Pro's con's? I ran my '39 with a solid mounted 348 and never had a problem. Just wondering what other people have done.
I prefer to rubber mount an engine myself unless its a dedicated race car. A pro is that you can make the engine an integral part of the frame, like a big heavy cast iron cross member that way. You have to build your mounts pretty heavy for it to work that way. One thing to think about is that the rubber mounts were put there in OEM setups as a vibration isolater. So if your engine is a shaker you are going to feel it more through the chassis. If that doesn't matter to you then it isn't a problem. Think motor cycle. Most older bikes have solid mount motors. Many got a bad wrap because your hands would get numb on a long ride because if vibration in the handle bars. Just food for thought.
As with many things hot rod, what is right and what you can get away with often aren't the same. "Regular" cars have a lot of chassis flex. Although engines are sometimes used as a structural chassis part, there is no guarentee your installation won't excessively twist / flex the block. Even if the block is up to the task, somethingh has to accommodate the considerable amount of chassis flexing that's a normal part of driving down the road. Lacking that it's a matter of time before something fatigues and fails. A solid mounted engine would not make it through a manufacturer's durability testing. Whether you can do it without problems depends on your particular hardware, how it is used, and how much it is used. Noise and vibration aside, for a street car, even if it has a motor plate, it's best to attach it to the car with a mount or bushing that provides at least a little compliance.
I have been running my straight 6 for over 3 years solid mounted with no problems. But yes it would be smoother and quieter with it rubber mounted.
I usually run solid motor and a rubber trans because i have ripped alot more belhousings than blocks in half. my 55 has the polyurethane motor mounts and trans mount because of like someone stated above the vibration in my hands after two or three hour rides. but my around town or track vehicles are solid.
You know I have run a couple 1000 mile weekends in my truck with no noticable vibrations. Even ran back from Symco, WI over 7 1/2 hours only stopping for gas with no vibration problems that I can remember. But I guess it all depends on the vehicle of course.
The main purpose behind an isolated mount is to keep the mount itself from breaking do to fatigue. They do help with vibration and all that but that is not the main purpose. If you are having trouble finding mounts for your application or worried about expense try these guys. http://www.vibrationmounts.com/NewProducts/ I was able to find something that worked for my 38 Pontiac flathead, cost was around $30 all in.
I use the Old Ford biscuits on every thing,best of both worlds rubber that is solid and no worries of engine coming up with a broken motor mount such as stock Chevy front mounts did in the 60s.
If it's just a cruiser, use the rubber mounts. If it's a car you care about flexing (IE, a race car of some sort), use two motor plates and make it a stressed part of the chassis. I have hit concrete very hard in a car with a solid mounted engine, and run full seasons (20 some odd races) with the rev chip at 7800 RPM, and my blocks lived through all that just fine. The only time I ever broke a block was from rotating assemblies kinetically disassembling themselves (usually taking a pan rail or two with them). Done properly, you will tear the mounts off the chassis before you break the block anyway. If you solid mount the block, let the trans float or mount it in rubber.
Just as a side note, I believe different engine types will vibrate more or less. for example inline engines tend to run smoother (less vibration) where as v configured engines tend to vibrate a bit more. Generally speaking.
So..... Do you always run poly mounts in all positions? would you ever run rubber motor mounts with a poly tranny mount? or vice versa??
This old posting 2011,but some still look. If your not planning on lots of miles,hard mounts I think are kind of OK, if your too lazy to make rubber. Race only is another ball game. Vibs on long miles ,don't just bug those riding,also add to sound an work stuff apart,often add too or even start cracks. It's not rocket tech,we can get away with being lazy about some stuff,more so if you feel lucky.
Timely thread resurrection! I've recently raised the 350/350 combo in my '41 Chevy coupe as it was set way too low - new engine mounts on frame, gearbox crossmember modifications. When doing that I found one of the rubber engine mounts was knackered. No bother, I had a full set of poly Energy Suspension engine and trans mounts on the shelf so put them in. Test driven only last night for no more than 3 miles. They'll be replaced as soon as I can get rubber replacements! It's a mild street car. I've removed those urethene things pictured above on a previous car too. Don't like vibrations! Chris
I'm putting urethane mounts (engine and tailshaft) on my '32 racecar as I'm pretty sure I won't be able to tell what's vibration or lope.......
One thing I have heard of happening is the oil pump pickup cracking or becoming separated if it's a push in style with solid mounts. Particularly if you use a long, unsupported pick up tube. Iv'e been running solid mounts for 7-8 years with a rubber trans mount and haven't had any problems. It's and old car, it's going to vibrate a little anyways.
I have a matched ES set of motor mounts & trans mount in my car, quality pieces. I did use solid mounts in my stock cars, but not for long. Another racer crashed his car in practice so hard, with the solid mounts he tore the side of the block out where the mount attached.
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