Hi all,

I am replacing all of the grommets in my firewall since they are 50 years old.

I noticed the AC and heater core hoses use a single oval-shaped firewall grommet instead of individual ones for each hole. Is there a reason I shouldn't use standard circular grommets for the hoses instead of buying the bespoke oval ones for $46 from thezstore (this one)?

I found this picture of the firewall with the single oval grommet removed and it looks like 2 standard-fitting grommet holes. Any idea why they went with that ovular one? They must have used it for a reason I'd have thought, but I can't come up with a reason why using 2 circular grommets wouldn't work, no?.

Edited May 26May 26 by chaseincats

Maybe just to match the metal plate?

Here's one with slits so you don't have to open the lines to install.

Z Car Depot Inc

Air Conditioning A/C Lines Grommet on Firewall 260Z 280Z

Air Conditioning Lines Rubber Grommet on Firewall 260Z 280Z Reproduction air conditioning lines rubber grommet for the A/C lines going through the firewall. This grommet will work on cars equipped wit

1 hour ago, siteunseen said:

Maybe just to match the metal plate?

Here's one with slits so you don't have to open the lines to install.

Z Car Depot Inc

Air Conditioning A/C Lines Grommet on Firewall 260Z 280Z

Air Conditioning Lines Rubber Grommet on Firewall 260Z 280Z Reproduction air conditioning lines rubber grommet for the A/C lines going through the firewall. This grommet will work on cars equipped wit

Yep, cutting a slit in the oval grommet is definitely the way to go - thanks.

I was thinking about just using 2 circular grommets instead (from the generic grommet kit I have), unless that doesn’t jive with the firewall and that’s why Datsun used that odd oval grommet?

Edited May 26May 26 by chaseincats

The Nissan grommets I have are round and that hold down plate is flat on the top and bottom. Not sure how that would hold up? These are the ones I have left over. Someday I'll replace the old hardened ones on bottom of the hatch where it meets the slam panel, that's the plan anyhow.

On 5/25/2026 at 11:40 PM, chaseincats said:

Hi all,

I am replacing all of the grommets in my firewall since they are 50 years old.

I noticed the AC and heater core hoses use a single oval-shaped firewall grommet instead of individual ones for each hole. Is there a reason I shouldn't use standard circular grommets for the hoses instead of buying the bespoke oval ones for $46 from thezstore (this one)?

I found this picture of the firewall with the single oval grommet removed and it looks like 2 standard-fitting grommet holes. Any idea why they went with that ovular one? They must have used it for a reason I'd have thought, but I can't come up with a reason why using 2 circular grommets wouldn't work, no?.

Are the diameters different?

26 minutes ago, bpilati said:

Are the diameters different?

No, they’re identical