The Stovebolt Site Forums The Shop Area Engine Shop Forward motor mount clearance

Hey guys I have a question about the fwd motor mount clearance. I checked for the required clearance prior to putting the weight of the motor on the mount and my clearance was spot on right in the middle of requirements at 4 /64. After installing the engine it appears there is no clearance now just using the eyeball check. I plan to try to slide a feeler gage in there today to verify what my eyes are seeing. The mount is new and never used so when I saw the initial clearance I figured I was good to go. I hate to grind away on this and make the gap too large. Any suggestions?

Deegs

Deegs, Per the notes in this Legacy Tech Tip and the 1948-51 Shop manual reference doesn't indicate a measurement after the engine weight is dropped onto the mount. Only measured before it becomes "loaded". I would expect there is going to be a reduction in your clearance now that the engine weight is resting on the mount. If it measured correctly at the beginning, you should be just fine.

Dan,
Thanks for the sanity ck. I figured the clearance prior to the load meant they expected the gap to close when under a load. Did many pre load cks on F4/D/E act canopies, landing gear and flight controls but those are flying bricks so just a little different than my truck.

Deegs

Aerodynamically an F4 and a '53 3100 are not that different, but the F4 has more horsepower.

Out of curiosity I went out and looked at mine. When new and engine sitting on it, I think it had about .015" or maybe .020" clearance between the two metal pieces. After 7 or 8 years it has none. I've always thought a bit of clearance here helped dampen engine noise through the frame. For years mine used the 2 front side mounts (on top of rubber doughnut looking pieces) and the two rear mounts on the bell housing. It was notably quieter...especially at highway speeds. When I added A/C and used a different mounting scheme, I did away with those and used the old style front mount.

The mount is designed to not have any metal to metal contact loaded. The generous gap specified before a load in applied ensures that there will be no metal to metal contact once the load is applied.
There is one other thing which ensures no metal to metal contact when you are done. It involves the instructions for tightening the nuts which go through the crossmember.
Tighten them just snug. They are referred to as locking nuts. Overtightening them will cause metal to metal contact.
The original bolts have a holes for a cotter pins.
These pins do not lock the nut in place. All they do is keep you from losing the nut once the rubber gets oil soaked and collapses and the whole works bounces around causing the nut to want to come off.

Been thinking about this. I need to address my front mount sooner than later.

I’m sure replacing just the rubber is the simplest solution of all the various metals bits are in good condition. But if any are beat up or missing…..the factory style front mount seems a bit overthunk.

Any one happen to know what the thickness of the whole assembly is? And how far apart the bolt holes are at the timing cover?

I’m wondering if two of the “biscuit” style universal mounts would fit under there? I suspect they would fit side to side. Might interfere to the rear where the timing cover sticks out from the block.

That funky mount design was apparently a band-aid to keep a leaking front seal from deteriorating the rubber. If you went to "biscuit" style mounts you'd have the same issue. I think they'd work for a while, but may suffer the same fate as the originals as far as oil leakage. My front mount was just a mass of goo, because the front crank seal was leaking like the Exxon Valdez for years. The metal shield over the top is supposed to keep the oil off the rubber, but doesn't do a very good job. But I think with a speedy sleeve on the damper and a new seal, I should be OK till I croak with the original style. Then it'll be somebody else's problem.

Yeah. I think I could engineer a “biscuit cover”that works as well as the original oil shield.

Fixing one’s oil leak is probably the best way to go. Mine front seal definitely seeps. Not a big leak.