TDI install retrospective: Physical Mounting

Continuing the process of back-documenting what I did to put a TDI engine into an old (1972) air-cooled VW bus. Today I cover physically attaching the engine to the bus. This may sound simple, and if you only saw the end result, you might still think so. That's the beauty of what Hal built. Elegant in it's simplicity.

Transaxle Mounts

early mount attempts

The stock bus has three mount locations for the engine/transaxle combo: the front of the transaxle, the bell-housing in the middle and the "mustache bar" near the rear. I decided to reuse the transaxle mounts without modification. The transaxle wasn't really getting modified, so it should just fit. And it did. There were some who questioned the vibration through the mounts at the bell-housing, though. I believe there have been experiments by others where the bell-housing mount was eliminated, but I have also heard that this put stress on the output shaft and other components because all of the weight was being handled on the ends. Looking at the front-most transaxle mount, I'm not sure it really should hold up more weight than it was originally designed to hold. Your bus; your choice. Now, years later, I am fairly convinced that the bell-housing mount holds most of the weight of both the transaxle and the engine.

Motor Mount Attempts

bar to rear frame, 1st model

I looked at and tried a few different things to mount the engine. First, we tried building mounts that would attach to the sides of the engine to threaded bolt holes that were unused in the stock vehicle install. These bolt holes were on the block for industrial applications of the engine so, they should have been stout enough to do the deed. The idea was to reuse the original bolt holes for the mustache bar. The holes in the block and the mustache bar didn't line up very well and since the plan didn't include anything to absorb vibration, the bus would have shook like a paint mixer. I tried to accommodate this issue with some vulcanized rubber mounts, but it looked complicated and not terribly strong. So, I threw the whole thing out, and got to talking with Hal about it.

box being developed

Hal knows bus. He recognized that the rear bumper brackets are held to the bus with thick carriage bolts to the rear frame. The same rear frame that the mustache bar attached to, just more rearward. We figured that if we leveraged the mustache bar concept with a thick, straight bar between the bumper brackets, we could re-use the stock TDI passenger-side motor mount. To the right, here, you can see an earlier version. Hal and I agreed that something less complex would work.

Motor Mounts
Seeking something simple, we started with a piece of 1" angle-iron, onto which we marked and drilled holes to align with the bumper bracket holes. The bracket was then bolted to the rear frame so a straight bar could be measured, cut and welded on. Bar done.

Then, Hal welded together a simple box with a central support that would join the mount to the straight bar with bolts. The whole thing bolts together: the bar to the frame (re-using the bumper bracket bolts), the bar to the box (with a basic bolt-nut pair) and the box to the mount (again with a basic bolt-nut pair).

I have removed and re-installed the engine both with and without the transmission numerous times. This part of the system is a total non-factor in the process. I have also removed the rear bumper a few times independently of the motor mount, and while it is slightly more difficult than before, it is not really impacted: I simply support the bar with a floor jack, remove the 4 bolts (2 per side), remove the bumper, put the bolts back in and lower away the jack. Super simple. Of the things that were done for me for this build, this is the single greatest contribution. I said it then, but haven't said it enough since: THANK YOU, Hal. You really crushed it.

Measurements of the straight / cross bar:
length of main span, from bracket to bracket: 42"
angle-iron "bracket" depth (front-to-rear): 6"

Measurements of the box:
across the top: 9"
height: 7.75"
space between vertical bars: 3"

Prior related posts:
Preparation
Fuel System

Next related posts:
Vacuum System
Air, Intercooler and Exhaust
Primary Electrical
Cooling
Secondary Electrical
ECU, dashpod and Sensors