question about Tach and number of Cyls

[RyansToy]

I read somewhere about instrument clusters, more specifically the tach (I assume) being for a 6cyl or 8 cyl? does that make sense?

Is there a difference between OE clusters for a 6 vs 8?

Wouldn't the tach signal just count cyl 1??

[EARNHARDT#3]

The cluster is mostly the same. The tach itself is indeed different. That's why on aftermarket tachs there's typically a switch for 4/6/8 cylinders.

To be more specific...if a 1cyl engine is running at 500rpm that cylinder fires 500 times. If a v8 is running at 500rpm each cylinder fires about 62 times per minute. For the tach it's crucial to have it set/made for a certain number of cylinders.

[RyansToy]

I guess I had assumed it was going to read off cyl 1 only. Then it would not matter.

[EARNHARDT#3]

Originally Posted by RyansToy

I guess I had assumed it was going to read off cyl 1 only. Then it would not matter.

Yes it would. The more cylinders the motor has the less frequent they fire per RPM. It doesn't matter if it's cylinder 1,3,5,6,8. They all fire the same amount of times per minute.

[Matt Cramer]

Originally Posted by RyansToy

I guess I had assumed it was going to read off cyl 1 only. Then it would not matter.

It wouldn't if it triggered off only one cylinder. But it's easier to pick up the signal at the coil terminal.

[swamp rat]

I forget what its called ( resistor???) but look at the back of the tach, there will be a little item held on by 2 nuts, there are different colors, red is one of them, i cant recall the others, if i recall correctly to change the tach from 6 to 8 or the other way all ya got to do is change out that colored part for the correct color.