Grand Prix tach swap how to

[G-Body_Vet]

It comes out of a small grommet on the firewall ...the grommet is left of center and about 6- 8" from the top of the firewall....I'm doing this by memory but I can take a run over to my car tomorrow to confirm it wit measurements if you need it...

found this...you'll see the brown wire from the tach filter going down and it goes through the firewall close to that location...

My car doesn't have a tach filter or grommet anywhere in that location. I only have two ground straps.

 

[Bonnewagon]

Wowsers, I think he's got it! It's white and in the correct location. That looks like the ignition switch harness. Probably a continuity test is in order, you don't want to fry a tach. If it's the same wire that is at the gauge harness then all you need do is add a connector that fits,(spade?) or cut it and use your own connector, or just solder a wire, and continue on to the distributor. Use a grommet in the firewall as Pontiacgp said his car has, and you will be factory correct. Oh, and I've yet to see a factory tach filter, but I've never had a factory tach equiped car either.

 

[G-Body_Vet]

Wowsers, I think he's got it! It's white and in the correct location. That looks like the ignition switch harness. Probably a continuity test is in order, you don't want to fry a tach. If it's the same wire that is at the gauge harness then all you need do is add a connector that fits,(spade?) or cut it and use your own connector, or just solder a wire, and continue on to the distributor. Use a grommet in the firewall as Pontiacgp said his car has, and you will be factory correct. Oh, and I've yet to see a factory tach filter, but I've never had a factory tach equiped car either.

As soon as I find out what the hell I did with my volt meter I'll post the results.

 

[Bonnewagon]

It's probably in the last place you used it. That's where I always find where I left my beer.

 

[G-Body_Vet]

It's probably in the last place you used it. That's where I always find where I left my beer.

I usually find empty bottles in my last place :lol:

Last time I needed it was when I went out on a limb using a '91 VW GTI for a work car about 3 years ago. The only way you could troubleshoot anything on it was with an ohm meter.

 

[deanlemans81]

Hey guya, This is a great info post for us pontiac owners! Thanks for all the detailed pictures.
Dean

 

[G-Body_Vet]

After having to go buy another multimeter I finally got out there and tested the wire vs the contact on the cluster plug. Looks like we have a winner!

 

[G-Body_Vet]

Since we hit a whopping 60 degrees today I figured I'd see if the tach actually worked. Since the 305 is coming out anyway, I just used some 10ga wire, a spade connector and a butt connector that I had laying around. I will get a proper tach wire when I install my 455 so everything looks pretty! Here's where I made the splice.

I'm not a fan of drilling unnecessary holes in sheet metal so I drilled a hole through the speedometer cable grommet just barely big enough to slide the wire through. The nice part about it was that I easily fed it through the firewall, all the way down to the floor without having to fish it out from behind the dash.

Here's a vid of it working (notice that beautimus custom steering wheel lol)

 

[pontiacgp]

nicely done and those silver gauges look real nice...that steering wheel looks great too, I'll have go to back the thread where you explained how you did it

 

[G-Body_Vet]

nicely done and those silver gauges look real nice...that steering wheel looks great too, I'll have go to back the thread where you explained how you did it

Thanks. It's actually nice when things turn out the way you want. That steering wheel is from a Riviera, don't know what year though. The GP emblem is a NOS, mid seventies GP hood ornament insert IIRC. Getting it to fit was just a matter of making the octagon shape round with a bench grinder. Luckily I took just enough off to make it a tight fit. There isn't even any adhesive on the back of it. The Riv emblem popped out pretty easy from the back of the horn button too.