912 to 930 Conversion

[wkrtsm]

My planned torque is much greater than OEM with HP~500. Lots of work: welding reinforcements on rear/front shock mounts, welding in RS/SC-type support for torsion tube, elephant ERX-930 brakes, 23mm master cylinder, wheel upgrade 9x17 front/11x17 rear, welded in fender flares, composite 930 front/rear bumpers, shifter/linkage upgrade, gauge upgrade, etc.

While I did see the post on 915 to 930 transaxle upgrades and what works/doesn't work from 915 leftovers, I have the following questions on 930 transaxle dependencies on rear suspension:

1). Trailing arms: Would it be better to upgrade to Carrera trailing arms, or simply install later 912/911 (1969-71) LWB trailing arms - and build from there? For Carrera arms, I'd have to weld new pivot points on the torsion tube.

2). Torsion tube: aside from welding in RS/SC-type support metal (as in Torsion tube failure - and repair - the project ), do I need to do anything else besides weld pivot points on for Carrera arms?

3). Rear torsion bars: A heavier would likely require ~26mm rear torsion bars, but coil overs are also necessary. Anything else?

4). Spring plates: can I mix and match LWB 911 spring plates with Carrera arms, or would I need Carrera spring plates?

5). Shafts: 901 CV shafts are too weak (understatement) and may not fit. What's recommended fitment?

6). Half-shafts: I saw on a post that G50 axles are the go-to for 930 transaxle upgrades from 915. What's best for Carrera arms?

7). Axles: are the current axles in a '68 912 strong enough for more torque?

8) Flywheel, pressure plate, clutch assembly, throwout bearing: It's been pointed out that one needs to be careful on clutch disc selection, since the wrong choice can results in leg fatigue(?)


(930 transaxle fitment in a 912 chassis is a different topic altogether, which has its own labor/complexity issues).

[jess p]

I did a similar mod in installing a V8 in a swb 912, I regretted it. First, I cut out the torsion tube and welded in a 911 torsion tube. From this I installed carrera aluminum trailing arms. Keep in mind when you make this car a lwb car you will see that you now have to modify the shock mounts in the body. When you weld on the rear turbo flares front and rear you will see the tires are not centered because the rear tires are now further back. You will now have inherited a truckload of headaches. You will not be able to install a 930 transaxle into a 912 swb car because of the torsion tube design.
I don’t mean to rain on your dream but you are better off finding a roller 911 mid 70’s for this project. I’ve only included a small portion of headaches you are going to encounter.

[wkrtsm]

The rear flares would be fitted after the LWB mod. Why would you weld flares on during SWB, and then go to LWB, which moves the rear axles back about 2"?

[jess p]

I welded them on after the torsion tube mod. It still didn’t matter. But, I gave you my 2 cents worth, it’s your car