Hi guys and gals,
I'm in the garage now hooking up my tach/clock and on hold for this info.This is the reason for the asap.

Where does the shielded cable for the tach pass thru the firewall for a clean factory looking install?

1971 cutlass S

thanks,
Walter

 

There is a 1.5 inch or so grommet with 3 holes between the brake booster and drivers fender - kind of tucked under there. It is the same grommet that the heavy gauge power wire goes through to the horn relay for power top and power windows. It may not have anything there if you do not have those options, but grommet should still be there - might be covered with a glop of black sealant.

 

Thank you for the fast reply.

I went out there and looked around,felt around, from top of car and bottom and cannot find any sort of grommet in that area.

My car is a hardtop and never had power windows,is it possible the hole was never placed there and filled with a grommet?

The closest grommet I can find to the area described is where the speedometer cable passes thru.This isn't what your talking about,is it?

thanks,
Walter

 

Do you have the assembly manual for 1970? It is on page 371 or 158 depending on how yours is numbered in Section 12. If not, I can scan and send it to your e-mail if you want.

It looks like your care should have it - just above where the fuse box penetrates thru on engine side- above this and towards the fender.

 

You might actually have to reach under the fender to see it.

It is definitely not where the speedo cable comes through.

 

If you have no power options, you may have a plug in the firewall with no holes in it.

 

That could be, but the assembly manual page shows the routing of the tach wire through an existing grommet. I mean, it does not appear to say you need to use a special grommet, it implies it is already there, but maybe there is a solid plug there and you add the 3 hole plug if you have tach or power options. I know my Chevelle hardtop had no power options and I added power windows and that grommet was already there hiding under some goop the factory must have put there.

Maybe there is a solid grommet as the previous poster said, but there should definitely be a 1.5 inch or so hole drilled in the metal there - it is not something that the assembly manual shows that you need to drill if adding a power option or tach.

Also - I have a couple spare grommets like that with the 3 holes if you need one.

 

Well, there may be more variability than first thought. I checked my 1970 and it had the hole where oldsconv described. Then I checked both a 1971 non-AC stripped down car (it even had a radio delete!) and the only hole I could find was just above the heater box. I also checked a 1972 Cutlass S and found only one hole with a grommet right above the transmission tunnel. Here's pictures of the 1972 first, then the 1971.

P1010001-3.jpg

P1010002-3.jpg


P1010003-2.jpg

P1010004.jpg

P1010005-1.jpg

 

Thanks to all 3 of you guys for your fast replies,and pics too!

I ended up getting sidetracked and going to where I have some stuff stored and picked up my 1972 assembly manual. Found a page where it says a hole for grommet needs to be cut.
Also found an old pic of my firewall before I cleaned and painted.Shows my firewall hasn't been cut for the grommet mentioned.
Maybe I'll consider cutting the hole and installing a grommet.
thanks much.

DSC03772.jpg

DSC02506-1.jpg

 

Ok. Thats interesting. I guess I assumed 70-72 would all be the same. I guess for 71-72 the factory drilled that hole only when needed. There should be a locating dimple for it and you can run a hole saw if enough clearance. Just don't chew anything up when you break into the inside.

 

I'll have to map out a plan for drilling as far as clearance and location of the grommet.

Pm sent about your extra grommet Oldsconv. thank you

 

Oldsconv,

It was the same way in 1970 as in 71-72, meaning the hole and grommet only got put there on the assembly line if the car needed it. I've got a 70 with no hole or grommet. It's also a good way to tell if the car came from the factory with a Rally Pak or not. No hole.....no Rally pak. Another way to tell on a 70 is to look for the little clip that holds the Tac wire to the firewall. On cars with a voltage regulator the clip would attach to the lower bolt.....but 70 442 and W's had an internal regulator in the alternator. So they had to drill that one hole in the firewall to hold the clip. So for 442s and W's....no hole and clip on the firewall.......no Rally Pak. The assembly manual shows all the dimples on the firewall and what goes with them. Interesting stuff.

later,
bob

 

The accessory grommet can be seen here on the side of the booster...


Cars with cruise control certainly got it.

 

Yeah Rob, I didn't mean to imply the hole and accessory grommet were only installed for the Rally Pak.....lots of options requried it.

regards,
bob

 

I did not know it was installed only for the rally pac... Big hole for such a little wire!
Was the 3 holer grommet used or just a single hole? Yes, this IS interesting stuff to know...

 

Hi Rob,

Yeah, this is interesting stuff. My 72W has very few options, but it does have a Rally Pak.......and the accessory grommet with only the braided tach wire running thru it. When I bought my 70W it had the Rally Pak portion for the gauges installed in the dash, but no tach. Instead someone installed a Sun Super Tach on the steering column. I just assumed it was an original Rally Pak car and someone pulled the tach/clock and installed the Sun tach because it's too hard to read the Rally tach. This year when I finally got around to paying some attention to the car I stared digging for Rally Pak info and have found out that my car never had a Rally Pak from the factory.

Someone simply installed the Rally Pak gauge pod and replaced the senders on the motor with the proper ones for gauges. I know this because I don't have the accessory grommet (or hole for one) in the firewall, there is no braided wire anywhere to be found, and there is no hole in the firewall for the clip and screw to hold the braided wire.

I'm sure lots of options would have required using the accessory grommet, not just the Rally Pak....but that grommet only has 3 holes.....so I'm guessing only 3 things can go thru it. I checked and all the repop places (Fusick, Inline, etc) make the correct grommet. Like you said.....interesting stuff.

regards,
bob

 

Great info you guys have added to this thread,hopefully it will come in handy for others future reference.

thanks