I have poly motor and tranny mounts I want to know how much movement there is going to be, I'm going to be fabricating a y-pipe and i plan on tucking it up as close as possible to the frame rails. How much clearance do I need to leave between the tubes and frame rails? For engine flex.

 

Since I've officially joined the DDA club today, you better wait for a verification, but ...

I believe the poly mounts "move" less than stock rubber - that's why some folks notice a slight rise when swapping to poly motor mounts (stock rubber compresses more under the weight), and why folks say the poly tranny mount gives more vibration (stiffer than rubber).

 

I was thinking 1/4 for clearance??

 

I hate to guess - I'd inevitably be wrong. These are the types of things in my life where, Murphy always steps in and reminds me about laws that shouldn't exist.

Maybe someone else will chime in.