My ‘73 has the 8.5” booster rather than the 7” one. I have a rebuilt one on its way but I can’t find a gasket to go between it and the firewall. I’m wondering if they ditched this gasket on the bigger boosters, or if it’s just NLA. The gasket for the 7” is readily available.

What are people using if I can't find one to buy?

1 hour ago, Matthew Abate said:

My ‘73 has the 8.5” booster rather than the 7” one. I have a rebuilt one on its way but I can’t find a gasket to go between it and the firewall. I’m wondering if they ditched this gasket on the bigger boosters, or if it’s just NLA. The gasket for the 7” is readily available.

What are people using if I can't find one to buy?

Does your '73 have the holes in the firewall for the 8.5" or the 7" bolt pattern (they are different)? 

1 hour ago, texasz said:

Does your '73 have the holes in the firewall for the 8.5" or the 7" bolt pattern (they are different)? 

8.5”

It’s a July car so it has a few 260z things happening here and there.

7 hours ago, Matthew Abate said:

8.5”

It’s a July car so it has a few 260z things happening here and there.

Ah I see.  I'm not sure who may have that or if it exists.  I'm guessing you have checked the usual suspects...

 

https://www.zzxdatsun.com/catRubber.php

https://vintagerubber.com/datsun-nissan/240-z/

https://www.totalzparts.com/product-category/datsun/240z-260z-280z/

https://www.datsun-garage.com/

https://zcardepot.com/collections/weatherstripping

https://zcarsource.com/rubber-pieces-kit-240z-260z-70-74-new/

https://www.thezstore.com/page/TZS/CTGY/classic03a14

https://jdm-car-parts.com/collections/weather-strip-seal-rubber-nissan-datsun-fairlady-z-240z-260z-280z-280zx?page=2

https://www.zeddsaver.com/collections/rubber

https://www.datsunparts.com/Rubber-Parts

http://www.new-datsun-parts.com/datsun-240Z-parts-rubber2.html

 

You may also check with https://www.240zrubberparts.com/ though I did not see one on his site it may be worth asking as he may be able/willing to make them.  Short of all that you could always buy a sheet of rubber and cut your own.

 

I hope something here helps you.

 

There are a couple of places you listed that I haven’t looked yet, but I have no idea if it is something that I Chili’s be able to find. I can’t find it in the FSM or the exploded diagrams of the booster.

I can’t imagine it doesn’t have one. The boosters aren’t that different. I am guessing I’ll need to make one if I can’t find it on one of these sites.

Anyone with a 260 or 280 that knows about these boosters?

My 78 280 had a very light silicone based adhesive on the back of the booster when it was installed. I also was expecting a gasket.

I just put an 8.5" in my 240Z and did not see any real differences between it and the original 7" except for the obvious size difference and bolt pattern.  I did not want to modify my Z so the mounting studs on the 8.5" booster were cut off and the adapter mounting plate from Z Car Depot was welded on, this also allowed me to use the rubber gasket for the 7" booster.

1978 and 1973 show no signs of a gasket.  My 76 didn't have one.  And carpartsmanual doesn't show one.  I think the rubber bellows is the seal between inside and outside.  No need for a gasket.  For what it's worth.

Where is the 7" booster gasket available from?

http://www.carpartsmanual.com/datsun/Z-1969-1978/brake/master-vac-hose

The 7” is at ZCar Depot and several of the other places listed above. I’m thinking I either don’t need one or should use a liquid gasket.

I have vague memories of this coming up before.  I think we decided that a person should seal the top and sides but leave the bottom open, so that if any water/condensation does get in there it can drain out and dry out.  Kind of like a window in a house.  The rubber bellows seals the hole to the inside so the gasket's only purpose is to keep stuff out of the gap,

13 hours ago, Zed Head said:

I have vague memories of this coming up before.  I think we decided that a person should seal the top and sides but leave the bottom open, so that if any water/condensation does get in there it can drain out and dry out.  Kind of like a window in a house. 

Ya know, for some reason that does sound familiar now that you mention it.

 

By the way, I got my gasket at Z Car Depot.

https://zcardepot.com/products/power-brake-booster-gasket-240z-70-73?_pos=1&_sid=a87c129e3&_ss=r

And it worked great on my new 8.5" booster for my 240Z with this adapter (the one I mentioned above).

https://zcardepot.com/products/power-brake-booster-7-240z-70-73-new?variant=29688152359025&currency=USD&utm_source=google&utm_medium=cpc&utm_campaign=google+shopping&gclid=Cj0KCQiA0MD_BRCTARIsADXoopa0Kt5nGMc-Hi_GfRzjOkysLppxy9-0NLqie2PblZqFrMIS1kUwYOgaAr3dEALw_wcB

Looks like they saw a need and filled it.  I don't think Nissan uses rubber gaskets.