Breaking bell housings

[Mike Jones]

I broke the bell in my 12 second bracket car, 355/ TH-350 Camaro.
It had factory urethane mounts on the front crossmember and steel mounts bolted to the block, like they came in 1979
The driver side motor mount was slightly bent and the engine was
cocked up on the drivers side, just a bit. Could hardly tell, if you weren`t looking for it.
Found the bent mount when I pulled the motor.
Had rubber trans mount as well
Check the motor mounts are the same and not bent.
Just a thought...
Good luck.

[Alan Roehrich]

If this car has the stock suspension, un-altered, other than urethane bushings, and the rear end housing has not been changed, damaged, or otherwise altered, if the frame is not bent or broken, then the pinion angle should be close to stock. Unless the ride height is significantly altered from stock.

Now, if it has traction bars, no hop bars, adjustable control arms, the housing has been swapped or altered, or the ride height has changed significantly, then the pinion angle could be off.

If the pinion angle was off enough to break something, there should be a vibration present. Of course, solid motor mounts bring about a vibration of their own, and that could mask any vibration brought about by another cause. <------- Another reason that I despise solid motor mounts.

If the dowel pins do not protrude into the case far enough that the chamfer on the pins is well past the chamfer on the case, so that the full diameter of the dowel pins is well into the holes in the case, that could cause the problem.

At static ride height, the slip yoke should be about 1" out from being fully bottomed in the extension housing.

I think the first thing I'd do is verify that there are no problems with the rear suspension or rear end housing, and that the driveshaft is correct, in length and in tubing diameter and thickness, as well as having good u-joints. After that, I'd put the mounts back to the stock configuration, either new high quality rubber mounts, or new urethane mounts, on the engine and transmission. If you want, you can fabricate a torque limiter of some sort. I'm betting at that point your case breakage problems will cease.

[SStockDart]

All of these suggestions sound logical to me.....let me just throw something else out there, in case these suggestions don't fix the problem. I have seen where the back of the blocks were crooked, therefore requiring shims to be sure the bell housing aligns "straight"..
"back in the day", it was common to break 4 speed transmission housings......after dial indicator and shims, I never broke another. Good Luck

[FED 387]

big difference between 8000 RPM and your boulevard cruiser at 1500-2500 RPM MAX--do a dial indicator first see what you come up with then go from there--- those mounts probably are aggravating the situation too-- my 2 cents

[jbt352]

Thanks for all the ideas.
I like the idea of going back to the factory front mounts,considering the power level we are talking.

[Signman]

Great thread!
The reasoning for not using solid engine mounts to avoid this problem may be a good bandaid for the real problem: Chassis Flex.

When building my cars spent a lot of time making the floor pan stiff welding all seams top and bottom with the car level then locating roll bar mounts with chassis stiffness the intent within the rules. A lot of hard dirty work but makes stock chassis cars stiff and lets the suspension work.
Rubber body mounts on A and G bodies replaced with solid steel or aluminum helps a lot.
Even though this is a 13 second car doesn't mean there is no flex. Get rid of it and pick up some ET.

Good Luck!

[HandOverFist]

Been running street/bracket cars for years with solid motor mounts and rubber trans mounts at various power levels...never cracked a housing yet. We must just be lucky.

[Ed Wright]

About the solid side motor mounts:
If you run a production block (Bow Tie blocks didn't exist when I was showed this.)
Bare block, with something soft below the test cylinder, put an inside mic in the cylinder above the soft pad, front-to-rear, up top, barely tight enough to stay in place. A healthy guy with hand above & below the mic, press hard & fast together and watch the mic fall to the pad. The old guy-machinist that showed me this about 50 years ago was no body builder either.
Think about your ring seal during launch in the cylinders next to those solid motor mounts. I would use a torque strap with stock mounts myself.

[MAURICE BLENDHEIM]

jbt352… Mount the body solid to chassis by welding flat bar between frame and body mount reinforcement pads (helps reduce chassis flex). Check to see if your rear upper and lower control arm bushings are in good shape, worn bushings can change pinion angle on acceleration. I'd add a aluminum convertor cover off a mid 80's GM 4x4 to act as a case girdle in the bell housing area. You have lots of positive feedback from your post. Good Luck…Maurice.

[Dave Gantz]

Originally Posted by Ed Wright

About the solid side motor mounts:
If you run a production block (Bow Tie blocks didn't exist when I was showed this.)
Bare block, with something soft below the test cylinder, put an inside mic in the cylinder above the soft pad, front-to-rear, up top, barely tight enough to stay in place. A healthy guy with hand above & below the mic, press hard & fast together and watch the mic fall to the pad. The old guy-machinist that showed me this about 50 years ago was no body builder either.
Think about your ring seal during launch in the cylinders next to those solid motor mounts. I would use a torque strap with stock mounts myself.

I remember reading years ago that Bob Glidden built engines on the floor so that the cylinder walls would'nt distort. That made me think some, and that usually hurts!