tyler031734 Posted April 8, 2012 Share Posted April 8, 2012 The stock tack in my 78 was stuck at 1K from the PO. Then I did the SBC swap (6.6L) and the replacement tack I have barley moves off the bottom at idle and seams to be at least half of what it should be. I haven't mounted it in the dash yet. Just hooked it up standing over the engine bay. If I had the sporadic jumping around needle Id know what to do, but This has me a little confused. Quote Link to comment Share on other sites More sharing options...
GOTHALOSISM Posted April 9, 2012 Share Posted April 9, 2012 Not sure on yours but mine requires a reistor (still have to find the right one). Quote Link to comment Share on other sites More sharing options...
tyler031734 Posted April 9, 2012 Author Share Posted April 9, 2012 (edited) That resistor from my understanding is to stop the jumping around the needle might do from time to time. From my understanding V8's require you to "turn your tack down" because your tack see's 33% more spark than its used to (per RPM) from the factory inline 6. Mine's low from the get go. Totally backwards to what I have read. That resistor is some 15K Ohm I believe, or I maybe getting the internal regulator swap mixed up, but either way I don't see a resistor helping my issue. Anyone? Edited April 9, 2012 by tyler031734 Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 9, 2012 Share Posted April 9, 2012 What brand and model is the replacement tach? I had a Sun tach years ago that was adjustable for 4, 6 and 8 cylinders. Yours might have dip switches, jumpers, or a switch, internal or external. Pretty sure that there are external signal modifiers out there also, for using stock tachs with alternate engines. Quote Link to comment Share on other sites More sharing options...
tyler031734 Posted April 10, 2012 Author Share Posted April 10, 2012 What brand and model is the replacement tach? I had a Sun tach years ago that was adjustable for 4, 6 and 8 cylinders. Yours might have dip switches, jumpers, or a switch, internal or external. Pretty sure that there are external signal modifiers out there also, for using stock tachs with alternate engines. Stock 280z tack Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 10, 2012 Share Posted April 10, 2012 Isn't that covered in the Jags That Run book? Don't have it myself but I have to assume. Quote Link to comment Share on other sites More sharing options...
GOTHALOSISM Posted April 10, 2012 Share Posted April 10, 2012 http://forums.hybridz.org/index.php/topic/100157-hei-tac-issues/page__p__939215__hl__tach__fromsearch__1#entry939215 http://forums.hybridz.org/index.php/topic/100044-gm-hei-question/page__p__938197__hl__tach__fromsearch__1#entry938197 If you search you'll find more info, using the correct spelling will help as well. Remeber its Tach not Tack. Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 10, 2012 Share Posted April 10, 2012 (edited) Here's a "might work" - http://www.egauges.com/vdo_send.asp?Sender=Classic_Tach_Filter&Cart= Of course, it's probably just a resistor... Edited April 10, 2012 by NewZed Quote Link to comment Share on other sites More sharing options...
GOTHALOSISM Posted April 13, 2012 Share Posted April 13, 2012 (edited) Finally got mine fixed yesterday, it took two 4.7k reistors. Edited April 13, 2012 by GOTHALOSISM Quote Link to comment Share on other sites More sharing options...
tyler031734 Posted April 13, 2012 Author Share Posted April 13, 2012 (edited) I looked over those threads you posted. A bunch of useless info, but I did find something about the wire feeding the coil. Had to make sure I used a big enough wire. I have a 20 amp relay feeding it so no bottle neck there. I hooked the tach back up, and at about 3000 RPM it finally hits almost 1K on the tach. From what I have read. The resistors are only if your needle bounces around. Mines rock steady, just way way way to low. And GOTHALOSISM, you never stated what your problem was. Edited April 13, 2012 by tyler031734 Quote Link to comment Share on other sites More sharing options...
GOTHALOSISM Posted April 14, 2012 Share Posted April 14, 2012 The lt1 aka v8 has 8 cylinders, as we all know the stock enine is 6. With the 280z tach I have to gimmick it into thinking its a 8 with the resistors. I'm not sure how it is affected with a 240z tach though. Quote Link to comment Share on other sites More sharing options...
tyler031734 Posted April 15, 2012 Author Share Posted April 15, 2012 (edited) The lt1 aka v8 has 8 cylinders, as we all know the stock enine is 6. With the 280z tach I have to gimmick it into thinking its a 8 with the resistors. I'm not sure how it is affected with a 240z tach though. Yeah, I talked about that increase in post #3. Not sure where the 240z tach statement came from. I said '78 in the first post and in post #7 "stock 280z tach" And I believe you meant trick it into 6 cylinders... Edited April 15, 2012 by tyler031734 Quote Link to comment Share on other sites More sharing options...
GOTHALOSISM Posted April 15, 2012 Share Posted April 15, 2012 yup, sorry i was getting my threads confused. There is a thread like this on an lt1 website. Quote Link to comment Share on other sites More sharing options...
tyler031734 Posted April 15, 2012 Author Share Posted April 15, 2012 But that does brink up an interesting thought. Not that it pertains to my current issue. I read somewhere to turn one of the brass flat head knobs to adjust the tach to operate correctly and if the needle is jumpy to add a small resistor of about 15k ohms. but your method makes better sense. And 240z tachs will not work with EI as far as I know. That's why people gut 280z tachs to put in there 240z shells. Quote Link to comment Share on other sites More sharing options...
tyler031734 Posted April 15, 2012 Author Share Posted April 15, 2012 I went out and tried to "adjust" both of those brass screws. It feels like a mounting screw and not an adjuster. I did find another 280z tach on my shelf and tried it as well. Same issue. Im thinking I my have an HEI problem. Should make my dad laugh. He said he's only replaced one his whole life and that was just to rule it out as an issue. Quote Link to comment Share on other sites More sharing options...
tyler031734 Posted April 15, 2012 Author Share Posted April 15, 2012 (edited) New symptom, car dies when you hook the tach up! Wont start with it hooked up either. Took the plastic cap off to check connections and they all look good.... hmm, more hunting. EDIT: Replaced coil. $25 not bad. Car runs when tach is hooked up now. Properly grounded the tack case. Coil is getting 13.5v with a temporary test wire and still low readings. Revving as high as I like at a standstill. only putting out enough current for 600rpm Edited April 15, 2012 by tyler031734 Quote Link to comment Share on other sites More sharing options...
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