This evening I lowered the engine. The intake now sits about 7/16ths of an inch (about 1 cm) above the support bar. Looks like the total lift from where it was sitting on the short-lived anchor mounts is about 3/4 inch (almost 2 cm).





I immediately noticed the air intake tubes set down on the cam gear/timing belt cover cooling ports very positively (where before I could barely get the tubes to stay on the ports).

I don't see any immediate clearance concerns. A hex screw on the right fuel rail cover is directly beneath the support bar and close to touching. I'm wondering if it will vibrate against the bar during start up or when mashing the gas.




The MM fingers on the left are about 1 mm apart, and 2 mm on the right. Has experience shown this to be normal? Will a few hundred miles of initial break in cause enough settling to separate the fingers a bit more?




Thanks. The MM/OPG has felt like a rite of passage. I highly recommend it

 

I'd think that the hex nut should be a safe distance, considering the amount of travel allowed by the left engine mount. You said it measured 1mm at the engine mount hook, and when you take into consideration the mount is located farther out on the width/plan of the engine, and with the hex nut being closer to the axis of the engine...the range of movement should be less than 1mm.

Hence, anything located closer to the axis of the engine will travel a shorter distance when accelerating/revving the engine.

And yes...you are worthy of owning a Porsche after that job. Two thumbs up!

Brian.

 

as the mounts go through a few heat cycles the clearances should increase.
HOWEVER you can make a few adjustments to the finger pads.

This is best done with the car supported securely on 4 jack stands,
to do this requires a floor jack and a helper ,
a 1/2 inch drive extension with a 17 MM socket,
the extension should be 6 inches long.
put the socket on the extension the place the jack under the finger that you want to adjust,
the socket goes onto the bolt head,
have the helper slowly raise the jack.
the jack will push the socket upwards and thus the finger will bend slightly .

NOTE you dont need much jacking to effect a change only about 1/2 an inch , or less
go in small increments.

 

On my S4, the new factory mounts had the engine about 1/2" lower than your pictures show, and that was after a week of settling in. I don't normally expect motor mounts to "settle in" much if any, but need to qualify my results with that JIC.

The only 'interference" I found with new stock mounts is some crowding on the passenger side air tube at the top of the cam belt cover. With the aftermarket mounts installed on other cars in my workbay, that clearance was slightly less. However, none of the aftermarket mount installations were on S4+ cars so no definitive intake measurements from those would apply here.

For the safety hooks, all were touching or tighter (read: negative clearance), and needed some adjusting (read: bending) to make sure there was at least a little clearance. It only takes a little bit of clearance, unlike most 'murican cars with open driveshaft. What's the difference? The torque tube in the 928 eliminates torque twisting of the engine relative to the rear axle under load. The remaining engine and transmission movement is solely the reactive twisting as the rotating bits are accelerated or decelerated relative to the block and transmission housing.

 

Ahhh...I'd forgotten about the benefit of the torque tube design is elimination of driveline twisting. Well, I'm waiting on Delrin bushings and new upper ball joint boots. After I'm done with those I drive it and see what happens. If I don't hear any contact noises I won't make any adjustments. I'm heading out to reattach the starter and sway bar. I'll take a more careful look around the sides and rear of the engine. Also will release the P-Klamp and stock flex plate clamp and reset them.

 

The new Delrin rack bushings arrived yesterday and today I installed them and put the rack back in, and the starter, etc. Ran the engine with car on stands to check for leaks, and again with the wheels on the ground. Each time I let it warm up to the point where the fans came on, then revved the engine to see how much more it rocks with the new mounts. I was pleased to see that the mounts did settle approx. an additional 2 mm.

 

Nice job Jon - check that your oil filler neck is not rubbing a hole into the front fuel hose. You may want to add a sacrificial piece of hose/sleeve around the original at the wear point.

 

Thanks Roger...I did notice a bit of wear on that hose and forgot to put a hose sleeve on it.

 

A few more pics. This is a big job, but not technically challenging. It's been like going to the gym every day

I actually installed the OPG twice. First try I attached it to the crankcase flange...bad idea. The gasket drooped into the pan as I raised the pan into position. I fouled the gasket with drips of oil from above. So...two days later I completely removed the pan and gasket again and attached gasket to pan as shown below. This worked PERFECTLY...I was easily able to slowly lift the pan up and over the hanging steering rack and set the gasket/pan perfectly against a dry clean crankcase flange. So far, after running the engine a few times to get the oil hot there are no leaks.



View of the bottom when finished. Note the white Delrin steering rack bushings. I pressed these in using vaseline and a large C-clamp.

 

Isn't that a wonderful sight?

 

You betcha! Right after I took that picture, this happened....

 

I think you deserve it!! Congratulations.!

 

Looks like I'll have to adjust the gap between the motor mount safety hooks/fingers. Took the car out for it's first drive. At rest, in park, revving the engine is very smooth. The engine rocks gently.

However, driving is different. As long as I drive it gently (normal driving) it is fine...very smooth. But as I coasted through a curved on ramp and then started accelerate hard I got a vibration from the front and could feel it in the steering wheel. Backing off the gas and accelerating gently removed the vibration. At constant highway speed there is no vibration. Then when exiting the highway, again coasting through a curved on ramp, I started to accelerate moderately to exit the ramp and merge on to the next road...and again the vibration returned. Again, returned to constant speed or gentle acceleration does not cause it.

I experimented a bit. Accelerating moderately while going through a curve creates more vibration than the same acceleration in a straight line (though still present).

Does this sound like finger hooks touching?

 

yes your hooks are touching,
if you follow the suggestion I made to use a jack and socket and extension,
it will make the needed clearance.
NOTE you dont need to jack more than a 1/2 inch once the socket contacts the bolt head

 

I followed Stan's instructions for increasing the vertical gap between the finger pad and the hook. It worked perfectly. However, the vibration persists, and I think I know why. The right (passenger) upper finger is sitting about 2 mm from the hook in the horizontal, while the vertical space is now about 5 mm or more. I tried to pry additional horizontal space, but I think the solution is moving the passenger side finger pad toward the front of the car. I would like to avoid using the engine support bar. It would be great if I could drop the steering rack, loosen the lower motor mount bolt, jack up the engine slightly on the passenger side "ear" enough to unload the finger pad enough to pry it forward a few mm away from the hook.

The vibration only occurs in two situations. There's very slight vibration (someone not familiar with these cars may not notice) when accelerating hard in a straight line. There's more vibration when making a sweeping turn to the right and accelerating hard. Oddly, there is no vibration when turning sharply right or left (round and round in a cul de sac as if on a skid pad).

It seems to either be an inertial effect or due to a momentary twisting of the unibody. Must be accelerating to make it happen, and the direction of the acceleration must be a vector from the driver through the passenger headlight (sweeping right turn). Whatever the mechanics, the finger pad and hook touch horizontally.

I should mention that both right and left fingers/hooks have similar and ample vertical gaps after applying mrmerlin's technique. However, the left side (driver's) has about 4 mm fore/aft horizontal clearance between the vertical section of the J hook and the upper finger, while the right side has about 2 mm.

I can't think of any other cause for this vibration. At idle or with gradual acceleration straight ahead or making left turns the engine is smoother than before I put the mounts in.

Any ideas?