I'm in the process of making motor mounts myself. My original ones are pretty toast, the aluminium one is in two pieces already.

When I meassured the height of the original mounts there was a difference of 6mm, the steel one was 48mm and the aluminium one 54mm.

Is that normal or is that due to the fact that the aluminium mount was ripped apart? I reassambled it in the same position where it was ripped and pressed it down when meassuring. Maybe not enough?

The second question: I use polyurethan with a shore index of 70 A, which has to be considerably harder than the original rubber. Wouldn't it be necessary to make the new mounts less in height? I would assume that the original mounts are compressed much more by the weight of the engine than the poly ones.

Other than that, I wondered if it would be possible to lower the engine even more (compared to the original height) for an optimized center of gravity. Could this cause problem with the propshaft or the differential? I was thinking in the 10-20mm region.

 

Did nobody ran into this problem when making DIY motor mounts?

 

Probably because it's easier to just buy them.

The AL mount is different than the steel mount. My experience....

https://www.rx7club.com/3rd-generati...nment-1085345/

 

Thanks a bunch, that answers my question.

Where does which mount (Al/ steel) belong? Its a RHD car..

I havent memorized that unfortunately ..

 

The cast iron mount goes on the turbo side of the engine, the aluminum under the side with the starter.

Dale

 

Thank you very much!

 

If you want to make mounts, I've used isolastic bushes rather than urethane on a couple of sets, outlasts that stuff by far. Suppose one issue is, you lose the engine shearing out of the car in a prang with bolt through types - they're similar to TomU's one in that respect.

 

I'm using polyurethan windscreen adhesive, had no problems with that in a 6 year period in my other track car. Never heard of isolastic bushes though.

Did anybody thought about lowering the engine? I would assume lowering it at least 5mm would be necessary for it to not being higher than stock (stiffer poly mounts), don't you think?

 

***My experience is NOT with a FD, but a REW on a FC***

The REW engine on my FC sits about 3/4 inches lower than the factory 13BT. After many years, no issues, but here's a couple of things that might give you problems (like I experienced/noticed)

1 - Radiator hoses - You might have to custom make them, depending on how much you lower the engine

2 - Wastegate/Wastegate dump tube/Downpipe/Midpipe - Depending how much you lower it, you might have issues with the wategate hitting something on the frame or subframe, same with the wategate dump tube. Also, you might be putting the downpipe/midpipe in a bind

3 - Transmission angle - Maybe this one is not too big of an issue on the FD since the transmission mount is not bolted directly to the car's frame.

Hope that helps with your idea/question

BTW - Forgot about the oil crank case cover! In my case, it obviously sits lower, but its not the lowest part of the subframe.

 

My urethane mounts lower the motor probably a half inch as compared to stock. Mostly noticeable by looking at the R1 strut bar. It's not a problem. As long as everything fits you won't damage anything related to prop shaft or diff, not enough angle change for that.

Mounts aren't really an exact science. As long as you are relatively close it will be ok. Just go with what you like the fitment of.

 

I think today I found the reason for the difference in height between the 2 original rubber mounts, see attachement.

The aluminium mount and the cast iron one have a difference in height of that point, where the rubber mount sits, when you lay them flat on their mounting holes. Of course, this is no prove, because one of them could be tilted or just be mounted lower or higher, but its a good indication in that direction.

I tried to measure the difference, I would say ist 6-7mm, so that also corresponds to the difference in height I meassured at the OEM rubber mounts.

EDIT: ****. I just realized, thats exactly what can be read in TomU's thread. Maybe I should think about a brain rebuild aswell..

 

I bought solid aluminium mounts for my FD. They were from Super*now in japan, and they were 10mm lower than standard. No adverse effects yet, with 30,000 miles on them.

 

The rubber portion of the two stock mounts are different sizes because the arms themselves are different as well as the way the rubber is attached. The driver's side aluminum mount has the rubber case around it. The actual arm is thinner so the mount is slightly taller. The passenger side steel arm has the rubber portion bolted to it. The steel arm is thicker so the rubber is shorter. I recommend using two steel arms but I can cut you any length mounts you need.