Mustang MonthlyHow To Engine
How To Identify And Choose Engine Mounts
Selection isn’t only about vibration isolation but also driveline angle,function, and clearance
Engine mounts exist to provide support and isolate vibration. As the Mustang evolved over the past half century, engine and driveline mount technology has advanced to where high-tech vibration isolation makes the drive smoother and quieter. Fifty years ago, Ford used thick molded rubber stock, which continues to do its job quite well. These days, you have quite a choice of engine mounts for older Mustangs—original equipment rubber mounts, harder urethane mounts, and specially engineered aftermarket mounts designed not only for quiet but also strength.
When the Mustang was introduced in 1964, it had engine and transmission mounts borrowed from the Falcon/Comet, which didn't offer sufficient vibration and sound absorption for a class act like Mustang. If you drive a '65 Mustang with a 289, then hop into a '66 with the redesigned "C6ZZ" engine mounts and you can feel the difference.
Vibration isolation and harmonics is a tricky science that requires an understanding of engine mounts and how they evolved during the Mustang's first 14 years of production. For this article, Garrett Marks of Mustangs Etc. hauled out a smorgasbord of '65-'78 Mustang mounts—new-old-stock, aftermarket replacement, used, and urethane—from his inventory and came up with part numbers, applications, and change dates. We learned there were engineering changes along the way intended to improve vibration isolation, safety, cost, and fit. The trick is choosing the correct mounts for your application.
According to Garrett, six-cylinder Mustang engine mounts and body brackets were cast-iron from '64½ through '70. There were three basic types—'65-'66, '67-'69, and mid-year '69-'70 designed for both the 200 and 250 sixes. Body brackets were stamped steel for '71-'73.
From '64½-'70, there were also two types of six-cylinder engine mounts—one for hardtop or fastback and another for convertibles to lower the installed engine height by ½-inch. It appears the reason for that ½-inch height difference was exhaust pipe and driveline clearances with the convertible body structure.
When the Mustang entered production in early 1964, it was fitted with off-the-shelf parts from Falcon/Comet, including engine mounts and brackets. Owners of '65 Mustangs can use the original Falcon mounts and brackets or switch to the improved C6ZZ versions that were implemented on November 1, 1965. The C6ZZ mount and bracket were a totally new assembly designed to reduce noise, vibration, and harshness along with reduced manufacturing cost. Prior to November 1, 1965, the Falcon-based engine mount was a three-piece affair with a body bracket, mount, and "L" bracket, which didn't do its job as well and was more costly to manufacture. A great advantage with the C6ZZ mount is clearance; it takes up less space, making it ideal for aftermarket headers and 289 High Performance exhaust manifolds.
Where the improved C6ZZ mount gets confusing is its dimensions because there were two types. If you've ever tried to replace small-block V-8 engine mounts in a '67 Mustang or a '68-'70 convertible with off-the-shelf replacements from an auto parts store, you may have discovered this difference the hard way. Although V-8 body brackets look the same at first glance, they're different dimensionally for a reason—installed engine and driveline height, which is a ½-inch difference. Because convertibles have more body structure underneath, it became necessary to develop a body bracket and engine mount combination that would lower the engine's installed height by ½-inch.
Not only do convertibles call for this bracket and mount combination, so do '67-'70 390/428ci big-blocks according to Garrett's extensive research in the Ford Master Parts Catalog. Small-blocks call for this mount for driveline and exhaust system clearance with a convertible's complex underbody structure. With a big-block 390/428 ('67-up), it's the same reason coupled with air cleaner to hood clearance issues.
Because the '71-'73 Mustang is more like the Fairlane/Torino, there's a vastly different engine support system. For '71-'72, engine mounts are the same with stamped steel body brackets and traditional rubber mounts. For '73, federal safety mandates called for sandwich-style mounts, which called for redesigned brackets.
Better Aftermarket Mounts
With better technology has come a crop of aftermarket engine mounts for classic Mustangs. The most obvious types are urethane mounts from Summit Racing, Mustangs Etc., and Mustangs Plus. Summit offers a huge variety of high-quality cadmium-plated urethane mounts from Prothane, which fit the '66 and '68-'70 non-big-block/convertible body brackets. If you have a '67 or '68-'70 with big-block, convertible, or Boss mount brackets, you will have to change the body brackets to achieve a proper fit because the aftermarket generally does not recognize this dimensional difference. Mustangs Etc. carries the Mity Mount from Dyna-Tech Engineering, which is an enclosed safety link mount for '65-'72 Mustangs.
Another option for owners of '73 Mustangs (and '83-up Mustangs with the 3.8L V-6) is remanufactured engine mounts available on an exchange basis from Mustangs Etc. You provide them with your old mounts and they provide you with a remanufactured piece ready for installation.
Which type of engine mount and bracket combination you choose for your classic Mustang depends largely on how you intend to use the car. A concours restoration calls for factory-style rubber mounts whether they're aftermarket replacements or new-old-stock originals. Your search begins with knowing how your Mustang was equipped in the first place, what will fit, and what will work best for your project.