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Old 05-08-2006, 08:29 PM   #1
hawaiianblue72
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Tach on 250 6

I just got a tach conversion kit from LMC. On the box it says V8 s only. does this mean it won't work on my 250 straight 6. it didn't say that it won't work in the catalog.???????
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Old 05-08-2006, 08:51 PM   #2
Palf70Step
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Re: Tach on 250 6

The tachs are different between the two internally, what the difference is I am not quite sure. A V8 tach wiill give you the incorrct RPM readings.
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Old 05-08-2006, 08:51 PM   #3
shelby987
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Re: Tach on 250 6

I actually just did this install on my 250, I pulled my tach apart and there was a switch behind the housing that allowed you to select 8, 6, or 4 cylinders.....but if the packaging specifically states V8 only, you might not have that option, but it might be worth a look.
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Old 05-09-2006, 12:32 AM   #4
72armyswbtruck
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Re: Tach on 250 6

These are really expensive if you find a v-6 tach, especially an original one
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Old 05-09-2006, 01:43 AM   #5
Bob B.
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Re: Tach on 250 6

Quote:
Originally Posted by shelby987
I actually just did this install on my 250, I pulled my tach apart and there was a switch behind the housing that allowed you to select 8, 6, or 4 cylinders.....but if the packaging specifically states V8 only, you might not have that option, but it might be worth a look.
Were you using a reproduction tach.? I think the V-6 tach. only read to 4000 r.p.m., and many of the V-6 tach.'s were mechanical.
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Last edited by Bob B.; 05-09-2006 at 01:44 AM.
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Old 05-09-2006, 01:59 AM   #6
Paul M
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Re: Tach on 250 6

hmm..i dont have my tach hooked up yet,and it was a v6 original one...guess it may not work with the 8 in there now.maybe if thats the case,we can trade?..lets see what everyone thinks
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Old 05-09-2006, 03:10 AM   #7
72armyswbtruck
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Re: Tach on 250 6

As far as I know the original v-6 tach and the original v-8 tach were not interchangable for some reason, but what I do know for sure is that your v-6 tach is extremely rare and hard to come by
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Old 05-09-2006, 04:07 AM   #8
Bob B.
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Re: Tach on 250 6

The 1968 GMC parts book says that there was one tach. for V-8's, part# 6468228, and one electric tach. for all 6 cylinders, part# 6468321. That one works on both 250 straight 6's and 305 and 351 V-6's. There was also a mechanical tach. for the V-6's. The V-6 has a tach. drive off the back of the camshaft.
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Old 05-09-2006, 10:39 AM   #9
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Re: Tach on 250 6

ahh i see...mine is looking like the electrical tach...since i have a long heavy single wire coming out of the firewall to where it was hooked up to the coil
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