[tutorial] Rigid Mod: Stiffening engine subframe (+ engine mounts)

Hello Guys

decided to make a quick tutorial about stiffering the whole drive unit in our K11.

I did everything with one job with front crossmember, so heres a list:

1. New front crossmember
2. new engine and gearbox mount
3. glued mounts
4. rigid collar at rear subframe bolts (rigid mod)


okay, as said I've fighting with crossmember, during work I found broken subframe bolts cushions... I can guess why this joint aren't rigid ('cause vibrations) but imo using rigid joint at one end and cushion type at another is quite stupid...

1. anyway, replacing the crossmember (if its rusty) is main thing. I was surprised how the rusty old one holded at place, the back wall is pretty fat, so if yours isn't rusty full-aroud it can hold the engine in place. But you'll fail mot anyway so replacing is mandatory...


2. all mine engine mounts were broken, Wanted to replace all four, but found only left one (engine) and rear one (eng/grbx) at local shop. These were quite expensive ,so decided to use old trick with window weld (glue)

3. I reccomend to use primer for this window glue, because in mine case, the glue didn't catch the sufrace well, BUT holds at place were cushion bends ,so I'll chceck how it will preform and glue it again if needed.

SAM_3665.JPG

SAM_3694.JPG

glued all 4 mounts, two new and two old ones.

Glue the front one (this one closer to radiator) well, looks like it's responsible for accel/decel slack (big thanks to Pollyp)

https://www.youtube.com/watch?v=U_aAdWTywoM
4. Main thing- stiffering this damn subframe. I think they wanted to isolate the vibrations from subframe to body... but theres two damn rubber mounts. Can't understand this but eh...

okay I choose simplest way (it meant to be only for testing but I bet it will stay forever :D

all you need:

-two full-thread 1.25 bolts
-two spacers matched to holes in subframe
-two (or more) spacers wich were holding the subframe during Hard Charging :p It is safety thing- I've used just two, but maybe I'll add another two.

I think everything is quite clear at photos. The smaller spacer must be tight matched to subframe and the bolt. Also it should be as thick as subframe.

the bigger spacer should be as big as possible.

SAM_3692.JPG

(note: I was thinking about welding smaller spacers to subframe, but I'll make it if will preform good)


Okay, thats all, I've tested it a bit only, near the garage, because whole front-end is removed. I was surprised- no rattling at all and huge increase in response. Rustbucket was losing traction during accel. at gravel instatly. Body vibrations at the same level as with broken subframe bolts cushions or even weaker
(note: engine was cold so didn't drop at the idle speed. Will report this it after tests).

SAM_3682.JPG
will report more after some solid test drive.

expected cons:
-may transfer engine shakes/vibration at whole body
-may transfer some not expected forces at drivetrain/body? (theoretically)
-work is quite time consuming
-bolts in older cars can be rusty as hell

expected pros:
+ increase of drive unit rigidy, response and overall accel/decel feeling for driver
+ if cushions were broken mod can help retrieve "missing horses" lost due engine movements
+ not so expensive

okay, thats all, maybe it will be helpful for someone in future.

cheers
Matiz
 
OP
OP
Matiz
Hello

okay, mods preforms well. As expected- car reacts better during accel and decel, theres no "slack" and rattling. Compared to driving with broken subframe cushions its much better. Theres still some kangaro hops during engine braking (dunno how to translate) but eh- theres 222 222km at the clock. Rustbucket :p

about glue- you have to use primer, in mine case glue were pushed out from mounts cushion, but still holds in one piece and still stiffering something....

last thing about vibrations- theres no difference, still shaking at the idle. Looks like engine really running rich, ot its caused by Rigid Mod. But I dont mind.

its Rustbucket.

Cheers
Matiz
 
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