10 replies to this topic

[ferox]

I want to replace the two old crusty wires from the ignition coil to the disty pick-up coil in my '81 Hatch 4WD. Does the gauge of the wires matter and if so can someone tell me what they are? I don't have an FSM yet, but the Haynes says I have a "late Hitachi"...the kind with two 90 degree female spade connectors that plug onto the Pick-up Coil/Control Unit. Thanks

[GeneralDisorder]

16 guage.

You shouldn't have to replace them. Cut them back till you get good copper and put new ring terminals on. I suppose you can replace them if you really want to, but I've never seen a need for that.

GD

[MilesFox]

i have used speaker wire before and it worked, but i would recommend sticking to original gauge or do like general disorder suggested, as to not have problems with resistances and overdrawing the ignition module

[ferox]

Thanks for the info. I was running the 2WD disty for a while and just recently switched back to the Hitachi. I noticed some white crusty stuff (about the size of a pencil eraser) on the disty housing where the wires enter the disty interior. It was like the stuff that builds up on battery terminals. The rubber grommet is totally brittle, barely there, and going away fast, and while I was setting the timing I got shocked through my gloves while rotating the disty. The shock could have been from the high tension wire, but every now and then my idle speed drops really low ~400rpm, but when I get my timing light on it it's perfect. So it's episodic...not consistent. The ND Disty had a rock solid idle speed. What I think may be happening is that the 27 year old insulation on one of the ig. control wires may have a little crack in it that arcs to/from the disty housing. Since it's such a cheap and easy thing to replace I thought I'd just do it. The Hitachi disty is a reman that has about 2000 miles on it, but the wires are original. Any other thoughts on this would be welcome.

[ferox]

Well I adjusted my idle speed screw and the problem seems be to solved. I didn't realize that the two disty's would be that different at idle. I am guessing that is because of the steeper advance curve of the 2WD distributor.

[GeneralDisorder]

Well I adjusted my idle speed screw and the problem seems be to solved. I didn't realize that the two disty's would be that different at idle. I am guessing that is because of the steeper advance curve of the 2WD distributor.

The advance curve of the two are identical. That's a wives tale that has been perpetuated for an obscenely long time now. Also there is NO vacuum advance at idle. The vacuum supply is ported and doesn't exist when the throttle is closed. So distributor differences with respect to advance curves cannot affect idle at all. Idle timing is static.

Actually - I've found some evidence that different years/models (feedback vs. non) of the Hitachi have different spring rates for the vacuum advance pot. Right now I don't know the specifics of which models they came from as that's been lost to time and a long stay in my garage, but I have several examples awaiting testing in my shop - I'm going to map their exact advance curve.

GD

[ferox]

With all due respect GD, and I do mean that quite sincerely, when I started refurbishing my ea81 I bought the reman Hitachi, then I read Subiemech's write up on the 2WD disty. I got a good ND disty from the yard and threw it in, and I have to say it performed exactly the way Subiemech described. I've been running it for the past nine months, and the power advance was very much shifted to lower rpms. I only switched back to the Hitachi because I like the way it drives better. The differences are significant. Now I know you must have good reasons for saying they are exactly the same, and I have to check myself many times over before disagreeing with you, but I have direct observational experience that says the advance curves are different...in my car. My car is straight stock except for the emissions stuff being removed. If I am not mistaken you run a Weber or SPFI on your car(s), and I am wondering if the differences are neglegible on those systems. I am expecting you to totally disagree with me, but I was actually surprised as to how perfectly the performance of the two disty's correlated to what Subiemech described. It's easy to compare the two disty's in my car because it consistently runs great (due in large part to advice I have vicarious gleened from you over the past couple years), but unless you can tell me a different reason for the differences between the two (which I would honestly be very interested in), I am going to have to respectfully disagree based on direct experience.

[ferox]

So aside from the advance curve debate, which I am not going to claim a full understanding and would welcome further enlightenment, why would the Hitachi disty lower my idle speed so much? Does the Hitachi shaft rotate slower or something?

[GeneralDisorder]

I also have direct experience with both. Used on Hitachi's and Weber's over many years. I run the ND on my Weber'd rigs because the rotation of the plug wires on the cap better clears the choke.

I also JUST switched from a Hitachi to the ND on my hatch - while I rebuilt the Hitachi off it - no difference.

In the FSM there is only ONE advance curve for all vacuum advance's used - it has a graph of the curve in relation to RPM. I can scan it if you like.

I have lots of experience with lots of carbs. I've rebuilt, used, off-roaded, and streeted both distributors with both carbs, and can say that I've never found a single difference that could be attributed to the vacuum advance.

Now there might be differences between years - I would need more FSM's to know that for sure. Also some ND distributors with electronic pickup's were used on later 80's EA71's and may have a different curve. As I said I've also found different spring rates on different Hitachi vac cans. The point is that the situation is not as clear cut as "2WD vs. 4WD" - it has a lot to do with year and model as well. It's not clear that all ND's are different from all Hitachi's. The data collection to ascertain the exact differences is taking me years because this stuff is 25 years old.

You can disagree with hard evidence if you like, but a single experience does not indicate a trend. My experiences have been many, and varied, and I have not seen a consistent trend that is useful.

GD

[ferox]

OK the spring rate difference of the vac. can. makes sense to me. I didn't mean to be a contrarian, I just didn't understand how they could be so different yet not different. Thanks for explaining that.

[subaruguru]

the only problem i have ever had with a disty besides one blowing up (long story) is the coils NP coils work on NP distys NP coils DO NOT WORK on hitachi distys idk about the other way around. but i do know i spenta week trying to figur out why my car would not run only to come to the conclusion that i put the wrond disty in it.