Guys,

I need to raise the motor slightly - 1/8 to 1/4 inch to get the pan off my rack. I have the Canton RR pan and it's pretty much sitting on my rack and I'm afraid it's going to damage it over time, plus it's translating a lot of vibration into the body from the motor. I know this is a common thing with the Canton pan and they recc to shim the motor mounts or lower the rack. Has anyone ever used shims on the motor mounts to raise the motor slightly? I want to know the best way to do this as it doesn't seem to me if this will work as it will throw the angle off and cause the mounts to not line up. Any help is greatly appreciated.

BTW - My motor mounts are Poly and only have about 500 miles on them, so I know that's not my issue.

 

I never shimmed them but am wondering if this changes the pinion angle?

 

Yeah there is a maximum angle for the drive line, but you shouldn't need that much to get clearance. I think if you get high quality U-joints to eliminate any possible new vibrations you should be good.

 

Driveline angle has to do with much more than vibration. In fact, you won't get any vibration if you fall well outside the specs on pinion angle.

As little a 1/2 degree of pinion angle can affect how a car 'bites' on launch as well as how the chassis reacts. Wheel hop can often be tuned out with proper attention to that angle and the quality of the suspension components.

Since our cars are made on a production line with tolerance around everything, you can't know where in the specification a particular car is without measurement.

Probably the best way to handle this issue is to relocate the staeering rack and add a bumpsteer kit to fix the steering geometry that allows the car to self steer over bumps. It's actually worthwhile on stock cars as the geometery isn't perfect to begin with.

 

Thanks and I'm not too worried about angle of the driveline or pinion angle as I have an adjustable TQ arm and can change that if needed. I'm more concerned about raising the motor ever so slightly to clear the rack and I'm sure someone on here has used shims on the mounts before?

 

Oh yeah as hunter points out wheel hop and bite etc, that certainly could affect that. However since shimming is easy to do and is recommened by the manufacturer, and removing it is also easy then why not try it first.

I've done motor swaps before where the power train being mounted was not originally available in the car, so I have shimmed them before, but this question is different apparently.

 

It wasn't recommended by GM.......LOL

Of course shimming would work for the oil pan manufacturer. All they want is the thing to not touch anywhere. I think it's a bad idea and wouldn't do it but that's me....

 

Thanks everyone for your help and inputs, and I thought I'd follow this up as it seems most threads I search these days have no conclusion so it's hard to get an idea of how things worked out.

We installed the new prothane black mount inserts this past weekend along with the Moroso mount shims. I ordered this kit:

Moroso (62535) as it has various thickness plates and are made for the SBC 3 bolt pattern on our blocks.

Moroso 62535 Motor Mount Shim Kit : Amazon.com : Automotive

Ended up having to open the holes a bit with my drill press to get them to line up better and drill an additional hole for the bolt on the clamshell on the driver side holding in the Prothane mounts. After some considerable tweaking and lining up we finally got her all bolted back together using the 1/16in thick shims as the rest were just too thick and the mounts would not line up at all with the pin/bolts.

All said and done, the drive angle did not change and the vibration is gone as I now have about an 1/8 inch air gap between the pan and the rack. I did have to go to Ace and source some new motor mount (mount to block) bolts - grade 8 of course - to account for the thickness of the shim as I didn't want to use the stock bolts since they weren't biting too much into the block. Car runs beautifully and feels much better and no vibration from the driveline as well.

Thanks again!!!!