Saner swap thoughts
 

Ok, I've had some less insane, more realistic swap thoughts kicking around, lemme know what y'all think...

Miata 3rd member... Apparently '94-up Miata 3rd members are a direct swap into '84-85 rearends if you cut the power plant frame mount off. My thinking is... WHY? Why not design a torque arm that bolts to the PPF mount? If it interferes with the Watts linkage, then convert it to a Panhard rod setup, that seems to be what people do when converting from a 4-link to a torque arm setup anyway. I don't think it would be race-legal but it would be a killer idea for cars "not subject to rules". I mean... the mount is already there, and it's designed to handle heavy driveline loads.

(Instead of separate diff front mounts and transmission mounts, cars with a PPF have this big ladder-looking member that bolts the end of the transmission to the differential, so they support each other. That's why FDs mount the engine at the rear housing)

I noted a while ago that one of the "past project" engines in the Racing Beat catalog (the '76 dual 36DCD engine) appeared to have a Chevrolet bellhousing/scattershield adapted to it. Just one problem... where do you put the starter? I think I figured it out... have the starter drive a toothed belt that goes to a pulley on the front of the engine, possibly/probably where the a/c compressor sits now. No guesses on reliability, though, but at least with a toothed belt it won't require high tension like a V-belt that could distort the E-shaft. The starter idea is just a supporting idea, though, for the thought of adapting a Chevy or other bellhousing to the rotary, which would open the doors to SCADS of different transmissions! T10s... Muncies... T5s... T56s... any and all of which (well, maybe except the T5 and T56) were designed to live behind stupid-high amounts of torque and put up with powershift after powershift. NASCAR guys still use T10s and there is a large aftermarket for T10s and clones, which is why I gravitate towards 'em.

Uh... more later. :)

Hopefully not too much later!

How's this for saner swaps:

My friend installed a '93 13BREW in his GSL-SE and used the stock rear housing mounts of the engine on a modified U beam of stock steel (you know, like angle iron and stuff). The mods to the beam allowed it to be angled slightly like an upside down arch (like a smile) under the engine and bolted to the unibody near the steering box/idler arm bolts.

I now know this will not be enough thanks to peejay's post.

Since my friend had all this work done, he has decided to change his plans and remove all the '93 turbo stuff in favor of an Atkins supercharger kit. It'll still be around 255HP I suppose (Dave Atkins figured it would have basicaly stock HP, go figure). And he will either need to get an '86 or later front cover, or go with the good old '74-'85 style. Yes, the stock front cross meber has been removed. I'm not sure how safe this is. Will the front end strength suffer because of this?

I'm only mentioning this because I noticed that the engine jiggled very easily. I asked my friend why, and he said it's because the mounts are gel filled. Uh... ok. My friend isn't a detail kind of guy. Neither is the shop he had the work done at.

My main concern here is the fact that the car's stock GSL-SE tranny and mount are to be used with the stock 13BREW engine mounts. But there is no power plant frame!! No wonder the engine jiggled at the slightest movement. Those so called gel filled mounts are just for vibration dampening. The PPF is supposed to handle the torque load right? That rear GSL-SE rubber tranny mount doesn't stand a chance!

(my bro's GSL-SE tranny mount was broken with a stock engine!)

So what's the worst that could happen? All the rubber in the mounts will stretch and break. The exhaust header will twist and crack very quickly. The engine will torque itself around and snap the shifter right off the tranny. Or worse.

Any thoughts?

Hmmm, I'm seeing all 3 mounting points break and the motor resting happily (or not) on the ground under the car. I'd definatly get a 1st gen front cover and use the front mount and try to fab it so that the rear mounts can work with that, since you want as many mounting points to the chassis as you can get w/ a setup like this.

I'd be really gentle driving it until then, since the engine/tranny falling out after launching off a light would SUCK.

--matt

Jeff20B... YUCK! Although I do enjoy a good hack-job... :D

What I meant by torque loads was at the rear differential, where the pinion tries to violently torque upwards. Instead of having a complex and heavy array of mounts that can transmit vibration to the chassis yet still be sloppy, Mazda (rather brilliantly IMO) just made a big beam that bolted it to the transmission. That's all it does... it holds the differential in place to keep it from rotating up or down. The engine mounts still handle the engine's torque loads, and they probably ARE hydraulic, as hydro/liquid/"gel" mounts are quite common on modern cars.

Our 1st-gen engine/trans mounts are like holding a board up on two sawhorses. The 3rd gens hold it in the middle with just one, and the PPF keeps it from flopping over. If the engine half is heavier than the trans half (which might be the case with your friend's setup) then his trans mount might not be holding the transmission UP like it was designed to do, but rather holding it DOWN. Still sounds like a cool hack, though! (Ehh, if the trans mount fails just hold the tranny down with a ratchet strap around the crossmember, yeah that's it!)

Now what would be REALLY cool... :D going further on my torque arm ideas, why not just ditch the stock rearend altogether and use a 3rd- or 4th-gen Camabird rearend, they already have torque arms and are close to the right width, and they're strong enough for 11's or so for a 3600lb car. Along with the Camaro T5/T56 (prolly T5) transmission, which has the torque arm's front mount attached to it. Shorten the torque arm to suit (won't be much... similar wheelbases and similar engine placement relative to wheelbase) and have the driveshaft shortened. Perfect.