the group of transmission mounts we picked from Summit Racing inventory. (Image/Wayne Scraba)
The stock GM mount is on the left. Note the height differences. (Image/Wayne Scraba)
Energy Suspension urethane/steel composite transmission mounts are engineered with a reinforcement plate that must be included during the installation. (Image/Wayne Scraba)
Here’s a look at the little raised humps found on the Energy Suspension mounts. They’re pliable and we suspect they will compress when torqued down. (Image/Wayne Scraba)
This is the problem solver for us: the “short” Energy Suspension mount mentioned in the text. It allows a Jerico transmission case to clear the tunnel in our Nova. It could very easily be a solution for your car too. (Image/Wayne Scraba)

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