Why Flip Motor Mounts L-R and R-L?

1907 Views 18 Replies 8 Participants Last post by GasTungstenArc, Feb 1, 2022

GasTungstenArc

Discussion Starter · Jan 26, 2022

As I plan my V8 swap, I am a bit puzzled by one thing: why flip the engine mounts from left to right and right to left? As far as I have seen, the left and right mounts are the same.

This question refers to the swap route taken by some in which new engine mount holes are drilled/created in the subframe 3" forward of the old holes and the mounts are swapped side to side. Those who buy the swap brackets from JTR are in a different boat.

1 - 19 of 19 Posts

markmitch

· #2 · Jan 26, 2022

Actually there is an easier way, by the way I have no clue why some say to swap them, If you buy two sections of 1/4 inch steel plate I started with 6" X 6" leave frame mounts where the are, using the steel pates you can bolt the steel to the engine block allowing you to bolt the stock block mounts forward of where they were originally. I will see if I can get at least one side picture taken to show you how I have done it but mine is an AWD now. I did the same on a rear drive van in the past.. Let me know if you want me to try to take a few pictures.

GasTungstenArc

Discussion Starter · #3 · Jan 26, 2022

markmitch said:
Actually there is an easier way, by the way I have no clue why some say to swap them, If you buy two sections of 1/4 inch steel plate I started with 6" X 6" leave frame mounts where the are, using the steel pates you can bolt the steel to the engine block allowing you to bolt the stock block mounts forward of where they were originally. I will see if I can get at least one side picture taken to show you how I have done it but mine is an AWD now. I did the same on a rear drive van in the past.. Let me know if you want me to try to take a few pictures.

You used the plate as an extension to move the mounts forward?

I don't mind doing the work to convert. I have all the welding and fabrication equipment I need to do most anything.

markmitch

· #4 · Jan 26, 2022

OK I will take a few pics tomorrow and post them

AstroWill

· #5 · Jan 28, 2022

Moving them forward FULL Length Headers V8 Astro?

Not sure which year/awd etc. Maybe post the link to the thread you are referring to.

markmitch said:
OK I will take a few pics tomorrow and post them

Here ya go: home made v8 motor mounts

GasTungstenArc

Discussion Starter · #6 · Jan 28, 2022

AstroWill said:
Moving them forward FULL Length Headers V8 Astro?

That might be the first time it was mentioned. I saved the images of the modified mount positions for future reference. The "flip side to side" part is echoed elsewhere. I'm sure of it, but I have not found where it was said elsewhere.

Anyway, the engine mounts sure look symmetrical to me. Maybe they have an offset too small for me to see in the pictures of them that I have seen. Maybe if you didn't flip them side to side, then 3" isn't enough offset to relocate the engine mounts. Sometimes I think that maybe people are saying to flip the mounts under the same logic as rotating tires, but the thread you linked says that it has to be done.

PrairieDog

· #7 · Jan 28, 2022

GasTungstenArc said:
The "flip side to side" part is echoed elsewhere. I'm sure of it, but I have not found where it was said elsewhere.

I had read the same thing multiple times before doing my AWD. I had my hands on the JTR book a decade or more ago and seem to recall it from there also but can't absolutely confirm that's where I initially read it.
Once I got my hands into it all, V6 & V8 mounts side by side, I personally chalked it up to so much folklore. Since I saw no benefit in swapping the rubber mounts side for side, I did at one point wonder if the people making the statement were referring to the metal bracket that bolts to the block instead of the actual rubber mount; but going my own route I tossed the idea aside as conjecture and wasted no further energy on it.

I will be watching though, to see what comes out of the question.

GasTungstenArc

Discussion Starter · #8 · Jan 28, 2022 (Edited)

PrairieDog said:
I did at one point wonder if the people making the statement were referring to the metal bracket that bolts to the block instead of the actual rubber mount; but going my own route I tossed the idea aside as conjecture and wasted no further energy on it.

OK, that's a possibility. I hadn't considered the bracket. Everything I see says that the engine mounts are the same PN left and right. So either it's all hooey or we are missing something.

I just went back and looked at the "Full Length Headers V8 Astro" thread and noticed that he said "To make this work you HAVE to take the engine mounts OFF the V6 and flip them side for side." He said "off the V6." The mount wouldn't be on the engine; the bracket would. The mount is installed on the subframe and the bracket is on the engine. You might be right about this.

AstroWill

· #9 · Jan 28, 2022

GasTungstenArc said:
To make this work you HAVE to take the engine mounts OFF the V6 and flip them side for side." He said "off the V6." The mount wouldn't be on the engine; the bracket would.

This is what I was thinking as well.

PrairieDog

· #10 · Jan 28, 2022

GasTungstenArc said:
To make this work you HAVE to take the engine mounts OFF the V6 [snip] The mount wouldn't be on the engine; the bracket would. The mount is installed on the subframe and the bracket is on the engine. You might be right about this.

I'm not so sure I was. Thinking through it, the V6 brackets are what create the offset to the passenger side. Swapping them left to right definitely would not work.

I'm more inclined to agree with your "hooey" assessment.

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AstroWill

· #11 · Jan 28, 2022

I also wonder if it's different year/awd related?

M_a_t_t

· #12 · Jan 29, 2022

I don't think the offset is from the brackets on the engine. They are very close to the same. Maybe it is more obvious on a 2wd frame?

I got a picture I think would help but it's on my PC at home. I will post it later

Rod's Trucks

· #13 · Jan 29, 2022

PrairieDog said:
I'm not so sure I was. Thinking through it, the V6 brackets are what create the offset to the passenger side. Swapping them left to right definitely would not work.

I'm more inclined to agree with your "hooey" assessment.

When I first saw that picture, I thought : He has a stick shift!
Rod J

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M_a_t_t

· #14 · Jan 30, 2022

The angle kind of messes it up, but that crossmember is centered left to right between the side members. By spacing the one motor mount up (at an angle) it shifts it over to be narrow enough to fit the v6. If you look at the motor side brackets next to each other they are almost the same.

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Bikley

· #15 · Jan 30, 2022

Rod's Trucks said:
When I first saw that picture, I thought : He has a stick shift!
Rod J

That picture makes my JTR mounts look anemic.

Mmusicman

· #16 · Jan 30, 2022

This was a full-length headers "test fit" I did with my last 92 V8 installation.
It shows the interference with default engine motor-mount position on PS.
(it doesn't show if there is any further sub-frame interference)

Sidenote: These are Hooker SuperComps I intend to use next time engine is out, probably with my 400. (I will relocate the PS mount forward)

Motor vehicle Automotive exhaust Automotive design Automotive tire Automotive lighting

Motor vehicle Bumper Hood Automotive tire Automotive design

Driver side is tight (with these particular headers) but does not seem to be a big issue...

Automotive tire Motor vehicle Automotive design Bumper Automotive exhaust

With my 2000 AWD... I expect the resolve any sub-frame header interference issues by simply raising the engine (plenty of room for engine to go up with body lift) and if I go with full-length on my 2000, I'll likely be moving the PS mount as well.

Quite frankly, the Hedman 68600 block huggers are quite ideal for most performance applications... with the exception of the AWD PS interference. I just happen to have these Hookers sitting around, looking for a home in one of my engine bays.

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GasTungstenArc

Discussion Starter · #17 · Jan 31, 2022

I will understand more of this and will be able to distinguish truth from legend when I get mine apart. I wish I could confirm for certain that 3" is the number since the source for the 3" forward movement is also the one who say that the engine mounts have to be flipped. One claim casts doubt on the other, you know?

Whatever I do find, I will report on it when I do the swap. And maybe once that is done, we can pin the information for others who come after.

While we're at it, does anybody have a driver side engine mount tower from a 2WD van to sell me?

GasTungstenArc

Discussion Starter · #18 · Jan 31, 2022

Mmusicman said:
This was a full-length headers "test fit" I did with my last 92 V8 installation.
It shows the interference with default engine motor-mount position on PS.
(it doesn't show if there is any further sub-frame interference)

It would be nice to know if there were any other interference. Obviously, the subframe engine mount relocation would fix the engine mount clearance problems.

GasTungstenArc

Discussion Starter · #19 · Feb 1, 2022

AstroWill said:
Moving them forward FULL Length Headers V8 Astro?

Not sure which year/awd etc. Maybe post the link to the thread you are referring to.

Here ya go: home made v8 motor mounts

I knew I had seen it elsewhere:

www.astrosafari.com

V8-350 Swap 92 Astro

The old 4.3 in my 92 Astro made it to 282,000 original miles! A recent tick that developed into a knock turned out to be a broken piston skirt...not sure how it happened. Oil pressure still strong. I'm swapping with a 350. I have no intention of using the computer. The 350 engine is...

www.astrosafari.com

www.astrosafari.com

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