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          Thinking that just because your favorite parts supplier lists a rubber thingy and a square metal box with two holes in that you're good to go as far as the front engine mount on your 235 engine?? Well if you are, then you are oh so wrong -- there's actually two additional pieces! Don't panic, though -- you have plenty of company (the Editor is in that boat with you ). To help sort this mess out, here's our old friend Don to help you sort out the ....

Front Motor Mount for the 235 Engine
By Don "down2sea" McLendon
1941 Chevy 1/2-Ton Pickup Truck
  January 2009
The complete 235 front motor mount is comprised of four parts, listed at left. Clearances are critical so make sure you have your micrometer handy! << click on image for larger view >>

First things first!

Before we even get started, we'd better settle the issue of just what, exactly, comprises the front motor mount on the 235 engines (most of the pre-Sixties straight sixes, actually).

Something to keep in mind is that the vendors don't have the complete nomenclature.

Here's the skinny from the 1929 - 1957 Master Parts & Accessories Catalog: (Thanks to Keith Hardy )

Complete Front Mounting Assembly Breakdown (top to bottom)

Part # Nomenclature Dimensions
3656502 Shield, Frt Mtg 7 15/16 x 2 1/2 wide
3657522 Plate, Frt Mtg, Top 7 7/16 x 2 wide
3657520 Mounting, Engine Front  
368449 Retainer, Frt Mtg 7 7/16 x 1 5/8 wide

Here are the pieces. If you want to see all the pieces, I have front motor mount assembly photos here on my Picasa photo hosting site. These should come in handy for anyone wanting to fabricate their own. The clearance between the retainer and the plate is critical and is described in this section of the 1948 - 1951 Chevy Truck Shop Manual. The clearance should be between 3/64" and 5/64" unloaded with mount installed. If the clearance is less than 3/64" the retainer should be filed or machined. If the clearance is more than 5/64" the retainer requires replacement.

Just what DO the vendors carry?

Jim Carter -- ME533 Motor Mount Shield (3656502 Shield). They do not carry the plate or retainer

Obsolete Chevrolet -- ME533 Motor Mount Grease Shield 6 CYL FITS ABOVE ME216 actually the (3657522 Plate). There is some confusion in part numbers but it appears that Obsolete Chevy carries everything but the retainer. Call them to sort it out.

American Classic -- MM-12 Motor Mount Front Shield. They do not carry the plate or retainer. Their MM-12 is only about 8 bucks, but they have a $20 minimum order which is the only vendor that has this restriction to my knowledge.

Why no vendor carries the complete assembly or doesn't use the proper nomenclature is beyond me.
Also, because of the close tolerances between the retainer and the plate, I don't understand why none of the vendors stock the retainer. Hopefully, you still have your original or can find a used one -- good hunting!

As best as I can determine, the two carriage bolts used for the engine bracket / plate / mount / retainer / frame segment are 7/16-14 X 2 (Steel Grade 5) and can be found at Bolt The shield / frame segment bolts are 3/8-16 X 2 and not required to be grade 5.

Putting it all together

Thanks to Dave Razey [ 1954 Chevy 5-window Shortbox ] for his help with this part!

Now that there is a clear picture of all the components for the front mount, let me offer a bit of advice that is gleaned from the shop manual and from my practical experience(s).

The Rubber Mount

I replaced my soggy original with a rubber repo from one of the major suppliers. It's a drop-in, but wait a minute .... you'd better make sure that you get it oriented properly (slots up) and the required clearances between the bottom housing and the top plate. If you assume that a new rubber insert will bring the clearances back up to snuff, you may be in for some nasty vibrations that won't be evident until you get everything installed and the engine cranked up!!! I found the clamping the assembly in the vise ... to simulate the weight of the 620+ pound engine ... left me with little or no required clearance. The lower "box" had to be dressed down. Evidently, the repo rubber insert was not quite as thick as the original.

The Harmonic Balancer

Secondly, the assembly needs to be installed before you install your harmonic balancer (Editor's note: Now you tell me...). The thru-bolts that hold the rubber and top plate and float in the cross member holes should be loosely assembled. The carriage style bolts that actually fasten the mount to the crossmember can then be guided into the holes. You will probably need to move the entire assembly around to get everything lined up. Then drop the full weight of the engine on the mount and tighten the bolts. Check to make sure the 7/16" thru-bolts are centered in the large opening in the cross member. If they aren't, and they make contact with the edge of the hole, you'll get vibrations. These thru-bolts are tightened down tight as they are insulated from the cross member on the molded metal insert that floats in the large cross member hole!!! The two outer carriage-type bolts that go through the cross member are just snugged down and the cotter keys are installed. The rear mount bolts should be loose when installing the front mount.

Now it's finally time to install the balancer. Drilling and tapping the crank to take a SBC bolt makes it easy to install the balancer. However, you want to use a threaded stud, a couple big greased heavy washers and a nut to draw the balancer on. Trying to use the SBC bolt to draw it on will put undo stress on the fine threads on the crank.

Last Thoughts

If you get in a bit of a rush and don't make sure you've got the proper clearances, the bolts installed properly and the assembly aligned correctly -- you're going to have nasty vibration issues. Getting it right the first time will keep you from having to put your fingers under an engine that's jacked up with a floor jack .... no way to block it up safely .... and work blind (by feel) to loosen and tighten the thru-bolts.

Hopefully we can save someone else from frustration!
(Editor's note: Too late!)


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