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MG MGB Technical - 79 MGB motor mount shims
|Are the motor mount shims on a 79 MGB slotted at the bolt holes or are they closed end??|
In short, do I need to remove the bolts from the mount ears to remove or add shims or can the bolts be loosened and the shims can twist in/out?
|Gary, the holes are not slotted (on my '78 and '80 B's) and you have to remove the bolts.|
|Thanks, Brian. My engine sits too high resulting the air filter coming in contact with the bonnet.|
|The only factory spacer is on the engine side of the rubber mount, and that has two holes, not slots. The V8 WSM says it is on the right-hand side, but shows it on the left.|
If you have any on the chassis bracket side (as is common on V8s including mine to keep the exhaust manifolds off the inner wing and steering column) they will be a PO addition and may or may not have slots - mine have slots, as it happens.
|Thanx Paul. I noticed the bolt heads are "topside" and one of them is pretty much up against the engine block. So it seems this will be quite a puzzle to take apart. It appears the steering column passes through the bottom chassis bracket to which the motor mount is attached on the lower end and the top is up against the engine block.|
Short of removing the steering column which seems the steering rack must also go, then the column, then the entire mount,then remove the excess shims and then reverse procedure .
Does that sound about right??
|My V8 has the same arrangement on the chassis side of the mount, but obviously differs on the engine side.|
I have changed mounts on that with everything else in-situ, but it is a fiddle turning the nut under the chassis bracket half a turn at a time with an open-ended spanner turning it over for each half-flat. At least enough to get it started, than having removed the two bolts on the other side you can unscrew the mount from the nut. But it's not really worth the effort, as you then need to stick things together to position the location plate, washer and nut to screw the new one back in. As I've had to remove the rack to remove the exhaust manifold that side more times than I care to remember I would always remove the rack.
However on a pals 4-cylinder the nuts were seized onto the mount studs, and with the rack out (that shaft goes through the chassis bracket, not the column shaft) for the right-hand side we resorted to a rope on a ring-spanner, with me positioning the spanner for each partial turn and my pal hauling on the rope that ran under the car! The left-hand side was even worse, the rubber was twisting so that I couldn't move the spanner round. Eventually I drilled through the edge of the mount, its stud plate and the chassis bracket intending to put a thin bar through to hold the stud plate still, but in the event the drill snapped as it broke through and did the job.
Faced with the same thing again I decided I would chisel the rubber off the stud plate to get the engine out, then grind the stud plate to free the stud. From notes I made at the time I slackened two of the bolts that secure the mounting bracket to the engine front plate, but not the third which is covered by the mount. I don't have a note about the two bolts that attach the mount to the engine bracket, but can only assume that they can't be done with the engine fitted, only with it removed or at least raised as high as it will go.
Note the locating plate under the chassis bracket, which has an offset hole. This must go in the lower of the two possible position on the mount stud to ensure they are positioned low enough in the chassis bracket slots. However they must not be right at the bottom of the slots or that puts the rubber of the mount in shear. That's the job of the spacer plate, that and twisting the engine about its crankshaft axis should result in both studs being just clear of the bottom of the chassis bracket slots, so the rubber is in compression. I also oiled the faces and tapped the stud plate down the face of the chassis brackets slightly, to ensure it was in compression, but still leave a gap at the bottom of the slots.
|Paul, While surveying the car with an exploded view of the motor mount shown in a Moss Motors catalog, there is really no friendly way to do this. There are two bolts that attach to the mount to the front plate of the engine. Removing those bolts still will not allow me to turn the mount enough to unbolt the shims and reset the mount .|
I've replaced these mounts and as you pointed out, you can only get at best a half turn on the nut (5/8" IIRC) The toughest part was getting the nut started on the bottom bolt especially on the drivers side.
In the end, I just may live with it as is.
Again, many thanks
Just a word which may save you the trouble. Because the chassis mount brackets are slotted , the engine can twist and tip the engine. You can see this if it's bad, but a spirit level will show it. All that is required is to slacken the nuts and put a jack under the low side of the engine. It's a requirement on V8's as clearance is tight, but not seen a problem on 1800's.
|"on V8's as clearance is tight"|
So tight they cut holes for the tops of the carbs and the filler plug in the bonnet insulation, and that was after having to change the curvature of the bonnet itself :o)
Like Allan, I've not heard of a problem with the 4-cylinder before.
This thread was discussed between 14/10/2016 and 17/10/2016
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