Tach on 250 6 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

hawaiianblue72 · 05-08-2006, 08:29 PM

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.???????

**Palf70Step** · 05-08-2006, 08:51 PM

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.

shelby987 · 05-08-2006, 08:51 PM

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.

**Bob B.** · 05-09-2006, 01:43 AM

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.

72armyswbtruck · 05-09-2006, 12:32 AM

These are really expensive if you find a v-6 tach, especially an original one

Paul M · 05-09-2006, 01:59 AM

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

72armyswbtruck · 05-09-2006, 03:10 AM

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

**Bob B.** · 05-09-2006, 04:07 AM

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.

Paul M · 05-09-2006, 10:39 AM

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

05-08-2006, 08:29 PM	#1
hawaiianblue72 Registered User Join Date: Apr 2006 Location: Cuba, IL Posts: 68	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.???????

05-08-2006, 08:51 PM	#2
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,216	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. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God!

05-08-2006, 08:51 PM	#3
shelby987 Registered User Join Date: Mar 2005 Location: Just outside Durham, NC Posts: 894	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. __________________ 1969 SS 350 Camaro Sold 2008 1970 3/4T K20, stock height with 33's, 250 I6, 3 on the tree, and locked front and rear 4.10's 1980 Chevy Malibu 2 dr Sold 2007 1993 Olds. Cutlass Ciera Wagon Traded 2006 2003 Saturn L200 w/5pd. D/D My list spans 5 decades with One common thread.....GM!

05-09-2006, 12:32 AM	#5
72armyswbtruck Registered User Join Date: Feb 2004 Location: Idaho Posts: 4,033	Re: Tach on 250 6 These are really expensive if you find a v-6 tach, especially an original one __________________ "Remember, They can Kill You, but they can't eat You, That's against the law!!!!!!!!!"

05-09-2006, 01:59 AM	#6
Paul M Junior Member Join Date: Jun 2000 Location: Oakridge, Oregon Posts: 138	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

05-09-2006, 03:10 AM	#7
72armyswbtruck Registered User Join Date: Feb 2004 Location: Idaho Posts: 4,033	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 __________________ "Remember, They can Kill You, but they can't eat You, That's against the law!!!!!!!!!"

05-09-2006, 04:07 AM	#8
Bob B. Senior Member Join Date: Aug 2005 Location: Los Angeles Posts: 1,363	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. __________________ 1967 GMC CM-2500 Camper Cruiser, 351E V-6, NP 435 4 speed, Dana 60, and factory A/C. 2012 GMC K-3500 WT regular cab, 6.0L Vortec, 6L90.

05-09-2006, 10:39 AM	#9
Paul M Junior Member Join Date: Jun 2000 Location: Oakridge, Oregon Posts: 138	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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