I've undertaken an interior restoration and taking it as far as I can based on my skills.  Starting with the rear I stripped it all down to the bare metal, did my por 15 and repaint, and am now ready to put the sound deadener back.  I chose kilmat 100 for a decent price to performance ratio before I really got into this effort.  After I've painted the bare metal it looks so nice I'm almost hesitant to put the shiny stuff down rather than something more original I could paint.  While I struggle with that decision lol, I'm wondering if I can get some opinions on where to put the new stuff in the deck area.  I've already decided the original location a must plus the vapor tank and antenna areas before I put those items back in.  Now on to the rest, do you guys advise putting under the vinyl on the wheel wells and shock tower?  In the spare tire well, along the side near the quarter panel windows, etc?  I realize the more I do the more weight I add but this isn't really a racer and all these other spots are mostly hidden other than the tire well so only I'd know (but then again i'd know lol).

I used the brand Canopus from amazon with great success about 2 months ago. I used the black color instead of the aluminum color. I did install it ever where possible even in the spare tire well. I removed the vapor tank and install it in that side, the antenna side and also the hole rear deck. I did remove the seats and covered the whole floorboard, drivers and passenger. what a difference in the ride and maybe I added 30lbs. no big deal for the weight, for the way the car rides. I am going to do the riser panel behind the seats and as much of the doors as I can, and I will stop there. maybe at the end game I added 35-40 lbs tops. it was worth it for the quiet ride. it is a must do project.

I used SilentCoat MLV with the silver backing. Watch yourself as the edges can get razor sharp.

I didn’t go for the full coverage as some do as it’s overkill and adds too much weight. But, what I did find made a massive difference were:

1. Trans tunnel - fully covered. I feel a lot less heat coming off there now during and after a good blast.

2. Footwells - on those I went MLV where the original insulation would have been with 3mm self adhesive closed cell foam over the top

3. 1x piece Slap in the middle of the door skins and 3mm closed cell foam between door cards and doors.

4. The panels behind the seats

5. The rear boot deck area and wheel well act like a giant speaker so the flat bits got covered 70% and the wheel well about 50% - the wheel well may be worth fully covering for aesthetic reasons. Then overlaid with loose (not glued down) 25mm closed cell foam under the deck carpet.

6. Strut towers got MLV

7. Rear wings got a half or 3/4 piece each.

8. Oh and a couple of pieces of MLV on the fire wall - especially important on the exhaust side.

BIG BIG difference when shutting doors or cruising. A lot less wind and road noise as the door skins etc don’t vibrate the same way anymore. Totally worth the little weight penalty. But certain areas like the strut towers and trans tunnel benefit from full coverage. It also helps the vinyl sit flatter.

You need earphones to hear the difference but here’s a video I did for a friend:

The panels without it rang like a bell.

Trouble is, now I hear the transmission whining and all manner of other stuff I couldn’t hear before :p

Thanks guys.  So adding it under the vinyl on the towers didn't affect the placement of the vinyl?  No issues with it not sitting right after adding?  I'm open to adding it where it makes sense and will do as much as i possibly can.  Oh and the wheel well, having a full size tire in there doesnt dampen the sound?  I can see when empty its a serious resonator, but all that weight and it being rubber no less doesn't do the job?

It was fine on mine but I have a European ‘77 260z with different vinyl to the 240 so I can’t say it will be fine for yours.

Best to measure the MLV you use (I.e. 5mm thick or 3mm) then use something of the same thickness like say cardboard and try to put your vinyl over it to see if it causes issues.

If you don’t do the strut towers it’s bit the end of the world.

I don’t carry a spare wheel, just a can of puff and a pump and use the space for things like spares, jump leads etc. So for me it did resonate but your point is valid. Also my spare used to fit so tight that I’m not sure it would fit now without delating it.