351c motor frame mounts

[ScottM]

So I guess I ended up with 73 vert mounts for my 351c swap. they don’t line up. I believe I have 72 motor mounts on engine. Anybody have 71-72 vert mounts? Or is it possible to just drill out the 73 vert mounts? Or go with prothane after market?

Frustrating as heck on all the different ford mounts…arggggh

 

[Robsweden]

I used the energy suspension for my 351c and 73. I just relocated the frame mounts with some steel plate and it works perfect.

 

[ScottM]

I'd like to know exactly what the difference is between the 71-72 and the 73 vert pedestal beside the hole alignment. I just wonder if the angle and height is the same. Would love for some experts to advise on this.

 

[Hemikiller]

View attachment 71-73-Motor-Mounts.jpg

 

[ScottM]

@Hemikiller well from that diagram it seems that I have the correct pair of 73 motor and frame mounts. Question then is why is the center not lining up? It fits over the frame pedestal just fine but is off by about 1" on the bolt hole.

It is a 71 vert that I have swapped a 351c into from a 73 cougar.

I believe I have a 73 convertible frame mount for the 351c...are there two different engine mounts for a 73 hardtop and convertible?

 

[ib4stangs]

Actually, according to this article, yes...(photo# 18)

secluff would be your part ID source.

https://www.motortrend.com/how-to/mump-1302-how-to-identify-and-choose-engine-mounts/

 

[Hemikiller]

@Hemikiller well from that diagram it seems that I have the correct pair of 73 motor and frame mounts. Question then is why is the center not lining up? It fits over the frame pedestal just fine but is off by about 1" on the bolt hole.

It is a 71 vert that I have swapped a 351c into from a 73 cougar.

I believe I have a 73 convertible frame mount for the 351c...are there two different engine mounts for a 73 hardtop and convertible?

Yes, the convertible and fixed roof cars used different frame stands and insulators. The angle of the mount was different on the convertible to combat a vibration unique to the chassis.

The compatible families are:

71-72 Hardtop/sportsroof - uses Anchor 2257 insulator

71-72 convertible - no aftermarket insulator available regardless of what the parts catalogs say.

73 Hardtop/sportsroof - no aftermarket insulator available - OE mounts are rebuildable by Mustangs Etc

https://www.mustangsetc.com/73-mustang-302-351-motor-mount-rebuilt-fits-coupe-fastback/
73 convertible - no aftermarket insulator available - OE mounts are not yet rebuildable, the insulator blocks are unique.

 

[ScottM]

Looks like if you own a convertible of any kind you are just on your own

 

[Hemikiller]

Looks like if you own a convertible of any kind you are just on your own

The only solution at this point is to swap for the 71-72 fixed roof parts. I have heard that Mustang Barn in PA can modify the 2257 mount to work for the 71-72 droptop stands.

 

[rackerm]

Looks like if you own a convertible of any kind you are just on your own

Unfortunately, Hemikiller is correct as always. When I spoke a few months ago with "thee" guy at Mustang etc. He said they were working on getting the rubber insulator for the 73 verts. He seem hopeful that it would happen but he offered no timetable as to when. If you can use a pair of 71-72 or 73 vert or hardtop frame mounts, I have a collection of them. I would be interested in your 73 Vert mounts.

 

[351c1971]

The 71-72 frame mounts will work, however Prothane motor mounts will only work with 351C 2v exhaust manifolds due to clearance issues. If you use the Prothane mounts, you will also have to cut the tab off on the frame brackets.

 

[ScottM]

Unfortunately, Hemikiller is correct as always. When I spoke a few months ago with "thee" guy at Mustang etc. He said they were working on getting the rubber insulator for the 73 verts. He seem hopeful that it would happen but he offered no timetable as to when. If you can use a pair of 71-72 or 73 vert or hardtop frame mounts, I have a collection of them. I would be interested in your 73 Vert mounts.

The mount situation on these cars are the only real nightmare that I have come across in this rebuild. Couple more questions for whoever...

1. Will a set of hardtop mounts (frame/insulators) work on my vert?
2. Am I correct in understanding that this will raise the engine 1/2"?
3. Will that change my driveline angle?

I'd be willing to do some trading of what I have for a matched pair...

 

[rackerm]

The mount situation on these cars are the only real nightmare that I have come across in this rebuild. Couple more questions for whoever...

1. Will a set of hardtop mounts (frame/insulators) work on my vert?
2. Am I correct in understanding that this will raise the engine 1/2"?
3. Will that change my driveline angle?

I'd be willing to do some trading of what I have for a matched pair...

It sure is a mess and difficult to sort out what's what! I can't imagine all the variations in driveshafts Between Engin/Trans and rear axels 8" 9", Gear ratio, and 28 & 31 Spline. No wonder Ford build Sheets needed 4 color code bands to get 24 combinations to cover all the drivetrain combinations available on a Mustang/Cougar. That's why Ford used color codes when picking some parts on the assembly line, it was less error-prone than reading part numbers. Anyway, I probably read it in your posts, but please confirm your car is a....

Year: 1971 Mustang
Model: Convertible
Engine: 351C
Trans: factory C4, C6 or FMX, or a manual 3 or 4-speed Toploader: Yes
Factory ride height: Yes
and you are looking to maintain factory engine height and driveline angle and ...Correct?

71-72 Convetible/429ci Frame mounts paired with 71-72 Motor Mounts. I have the frame mounts and the motor mounts, but you can easily get the motor mounts from your local parts store or online. It's your call on those. Message me if you are interested in them.

The total height from where the frame mount (perch) bolts to the cross-member and to the very top of the complete assembly should be 6 1/8". If it comes up short, it will not meet your block's mount holes correctly and the engine will not be at the right height.

 

[ScottM]

It sure is a mess and difficult to sort out what's what! I can't imagine all the variations in driveshafts Between Engin/Trans and rear axels 8" 9", Gear ratio, and 28 & 31 Spline. No wonder Ford build Sheets needed 4 color code bands to get 24 combinations to cover all the drivetrain combinations available on a Mustang/Cougar. That's why Ford used color codes when picking some parts on the assembly line, it was less error-prone than reading part numbers. Anyway, I probably read it in your posts, but please confirm your car is a....

Year: 1971 Mustang
Model: Convertible
Engine: 351C
Trans: factory C4, C6 or FMX, or a manual 3 or 4-speed Toploader: Yes
Factory ride height: Yes
and you are looking to maintain factory engine height and driveline angle and ...Correct?

71-72 Convetible/429ci Frame mounts paired with 71-72 Motor Mounts. I have the frame mounts and the motor mounts, but you can easily get the motor mounts from your local parts store or online. It's your call on those. Message me if you are interested in them.

The total height from where the frame mount (perch) bolts to the cross-member and to the very top of the complete assembly should be 6 1/8". If it comes up short, it will not meet your block's mount holes correctly and the engine will not be at the right height.

View attachment 74667

@rackerm

1971
convertible
351c
FMX

I have 1" lower springs on front.
I don't plan on using RAM air so I don't think it would matter if the engine is up 1" -- as long as the hood will close
I would like to keep the original driveline angle if possible...if not I can always shim the rear springs.

I currently have:
1973 convertible/429 frame mounts (I bought these thinking that the 73 insulators were the same)
1973 hardtop insulators

I just need the most cost effective way to make it work

 

[rackerm]

@rackerm

1971
convertible
351c
FMX

I have 1" lower springs on front.
I don't plan on using RAM air so I don't think it would matter if the engine is up 1" -- as long as the hood will close
I would like to keep the original driveline angle if possible...if not I can always shim the rear springs.

I currently have:
1973 convertible/429 frame mounts (I bought these thinking that the 73 insulators were the same)
1973 hardtop insulators

I just need the most cost effective way to make it work

No worries. See the message I sent you.

 

[ScottM]

So if the crossmember on these cars are the same…can I put 1973 hardtop sbf frame mounts and 1973 hardtop sbf motor mounts/insulators on a 1971 vert 351c and the holes will line up?

I’ve seen all the pics and I understand different mounts are not interchangeable but will they work on all 71-73 as long as they are same family be it vert or hardtop?

@rackerm has been really helpful but am I missing something

 

[351c1971]

I believe they will bolt up. The motor will be located 3/8" to 1/2" higher, which might create hood clearance and/or harmonics issues as noted earlier in this thread.

 

[rackerm]

So if the crossmember on these cars are the same…can I put 1973 hardtop sbf frame mounts and 1973 hardtop sbf motor mounts/insulators on a 1971 vert 351c and the holes will line up?

I’ve seen all the pics and I understand different mounts are not interchangeable but will they work on all 71-73 as long as they are same family be it vert or hardtop?

@rackerm has been really helpful but am I missing something

Scott,
I guess in theory what you say is correct, provided all other things are equal, but they are not equal or the same between the hardtop and vert. Your set might work fine on a 71,72,73 Hardtop because it was designed for a hardtop and assuming there were no engineering changes year to year to the cross-member affecting the mount location or angle..

The problem is ford may have made significant changes between body hardtops and verts and also between model years. We don't know what modifications Ford may have made to the chassis and cross-member. Especially in 1973, when the list of one year only parts is long. A personal experience I had once, I took radiator support from a 72 hardtop and installed it on my 73 vert. It installed no problem, but then I tried to install the one year only large 73 I-beem bumper support brackets to the frame rail and they hit the underside of the rad support. I then realized that the cutout in the radiator support was slightly larger on the old 73 support than it was on the 72 to accommodate these obnoxiously large 73 brackets.. Who knew?

My point is it the difference only between the vert and hardtop cross-member or the result of cross-member engineering changes between model years, or both? Who the hell knows? What I do know is the parts are different for a reason and for cost reasons Ford would on ly do it if they had to.

 

[351c1971]

This Motor Trend article might be of interest:
302 Engine Swap in a 1972 Mustang
https://www.motortrend.com/how-to/302-engine-1972-mustang-part-2/They shimmed the convertible mounts to hardtop specs.

 

[rackerm]

This Motor Trend article might be of interest:
302 Engine Swap in a 1972 Mustang
https://www.motortrend.com/how-to/302-engine-1972-mustang-part-2/They shimmed the convertible mounts to hardtop specs.

Sure give that a try. The angle at the top of the frame mount is different between the two mounts, but maybe it will work. The longer mounting bolts will be taking on more lateral stress, I would think about upping the diameter of the mounting bolts.