Doing a Rotary swap and the car im doing it on (fiat 124) its gonna be hard to get the engine to fit the way I want it with rubber engine mounts in between so I'm just trying to ask what its like from anyone whos done it before. Now I do plan to make it street legal and drive it every now and then on the street and on the track. I have pretty low standards for comfort, but how bad is it? I think it won't be that bad because rotaries are very balanced but, learn me
I have done solid mounts, with a rotary!
The short answer is NO, don't do it. Even with a rotary.
The long answer is, I too had a difficult time with engine mounting due to the subframe swap that I did on my RX-7, which precluded the use of the front cover mounting to the subframe, so I extended the front cover mount bracket to go all the way to the chassis rails, and hard-mounted that to the body.
Then I drove it, and it sucked, and that lasted about 12 hours, which was how long it took for me to get back into the shop and engineer a different engine mounting arrangement. Then I noticed that the new engine had NO OIL PRESSURE. I pulled the stationary gears out and saw that they'd been utterly destroyed. Also noticed that the oil passage O-ring in the front cover was missing.
Knurled Theory: Hard mounting the engine via the front cover caused the cover to warp enough under load to dislodge the O-ring, causing a fatal loss of oil volume/pressure to the bearings.
I am in the process of building my third track only car with solid mounts. I have never had an issue, but I am not really thinking about personal comfort when I am racing.
More anecdotes which may add up to data: In a previous life I played with a lot of Buick V6s. The ones that had hard engine mounts always had massive oil leak problems at the oil pan. The ones with normal mounts and a torque strap, or engine plates (engine mounts off of a plate between the engine and transmission), did not have oil pan leakage issues. Torque and vibration against the factory mounting points with solid mounts would warp the block enough to make the oil pan gasket region lose its seal.
Wonder what it was doing to the main journals. Or, for that matter, the cylinders.
A compromise is to put one solid mount on the side of the engine that it rotates toward (usually the passenger side), and rubber mount the other side. Theory is the solid takes the abuse, but the rubber side allows movement.
In reply to Appleseed :
I always use the solid mount on the driver's side, and the rubber mount on the passenger side. The driver's side mount is the one that sees the abuse.
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