70 Tachometer Firewall Grommet

[Clark E.]

It's said no question is a dumb question so here goes...I have a new 4 hole grommet from Paragon that requires drilling out the plugs to run the various tubes, cables, hoses, etc. through. The end fittings on the tach cable are considerably larger than the hole for the cable and the thickness of the grommet won't allow it to stretch enough for the fitting to pass through. Short of cutting the side of the grommet, any suggestions on how to run the cable through the grommet? Thanks...Clark

[Alan S.]

Re: 70 Tachometer Firewall Grommet

Hi Clark,
It may be a sacrilege but using a very sharp blade to split the sides of holes in the grommets does make getting the tach cable and back-up light connecter through the holes much easier.
When you push the grommet in place the firewall holds the splits completely closed. Then, if you're a little generous with the sealer, (as St.Louis often was), on the grommet, the splits can't be seen even if looked for in particular.
Regards,
Alan

I've read that the grommet can softened enough in hot water to get the tach cable fitting through the hole, but I didn't have any success doing that.

[Clark E.]

Re: 70 Tachometer Firewall Grommet

Thanks Alan...Slitting the grommet supports what I was thinking but it's good to have it validated.

On the left top of the firewall there are 3 holes for passing connectors through to the interior. facing the car, the one on the right is the hole we're talking about for the tach cable, oil tube, backup lights and the washer vacuum hose. The one immediately to its left I believe is for the speedo cable. Not sure what the hole directly below it is for and the AM isn't clear. It looks slightly smaller than the other two and would take a single line. Any help would be appreciated...Clark

[Alan S.]

Re: 70 Tachometer Firewall Grommet

Hi Clark,
On my 71 the hole to the LEFT of the 4 hole grommet has a 3 hole grommet for 3 vacuum lines.... 1 is the vacuum supply to the various dash controls, and 2 are coming back out from the dash on the way to the headlight relay and wiper door relay.
The hole BELOW the 4 hole grommet has a grommet with a single hole in it for the speedometer cable. The grommet is quite unlike the other 2 (the 3&4 hole) in that it's relatively thin and has 3 metal tabs that help hold it in place. The grommet is in a part of the firewall that's turned on a slight angle so that the cable is headed in the direction it needs to be in order to get to the transmission without a kink developing.
I hope this helps!
Regards,
Alan

[Clark E.]

Re: 70 Tachometer Firewall Grommet

Again, many thanks Alan...I had the tach and vacuum lines firewall holes reversed and it makes sense that the speedo cable would be in the lower, smaller hole. I had the thin, three tab grommet w/ the speedo cable fitting through the larger hole and it was obviously not correct as it didn't fit.

I was a member of Mason Dixon some 20 years ago and attended a judging in Havre de Grace last Spring at the Chevy dealership. I didn't see an upcoming judging in the Driveline but would like to have mine judged in 2013 if the club has one scheduled. I live in Grasonville. Thanks...Clark

[Alan S.]

Re: 70 Tachometer Firewall Grommet

Hi Clark,
The Mason Dixon Chapter has a small event planned for the the end of October in Pikesville, and I would think the Spring Meet will be in Havre de Grace next Spring.
You can check the Mason Dixon calendar or p.m. Rick Aleshire, the M-D Judging Chairman. He frequents this Board so he'll see your message.
It would be great to see you at a meet!
Regards,
Alan