I recently purchased some NOS Chevrolet upper rear subframe mounts and also purchased a supposedly NOS Firebird upper rear subframe mounts but the holes where the bolts go through from the inside of the car look different size than each other but the width and heights and structures are the same can anybody tell me if they are supposed to be alike seeings how subframes are compatible with the different makes of models, or give mr the correct factory number for the upper rear subfame mount? Thanks Dan [email protected]

upper and rear would be 2 different things. you have front middle and rear rubbers. the middle and rear are the same size in diameter but different in size somehow. they have a diagram for it when you buy the kit. i can look tomorrow for the instructions. i bought the camaro/firebird mounts with hardware for 65$ came with different bolts and size specific rubber in specific locations. mounting hole is 1 1/2" in diameter. the rears are higher if i remember right. middles slightly thinner than rear and the fronts are essentially a cushion style.

hope this isnt too much rambling for you or confuses you more than you are already! if you need dimensions ill get those for you as well for the height!

Here's a good description of the subframe bushings from the Camaro Resoration Handbook:

The rear cushion set is the smallest; the outside diameter of both cushions measures about 2-1/8 inch. The center cushion set is a little different. The upper cushion (with the washer and the bushing) has an outside diameter of 2-1/2 inches. And the outside portion of this cushion can be identified by its height of 7/8 inch. This height is measured without the washer. For all practical purposes the cushions that don't have a washer for the rear and center cushion sets are interchangable. The cushion set that's used for the radiator core support also has an outside diameter of 2-1/2 inches just like the center cushion. However, it can be differentiated from the center cushion by its height; it's only 9/16 inches tall excluding the washer. And because of its unique (smaller) bushing diameter, only one of the washerless cushions will fit it.

When they talk about washer-less cushions - they means the halves without the metal inserts/sleaves. Hope this helps.

Well not really but Thanks I will try and explain again the two most rear subframe mounts one Firebird and one Camaro have different size bolt inserts the one mount for the Firebird which is blue rubber in color I believe has a smaller bolt hole than the Camaro. Now they are both the same height width and length but you would think the bolt holes would be the same? Guess I will have to wait and tear them off to find out???

Maybe that is what the washers are for?

I also have some NOS mounts for sale on Ebay right now but don't know if the rear ones fit Firebird's.

I had a 4 piece NOS set i bought for my 68' but did not end up using them.They where all marked Chevrolet. If yours are, you should fetch a good buck for them.Could not sell them here for $20 shipped and some Camaro guy jacked them up to almost $500 U.S. However i'll take them off your hands for $30
Here is a picture of the set i had.Read Salmon's previous post about sizing.


David

the hole size shouldnt make much of a difference. that is exactly why the washers are there. the larger hole size means more adjustment available in the frame.

Thanks for the insight on this matter I appreciate it Drew.

i repaired my mounts and used a kit for it. i have around 1" of total adjustment in the frame so i can true up the car. you'll just have less!

Why is this topic still at the top of the list?

dunno! has been here for 2 weeks!

I guess I made a error on the mount location, the mounts I was talking about are for the center of the subframe that have the different bolt sleeve diameters. Hope this gets this topic off the top of the tech list.

I asked that this be made a sticky because we see somebody asking about what mount goes where every couple of weeks or so. It appears that nobody sends instructions with the subframe mounts.

Not to get off the subject, but what mounts are prefferred and why?

Meaning, rubber, poly, ect. For a non "correct" car, is one better than the other?

Dave

depends on a variety of factors. subframe connectors or not. racing or street driven. list goes on and on!

Heck, why throw solid (aluminum) bushings into the mix, too.

You should see the raging debates on this question over at the Team Camaro (1st Gen Chevy) boards.

The autocrossers swear by solid bushings, especially if one is going with subframe connectors. Others claim it's like having your drivers seat bolted to the rear axle, others say go poly as it's a nice compromise, others say poly is also too harsh of a ride ...

Not just solid mounts in the mix, but you can also get 1/2" drop mounts.
I changed the 428 car to standard Poly, I'll change the track car to solid with subframe connectors, maybe even dropped, but the vert will stay stock rubber.

Nice to have options these days.

I use solids. Love them. People claiming a harsh ride must be running super-stiff springs (mine are 380lbs/in). Although most of the people that make that claim never have actually installed them. My other guess is they change them along with other stuff such as poly control arm bushings, bigger rollbars, stiffer springs, stiffer shocks etc. and then blame the subframe bushings. I only changed the bushings first when I test drove it.

Thanks for the feedback.

I am planning on 100% street car with subframe connectors. This is a vert with a mild 455.

Dave

Then keep the springs mild and make the chassis as stiff as possible.

Thats a BIG 10-4, Mike!!!