Driver mount looks like a correct '66 Mustang mount, but the passenger looks like a 65 HiPo mount? What's the casting number on the pass mount?

In '65 Mustangs w/ V8s they had two engine mounts, one for the standard performance engines, and one specifically for the High Performance engines (which is what you have on your pass side); in '66 they simplified V8 engine mounts with just that single version you have on your driver's side.

I'd try jacking up both sides of the engine to see if either mount separates and then replace whichever side is bad with a matching mount.

 

Looking at this listing (link) you are correct on the passenger mount being a hipo mount. But I think the appearance of the driver side is deceiving. It's a solid block of steel welded in place of the rubber bushing. The block could be the same dimensions as the original, but that seems unlikely. As mentioned above, some of this rigging may have been done in a lame attempt to create clearance for the headers and clutch linkage. My concerns are more around the potential of having to redo all of my exhaust and clutch linkage to accommodate the correct mounts.

 

Driver's side looks correct to me. There is rubber on the engine side that's hard to see due to age/grime. When I replaced my engine mounts, I actually gained header clearance due to the increased thickness of the new rubber. No other issues encountered.

https://mustangbarn.com/wp-content/uploads/2023/03/1964-66-Smallblock-V8-Motor-Mounts.pdf

 

Driver's side looks correct to me. There is rubber on the engine side that's hard to see due to age/grime. When I replaced my engine mounts, I actually gained header clearance due to the increased thickness of the new rubber. No other issues encountered.

https://mustangbarn.com/wp-content/uploads/2023/03/1964-66-Smallblock-V8-Motor-Mounts.pdf

Not to sound contentious, but the block between the upper and lower mount on the driver's side is solid steel, and there are weld boogers all the way around it. He might have started with the original mount, but this block definitely appears different from what I see in that link you provided (pn 6038: insulator assembly).

 

This is the part that's rubber:

 

ok I see that now. I'd try sticking a magnet to that area and see if it sticks. if so, then I'd definitely replace that mount since you're going to cause vibrations to radiate through the unibody that might cause other issues. I've heard good things about the Ron Morris adjustable motor mounts if you're worried about keeping all components in alignment, however, a new motor mount is $20 so it might be worth it to try replacing both mounts with stock '66 styles first.

 

Magnetic:

 

yea the PO probably broke the driver's mount, since the torque of V8 engines pulls on this mount, and just welded it up to "fix" the issue. I've seen people add chains and do other similar things for race applications, but for the street, I'd install new insulated mounts. The Ron Morris mounts have a urethan insulator I believe.

 

So no concerns about the exhaust needing to be rehung or anything? It doesn't seem to have much give when it's unbolted from the headers.

 

Exhaust should all be hung with rubber mounts that provide some give, z-bar has adjustability if necessary, fan shroud may require adjustment, but otherwise I don't think you'll have issues. In my '66 with a 302, tri-y headers, and Toploader, I replaced only my broken/separated driver's mount, it raised that side of the engine about 1/4-inch, then I took the car the very next day on a 1000-mile roadtrip and had zero issues. Obviously only a single example, but I think if you replace both engine mounts with new '66 style mounts, such as the one's I used below, you'll be fine.

https://autosalesinc.pxf.io/c/40473...39/2996090/35994?subid=autolinker&u=https://www.summitracing.com/parts/ani-2257

 

Also, that passenger HiPo mount is worth some money so don't trash it. '65/early66 GT350's and HiPo (K-code) cars both used this unique mount and reproductions are pricey:

65-early 66 HiPo Mustang and GT350 Motor Mount Kit - Pair

www.virginiaclassicmustang.com

 

I think the pass mount is a standard 65 mount not a hipo mount.
If you want to replace with both with 66 style mounts you will nee a 66 style frame mount for the pass side as well as 2 new mounts.

 

The MustangBarn link I shared above shows the two '65 Mustang V8 engine mounts, and the OP's passenger mount seems to resemble the HiPo. The regular V8 mount has a curved metal section (6028/9) in the middle, whereas the HiPo has the large, tiered rubber piece (6038).

 

Actually, @kb65, I see what you're saying now. That curved metal piece(6028/9) might just be hidden due to the angle of the photo. Additionally, the OP's lower support bracket does seem to more closely resemble the curve of the standard '65 V8 piece. Think more photos are required to confirm, or that casting number is needed.

 

Either way, someone has been messing with the car. The "65" mounts were also used in 1966, up through 11/1/65. This car has one of each. Verify the build date of the car, and switch to the correct frame bracket and insulator.

 

Thinking ahead, should you decide to add headers, the Ron Morris mounts are the ticket to success. I have them an d the minion adjustments are greatly appreciated and they are quality too. If you are going to replace those mistakes anyway dd a little more for ease of fitment. Just my 4 cents.

 

I think this is
Non HIPO ‘65 mount?

 

I think this is
Non HIPO ‘65 mount? View attachment 921510

That is a a correct, non-HP standard 65-early 66 mount, for engine codes F, D, C, and A.

 

How easy is it to replace standard 65 V8 (289) mounts?
Can you just secure the engine (jack) and remove the mounts?

 

Thanks for the feed back, all. The casting number appears to match the HiPo pieces I've found, but it's moot since I've decided to go the route of adjustable RMPs (I got both standard and lower on the way so I have options). Will keep y'all updated if I run into any issues replacing them.