There is a lot of confusion about engine mounts, especially when it pertains to swapping a big block engine into a Camaro. This page is designed to eliminate that confusion.
General V8 Information
From 1970 to 1971 - all Camaros used a "tower" style engine mount, where the BRACKET was on the frame and an insulating mount was bolted to the engine. It is possible for the mount to fail - the rubber separates from the mount, allowing 1 half to stay bolted to the engine and the other half to stay bolted to the tower. Most mounts, especially newer or replacement mounts are designed to eliminate this problem. Replacement mounts have a safety interlock, so if the mount breaks, the 2 sections can't "come apart" even though they're broken. Aftermarket mounts are designed to stay bolted together even if the insulating section separates from the steel plate its bonded onto.
View PRE-72 style:
Stock mount |
Stock side profile |
Aftermarket mount |
aftermarket side profile
Note: there's an additional steel plate that goes behind the above aftermarket mount. It's not depicted in the above photos.
There are TWO CONFIGURATIONS of mounts you'll see. The low powered V8, and the high performance 350 (i.e. Z28) and the "big block". You can easily screw this up since the mounts/brackets must be coordinated. So I'll step through it.
As mentioned above, there are 2 styles of mounts. "short & wide" and "tall and narrow".
Short & Wide measures 2 5/8 wide, by 1.75" high. This was used on low powered V8's - the 307 & 350 2-barrel.
Tall & narrow measures 2 3/8 wide, by 2 3/16" high. This was used on the Z28 and the Big Block equipped Camaros.
The "short and wide" can accidentally fit the narrow tower. Your question will be "why is there space between the bracket and the mount?".... cause you're using the wrong mount. The narrow mount won't fit over the wider tower. Then your question will be "WTF?". The problem is because you have a bad-ass engine, you bought the "350 high performance" mounts - but your car originally had a regular 350 in it. So you got the 2 5/8" wide tower on your subframe. So buy the short & wide mount and be done with it. The Z28 uses the same bracket as the big block. So here's some more confusion... is that the "big block" mount... or the "small block" mount? it's the tall & narrow - so match the mount and you're done.
The reproduction BRACKETS (or towers) on the market are the Big Block brackets. So these are looking for the NARROW mount. I guess the theory here is - the other bracket doesn't go "bad"... and you probably already have it. and if you want to swap to a big block - you need the different towers so you can fit the engine into the car properly.
Part # on the wide bracket is: 3980930 & 3984890 = 70-71 307 & 350 excluding Z/28
Part # on BBC tower: 3984886 & 3982307 = 70-71 350 Z/28, 396, 400 & 454
Part # on appropriate Clam-shell: 332648
Alternate clam-shell part #.
1972 & Beyond:
Beginning in 1972 engine mounting was simplified in addition to strengthened. The mount design changed to the "clam shell" style of mount, where a steel bracket was bolted to the engine and the insulating mount was contained within a steel cage bolted to the frame of the car. The "mount" on the engine is gone - it's now a BRACKET. The "mount" portion is a rubber block captured within a steel cage. This is replaceable, but even if this mount fails, you probably won't notice.
To make things even more simple, and economical for Chevy - the 396 and the small block V8 now share the mounting brackets. So, swapping a big block into a 1972+ Camaro is simple. If the car was a V8 to begin with - you already have the "big block" brackets.
The clamshell steel bracket that's been used throughout the years changes part #'s and THERE ARE DIFFERENT HEIGHTS available, depending on the original source of the bracket. The height of the clamshell from block mounting surface to the bolt hole center line needs to be 2 5/8". See this picture to see what I'm talking about.
If the bracket has come from a truck or something else - it's possible to be 3" high, which'll cause hood clearance issues, valve covers banging into a/c boxes, brake boosters, etc...
A word about headers:
When you want to swap a big block engine into your car - most places will say you need the "Big block" motor mounts. Remember, if you have a 1972 or later car - you already have the big block mounts. If you have a pre-72 car - or are using headers that are super large (i.e. 2"+ primary pipes) - then you MAY NEED TO OBTAIN & USE the official 1970/71 Big Block tower mount for the headers to fit. These may be bent to just clear the smaller profile of the tower mount. Typical, average street headers for a big block will fit using the regular clam-shell mount.
Subframes are drilled for every available mount combination for the year in question. Just that. So if you want to try and add the clamshell mounts to a pre-72 car, or vice versa (put the official big block towers into a 1972 or newer) - the holes will not be present on the frame. You'll have to locate & drill them. I don't have a template to locate the holes. Some subframes, especially in the mid 70's are drilled to accomodate the firebird equipment as well. Later subframes are easier to identify because they have 3 sets of holes for the different engine combinations available (i.e. 1980: chevy V6, buick V6, V8 chevy...)
Replacing mount on the frame:
If by chance you need to remove your mount/bracket from the subframe and the lower control arm is still in place - use a distributor wrench to sneak into the hole to catch the nut. There are 1 or 2 nuts that are difficult to get to when removing the bolt that secures the mount from the top side.
The drivetrain, by design on the Camaro is shifted to the right ever so slightly... 3/8 to 1/2" is typical. If you're swapping engine brackets and positioning the engine into place - keep this in mind.
6 Cylinder swaps. I'm unfamiliar with the 6-cylinder mounts, especially the later V6's. The only thing I can say here is to use the commonly available, year appropriate V8 mounts on your subframe and you won't have any problems. As mentioned above, the holes are already in your subframe for the V8 mount.
LS swaps. This is getting more & more common. This information is specifically covered in the "High tech retrofit" section of our discussion forum.
Author: MadMike Maciolek
North Georgia Classic Camaro
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