Gonna be putting in a new 355 short block in the next week or two. Would it be wise to get new mounts? Would I need new mounts AND new inserts? Never done these before, someone point me in the right direction.

 

It'd be easiest to do it now.
Inserts should be all you need. Poly is the way I always go.

 

I would go and get some moroso solid mounts. I know you all are gonna have a stroke, but i run solid mounts and THE CAR WONT SHAKE ALL OVER like everybody is gonna tell ya. why waste HP and TQ letting that new motor twist in the bay???? PUT IT TO THE GROUND!!!!! Not to mention you'll never have to buy another motor mount again!!!!
I run a .284/.305 dur. .507/.525 lift shaft in an 11:1 383......mine dont "shake yer eyes out".....

 

Poly inserts is the way to go. Using all metal motor mounts is good for performance, but does put more stress vibrations in the drive train, in particular to the transmisson. The poly is a trade off between metal and rubber mounts. I had this discussion with 2 different transmisson builders(automatic) and they both told me the same thing. It can put strain on the trans housing and tailshaft. They also recommend a poly mount versus a solid mount on the transmisson for the same reason. Badman

 

Thanks guys, poly inserts it is.

 

Go that way if ya want. After the third (thats 3) $60 poly drivers side i cut my losses and solved my issues for good. Your choice. Just telling you my experience.

 

wow, someone is getting rich off you. where in the world are you buying parts?

 

Yes, now is the time to replace your motor mounts with poly mounts. New motor mounts will outlast you so I would not even think about solid, save that for the track if needed. When you use solid, the trans mount must also be solid or you will break your trans case, happened to me years ago.

 

I run solid motor mounts and a poly trans mount, no broken trans cases, the only time in these cars you'd snap a bellhousing is if you're using a solid trans mount as well since these aren't tube chassis cars with no flex.

 

I used rubber mounts. So the shell comes with the insert, for $12 a side.
I also used a rubber tranny mount. I'd recommend the poly though, I think mine is a bit loose for my tastes. It's LOADS easier with the engine out

 

all the solid motor mounts ive seen require a poly trans mount. unless its a tube chassis car.