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Not sure how common of a mod this is, but I did it and I can't imagine I'm the only one.
A while back I decided that I wanted a 150 Mph speedo instead of my stock 110. It just looked cool. So I ordered an LT1 instrument cluster from eBay. Upon receiving it, I installed my super cool white faced - indiglow overlay and swapped out the factory V6 cluster. As I screwed in the final bolts in the dash, common sense hit me and said "This is a V8 cluster with a V8 tach, it won't work right on a V6". Sure enough it didn't. It read about 30% lower than the engine was actually running. And of course since we're talking about percentages the numeric difference was greater the higher the engine revved. Meaning that at 2000 rpm the tach read roughly 1400 rpm (600 rpm difference) while at 4000 rpm the tack read roughly 2800 rpm (1200 rpm difference). This can be detremental to your engines health. Thankfully I was aware of the issue and no damange insued.
Now I finally got around to fixing this and figured I would share my findings. The modification to the V8 instrument cluster is rather simple. All you have to do is swap out a 1500 pF capacitor with a 2200 pF capacitor. If you know your way around a soldering iron, short of removing and reinstalling the cluster this mod should only take about 10 mins.
You'll need:
- Decent soldering iron with fine tip (radio shack sells them relatively cheap)
- Solder (I used Radio Shack .015 diameter High-Tech Silver-Bearing Solder)
- Desoldering wick and/or pump is highly recommended
- Soldering Flux (paste is easier to work with but liquid works too)
- Needle nose pliers
- Razor blade and/or jewlers flat head screwdriver
- Vise
On the V8 Cluster
1.) Once you have the cluster removed from the car, you'll need to remove the circuit board from the assembly. It's held in by (7) torx/hex bolts. Don't forget to disconnect the Odometer motor when pulling the board away from the assembly.
2.) Locate the Tach section of the board.
3.) In the Tach section you will see 2 integrated circuits a black on and a mostly white one. The black one is a frequency to voltage converter, this is the chip that takes the tach signal and converts it to a voltage that controls the actual tachometer gauge. The mostly white one is a resistor network. Between the two chips you will see a yellow ceramic capacitor labeled on the circuit board as C6. There is writing two sides of this capacitor on side should say something to the effect of K5G 152J. If you look at the same capacitor on your V6 cluster it should say something like K5G 222K.
FYI: On a capacitor that has 3 numbers and a letter the first two numbers are the numeric values of the capacitor, the third is the multiplier, the letter is the tolerance. IE 222K = 2200 pF 20% tol, 152J = 1500 pF 5% tol.
Moving on...
4.) Desolder the 1500 pF capacitor from the V8 tach and pitch, we won't need it.
Note: When the capacitor was soldered in at the factor they bent the leads over and soldered them in place. This is where the razor blade and/or jewlers flat head screwdriver come in. You'll need to pry the leads straight again. Be carefull not to burn or cut your self. It helps to use a vise to hold the board.
5.) Desolder the 2200 pF capacitor from the same spot on the V6 tach and resolder it in place of the of the 1500 pF capacitor we threw away on the V8 tach. I recommend using solder flux - it's not absolutely necessary but it will aid in preventing a cold solder joint.
If you don't have your V6 cluster any more you can order the capacitor from Jameco
6.) Reassemble the cluster and reinstall it in the car.
Your tach should work properly now.
A while back I decided that I wanted a 150 Mph speedo instead of my stock 110. It just looked cool. So I ordered an LT1 instrument cluster from eBay. Upon receiving it, I installed my super cool white faced - indiglow overlay and swapped out the factory V6 cluster. As I screwed in the final bolts in the dash, common sense hit me and said "This is a V8 cluster with a V8 tach, it won't work right on a V6". Sure enough it didn't. It read about 30% lower than the engine was actually running. And of course since we're talking about percentages the numeric difference was greater the higher the engine revved. Meaning that at 2000 rpm the tach read roughly 1400 rpm (600 rpm difference) while at 4000 rpm the tack read roughly 2800 rpm (1200 rpm difference). This can be detremental to your engines health. Thankfully I was aware of the issue and no damange insued.
Now I finally got around to fixing this and figured I would share my findings. The modification to the V8 instrument cluster is rather simple. All you have to do is swap out a 1500 pF capacitor with a 2200 pF capacitor. If you know your way around a soldering iron, short of removing and reinstalling the cluster this mod should only take about 10 mins.
You'll need:
- Decent soldering iron with fine tip (radio shack sells them relatively cheap)
- Solder (I used Radio Shack .015 diameter High-Tech Silver-Bearing Solder)
- Desoldering wick and/or pump is highly recommended
- Soldering Flux (paste is easier to work with but liquid works too)
- Needle nose pliers
- Razor blade and/or jewlers flat head screwdriver
- Vise
On the V8 Cluster
1.) Once you have the cluster removed from the car, you'll need to remove the circuit board from the assembly. It's held in by (7) torx/hex bolts. Don't forget to disconnect the Odometer motor when pulling the board away from the assembly.
2.) Locate the Tach section of the board.
3.) In the Tach section you will see 2 integrated circuits a black on and a mostly white one. The black one is a frequency to voltage converter, this is the chip that takes the tach signal and converts it to a voltage that controls the actual tachometer gauge. The mostly white one is a resistor network. Between the two chips you will see a yellow ceramic capacitor labeled on the circuit board as C6. There is writing two sides of this capacitor on side should say something to the effect of K5G 152J. If you look at the same capacitor on your V6 cluster it should say something like K5G 222K.
FYI: On a capacitor that has 3 numbers and a letter the first two numbers are the numeric values of the capacitor, the third is the multiplier, the letter is the tolerance. IE 222K = 2200 pF 20% tol, 152J = 1500 pF 5% tol.
Moving on...
4.) Desolder the 1500 pF capacitor from the V8 tach and pitch, we won't need it.
Note: When the capacitor was soldered in at the factor they bent the leads over and soldered them in place. This is where the razor blade and/or jewlers flat head screwdriver come in. You'll need to pry the leads straight again. Be carefull not to burn or cut your self. It helps to use a vise to hold the board.
5.) Desolder the 2200 pF capacitor from the same spot on the V6 tach and resolder it in place of the of the 1500 pF capacitor we threw away on the V8 tach. I recommend using solder flux - it's not absolutely necessary but it will aid in preventing a cold solder joint.
If you don't have your V6 cluster any more you can order the capacitor from Jameco
6.) Reassemble the cluster and reinstall it in the car.
Your tach should work properly now.
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