Just pulled the engine out to put a cam in car,but one of the motor mounts was melted,and I don’t think they were original mounts,but could be I guess,so my ? is what are the best mounts to put back,and to also give me the tightest fit,because I already know I will have hood clearance issues so don’t want anything that makes engine higher, thanks.

 

I guessing melted = poly type motor mounts, usually rubber mounts split / tear apart. All factory style mounts should put the engine in the same place.
Solid mounts are best to prevent the engine from moving while the engine tries to troque during accelleration / de- accelleration. Tighest fit / less movement period.
Poly is still stiff but melts to easily if exhaust is near by (header tubes)
Rubber is factory and allows the most engine movment. This is prefered to prevent / isolate engine vibration tranfering to the frame which at times can be felt in the driver seat. ???? not always.

I have drivers side as a solid mount & passenger side as rubber.

 

Solid on both sides is imop the best way to go

 

I melted my poyurethane ones on my big block and tore up the ones on my small block...solids have never failed, but do continue to use a rubber / poly one on the tranny

 

Sold in pairs for a reason, right?

 

Ok....for those that don't like a rubber on passenger with solid on driver......why? Can you explain?

 

whats the benefit? they usually break on the drivers side but I had cars with them broken on both,,,its not going to stop any vibrations because there isnt any that you would feel if you use a tranny soft mount

 

The point has been made before that if you use solid mounts on both sides.....the engine block is now a structural member. I honestly don't know if its an issue or not,....but I do know the frames flex alot. Is it possible that flexing would induce stresses into the engine block....hell, I don't know. Another forum dilemna to figure out, with multitudes of opinions.....and no engineering expertise. Drives me crazy. I get tired of the "over-thinking".....but I also don't want problems. I have had my share with this 406 engine build, and enough is enough.

 

The engine as a member would stiffen the frame. Using a full crossframe mount that is tied to the front of motors has been used in drag racing for years. Its like a giant gusset In old box frames.
Now all the racers have multipoint tube frames so there is no need.
If you have broken a mount or melted one. Why replace it with the same thing that will fail again?

 

I understand the engine stiffens the frame.......but what does that do to the engine? Is there potential for cracking a block?

 

One for each C3!

But seriously, why wouldn't you use both?

 

You apparently missed my responses......what does it do to the engine? Are there any qualified folks on this thread that can address the stresses that the twisting frame will put into the engine block,....and what potential issues that can cause?

 

If you are looking for a research paper on this, try the link below. Otherwise, there are lots of anecdotes on this Forum. I don't recall anyone saying their engine block had been ripped apart, but I might have missed it. If it has happened, perhaps they will respond to this thread.

If your engine builder says one solid, one rubber, and no vac advance, what expert will you find on this Forum to contradict that for free?

https://www.sae.org/publications/technical-papers

 

See if any of these sentences have a common denominator:

Only swapped out the rear U-Joint on the driveshaft and not the front.
GM 6 cyl, only changed out the front 3 sparkplugs.
Only changed the inboard brake pad, not both.
Only swapped out one old heater hose.
Only installed one Solid Motor Mount.

Half-assed job.

 

Ok, I can see the only responses come with attitude instead of a technical response. See ya.

 

The usage of solid mounts to limit engine movement, while gaining the added benefit of adding the engine itself as a structural modification to the frame is about as old as some of the guys here. Absolutely the only way to do that would be to use both steel mounts as a pair. The only time rubber mounts come back into play when trying to limit engine torque over would be to use two rubber/poly mounts and a torque strap. ( like a chain bolted to the frame, and the driver side of the block) Leaving just enough slack to allow the engine mounts to absorb/dampen engine vibrations, but stop the engine from trying to rip the driver side mount apart.
The only instance where related drivetrain breakage occurs when using solid mounts is when the transmission is also solid mounted, or limited through some semi-solid mount like a poly mount.
What happens is that now the engine twists with the frame, and the transmission has to take up some of that movement. A solid mounted trans breaks, not the engine itself ( usually at the bellhousing).
As long as a rubber tail shaft mount is used, then that usually suffices to absorb that twist, not just from engine torque, but as a result of daily driving.

There now,….No attitude, no overthinking, just another unsolicited opinion.
Happy?

 

There is nothing to worry about at all. Except internet chatter.

 

There is no way the frame would do any possible damage to the engine....you have too many parts down stream to absorb any amount of torque that would rip an engine block apart. I have seen engines and drivelines hook up and ripout the motor mounts and twist onto their sides, but the engine itself was still in one piece.

 

General Rules for Mounts:

Rubber front, rubber in back.
Steel in front, rubber in back.
Steel in front, steel in back.
But never-ever rubber in front, steel in back.

 

This is from "Chevy Performance" by John Mechelsen, page 17.

"Solid mounts have been popular in drag racing, but they create torque stress in the cylinder walls next to the motor mounts. A better plan is to use cushioned mounts and restrict engine movement with a torque strap at the front of the motor."