I'm going to be putting headers on my car, and may consider changing the motor mounts at the same time. How can you tell if your car needs new mounts. I'm the original owner and I'm sure they've never been changed. The car has about 100K miles on it.

Is there any reason I shouldn't just go with OEM mounts? What are the advantages of the poly mounts? If they increase vibration, I probably wouldn't be interested. I'm not really planning to do very much to the car. Initially, I'm just going to do a full exhaust and intake.

 

go stock then. Some can handle the vibration of a poly some cant. If you worried about it, then just go stock.

 

If you've ever felt the difference between rubber and poly on the trans -- changing the engine mounts over to poly does the same thing.

 

agreed

 

I've never felt the difference.

What would you say are the pros & cons of poly vs. the stock rubber mounts?

 

I did not like the poly mounts, the vibes were annoying, pulled them right out and put new rubber ones in which were vibe free.

 

This may be a stupid question, but does any other hardware, aside from the rubber inserts themselves, need to be replaced when changing the mounts? The OEM mounts are quite pricey, but I've confirmed that they're nothing but the inserts. Given the price, I thought you might get new bolts, etc., but that's not the case.

 

As long as the bolts aren't too rusty or cross threaded there shouldn't be anything else you would need to replace. Just for another point of reference, I put in poly motor and transmission mounts on my rebuild last winter... No complaints

 

I really didnt notice any extra vibration.

 

Me either, no extra vibrations with my poly motor mounts. I did notice how hte headers weren't banging off the k-member anymore.

 

I have prothane mounts for both the engine and tranny. Prothane is known for being a bit harder than energy suspension. I honestly have a lil bit of vibes but it's really minimal. On a cruise you'll likely never notice it and you have a much better mount. Before I put in the prothanes my headers would smack the floorboard taking off from a stop. I don't have that nonsense anymore.

 

So, your Kooks headers were hitting the floor board? I bought Kooks and their Y-Pipe. I was hoping that might only be an issue with cheaper headers. So, one reason to get poly mounts is improved engine stability?

How big of a pain is it to change motor mounts? It doesn't sound like fun.

 

It's really not as bad as you think. I looked at it and thought to my self "Self, this is gonna suck", but honestly I had it all done in a couple of hours.

My Kooks headers were hitting the floor b/c my mounts were junk, it was no issue with the header fitment.

 

that part of it is very nice

 

Changing the motor mounts while installing headers is a piece of cake because you'll have to have the motor mounts bolts removed anyway and the motor jacked up some to get them in.

If using a stock idle quality cam, you'll notice no vibration with poly unless the motor is idling rough for some other reason and then that needs to be fixed.

An alternative would be to only install a poly mount on the driver side and put a new OEM one on the pass side. That will give you all the motor stability you need to keep it from torquing over on hard accellerations and give you minimal change in vibration difference if there is any at all.

Now the tranny poly mount I did notice a difference, but I have no choice as it will break the LS1 mounts in less than 2 days driving usually because of the firm shifts.