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Left: Miata "BP" 1.8L engine weighs 348 lbs. Right: Miata 5-spd manual transmission weighs 85 lbs
Some of the weights involved are shown above and below, from weights we have taken. Looks like the 1.8L Miata motor and 5-spd trans together weigh 433 lbs, with accessories. Not bad for an iron block 4 cylinder. By comparison the BMW E36 chassis' 4 cylinder M42 DOHC 4 and Getrag 5-spd are 429 lbs, which is almost identical. The big 5.7L LS1 V8 weighs 457 lbs soaking wet, with all accessories (and has more than
triple the displacement and
triple the power of the Miata 1.8L). The 6 speed Tremec T56 (from the 1998-2001 Camaro) itself is a portly 125 lbs, but it's a big strong transmission with two overdrives. That should give us a 582 lb drivetrain,
if we stick with the T56, or an
extra 149 lbs over stock. The combined "609 lb" weight shown below was indeed for an LS1 and T56 drivetrain with accessories, but also included a stock Camaro engine harness, MAF sensor, and engine computer.
Left: The M42 1.8L DOHC 4-cylinder and Getrag 5-spd is 427 lbs. Right: A fully dressed 5.7L LS1 + T56 at 609 lbs (click to enlarge)
Why do we love the LS1 V8 so much? Well, there are several reasons. It is a compact and light engine, as I mentioned before. It has been used in literally millions of cars and trucks worldwide since 1997, in so many variants - iron and aluminum blocks, and factory displacements that include 4.8L, 5.3L, 5.7L, 6.0L, 6.2L, 7.0L - that are all dimensionally identical. With aftermarket support that dwarfs almost every motor in existence, there are essentially no limits on power goals, which aftermarket engines that can make 8.5L and boosted engines pumping out 2500 hp. A common build is to use a nearly stock aluminum 5.7-6.2L LS1 series engine and make 350-450 whp, with a mild camshaft, good street manners, and great power under the curve. Even "only" 350 whp in a 2500 pound package can be a
total blast at an autocross or track event. A little more displacement and/or compression+camshaft can get you to 500 whp, which is
a LOT of fun.
Our first steps included finding a willing Alpha customer, which we found in Jason Toth. He was eager to become our first test customer and on his own he rounded up this highly optioned, 1999, silver 5-spd Miata that needed a little help and wasn't anything super rare, so it will make a great swap candidate. Once the car was here, we took a ton of measurements and fixed a few little things on the chassis that were going to stay. Then the OEM drivetrain was pulled out so we could take a closer look.
The car was coated in oil underneath from a leaky front seal, so we gave it the full pressure wash treatment under the hood and on the bottom. Once the car was in the air I noticed the relatively large transmission tunnel, so I was pretty confident we could make the Tremec T56 or something like it fit without too much trouble. We might go another direction with the transmission, with two other possible gear box candidates, but I will share more on that soon.
First test fit of our mock-up LS1 and T56 transmission
Once the stock drivetrain was out, we shoved our "mock-up" LS1 engine and T56 into the little car. The initial fit wasn't half bad, but there are two corners in the firewall that really limit rearward movement of the V8 engine's cylinder heads. Our guys cut some small notches back there (which will be covered in steel when the final engine placement is locked down) and re-installed the LS1/T56 drivetrain farther back, and now it looked much better.
Well we're committed now! You can see the corners we trimmed to make the LS1 fit farther back, which lines up the shifter nicely, too.
After seeing this second test fit's engine placement, we were happier and now know which oil pan should work perfectly. We've also got a good idea on how we want to build the new front crossmember, which will be a custom tubular design utilizing mostly stock suspension geometry. Definitely some weight to be lost there. The rear differential was also mocked up with an
aluminum Ford 8.8" 31-spline differential carrier from a 2003-04 Cobra. This will need another custom subframe to mount this diff carrier, plus some other parts we will discuss later.
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