M52 in an 86 325 swap & tach doesn't work?

[ForcedFirebird]

I'm not trying to create any debate. My biggest problem is the confusion of one says this and another says that. I am trying to pick out what will work for my car. All of them (each year) have their little differences.

I appreciate each and every response. I realize any item in the line of things that make these work can ruin the whole attempt. So all have input but likely only one combo will work in my particular car. I have to try some of the suggestions until things begin to move.

Again, Thanks to all !

Debate?

I have the same car as you, dude. I had to wire the tach in the glove box, just as I suggested, and I went to a 7k tach, as you will need to do too.

[tn325i]

Debate?

Slightly, as in- do it this way!.... No do that !... You don't need to.... Yes you do....

I have the same car as you, dude. I had to wire the tach in the glove box, just as I suggested, and I went to a 7k tach, as you will need to do too.

Working on it man... Thanks...

[joecassie]

i just did it yesterday and now my rpms are right so im not worng nor am i giving out bad information

[tn325i]

Never said any one was wrong. Just have to figure out what works in my car.. It has been thru many changes during my ownership.

[ForcedFirebird]

i just did it yesterday and now my rpms are right so im not worng nor am i giving out bad information

This thread is about a 24v in an early model 325. NOTHING has to be done for the tach to read proper as long as it's getting signal from the DME. If you started with a 318, then yes, IF you have a coding plug, it needs to be changed and if you have a chip in the cluster vs a coding plug, you need to change the whole cluster. Period the end without a doubt. A 6cyl tach reads 6cyls weather it be a 24v or a 12v since the spark event is happening every 120 degrees of crank rotation. A 4 cyl is reading an event every 180 degrees of crank rotation and the way your tach interprets this info is what you see the needle reading. This is why a 4cyl tach will read higher than the actual engine speed, it's thinking a signal is coming in every 180 degrees when it's actually coming in every 120.

Maybe you change the coding plug in YOUR car yesterday, but that has nothing to do with the OP's issue. The 1986 325 (e, es, i or is) tach will read the 24v RPM output, it's just the eta tach won't go past 5500rpm. The 7k tach will read just like it would with an m20 so long as it's getting signal.

[tn325i]

I have had the 7k tach for a while. I was running a m20 stroker before. Tach worked fine with the M20 I removed so I now think it has to be an issue from the dme signal.

Next bit of time I get I will trace the wires...

[RobertK]

Steve, I have a couple I clusters laying around (all late model) so if you can use a whole cluster let me know.

[tn325i]

I think I figured out the tach issue. Will let you know if it is working later.

Thanks Robert, I think I may have it licked.. Gonna retrace some solder joints tonight and see if I can make it work. Everything else is as it should be.

[firaspop]

Hey, I’m doing the same wiring and my tach jumps to about 0.5 when the car is idling and when I accelerate it goes up in really small increments, it’s reading way less than it’s supposed to