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post #1 of 12 (permalink) Old Apr 16th, 12, 11:47 AM Thread Starter
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questions not answered

I asked this question a week ago and did not get a resonable response. I have a new blinker tach with about 1100 miles on it. Last week it started jumping from 2000 to 3000 rpm's no matter what the speed. It is fine at idle but any increase in rpm's it jumps to 2000 rpms and bounces back and forth.

Second question, I need to figure out what bellhousing I have and can not find numbers on the top, would you kow where they would be?
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post #2 of 12 (permalink) Old Apr 16th, 12, 12:13 PM
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Re: questions not answered

Can't help much with the Tach... Check your connections, make sure they're tight. If nothing else, swap it into another car to see if the problem persists.

Look on the right/passenger side of the Bellhousing, if it's original GM that's where it will be cast.

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post #3 of 12 (permalink) Old Apr 16th, 12, 9:30 PM
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Re: questions not answered

I had same problem with column mounted tach and when I changed dash to tach dash, same problem, only thing that was the same is the distributer, I just havent changed the coil yet to see if it solves the problem, it's an HEI.
Dont know about bell

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post #4 of 12 (permalink) Old Apr 17th, 12, 7:38 AM Thread Starter
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Re: questions not answered

I do have an hei distributor and the weird thing is about two weeks ago the module went out in the distributor and the tach problem ay have started then but not sure. I am going to replace module, rotor and cap today to see if that fixes the tach, if not Muscle Factory said send it back and they will send me a new one, pretty good on there part seeing it is over a year old. Will let you know tonight what happens.
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post #5 of 12 (permalink) Old Apr 17th, 12, 8:26 PM
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Mac
 
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Re: questions not answered

Thanks Nailer, mine has done this since it was new, it'a an accel hei, idle is fine and above 2700 also, bbut in between it jumps around, engine runs fine, dist is about 2 years old. Let us know what happens!

1970 Chevelle SS full weight street car (4030lbs)
498-11.5:1 (Mac built) 91 pump gas+
Strauby sissy roller -
brodix-rr rec 294
weiand stelth- Pro Systems 1000
turbo 400 10" 3200 Coan 4.10 12 bolt
Best Passes on28-10.5-15 slicks and 110
1.5568-7.0061-98.25
1.6194-11.1666-120.94

If it wasn't dangerous, it wouldn't be fun!

http://www.chevelles.com/showroom/data/507/IMG_2519.JPG
http://www.chevelles.com/showroom/da.../IMG_24851.JPG
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post #6 of 12 (permalink) Old Apr 17th, 12, 8:43 PM
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Re: questions not answered

nailer,
Make sure you have the tach grounded directly to the engine block. Not to the firewall with a sheet metal screw, not to a dash brace . . . . directly to a good clean, no paint ground on the engine block.

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post #7 of 12 (permalink) Old Apr 17th, 12, 9:18 PM Thread Starter
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Re: questions not answered

thanks Bill will let everyone know what happens
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post #8 of 12 (permalink) Old Apr 19th, 12, 8:22 PM Thread Starter
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Re: questions not answered

OK replaced the module and the coil and no change in the tach so the tach is coming out and going back to seller. Any tips on removing the tach or is it going to suck as much as I think?
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post #9 of 12 (permalink) Old Apr 21st, 12, 12:33 PM
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Re: questions not answered

Put a BB distributor with the points and original style coil in. Tack will probably work. Then you know it's not the tack; but the HEI ignition system.
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post #10 of 12 (permalink) Old Apr 22nd, 12, 7:05 PM Thread Starter
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blinker tach

checked all the ground straps and everything looks fine. going to take it to a speed shop on Tuesday but have a question. How does the signal make the tach work. Is it from the rotation of the rotor? I have replace everything in the HEI with new except for the cap. The guy a NAPA thought the cap looked ok.
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post #11 of 12 (permalink) Old Apr 22nd, 12, 7:07 PM Thread Starter
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blinker tach

I for got to ask, three weeks ago I had to replace the module. The car stumbled and then quit with no spark. What causes the module to go bad and is it possible that at that instance something also attached my tach?
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post #12 of 12 (permalink) Old Apr 22nd, 12, 8:22 PM
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Re: questions not answered

Nailer,
The HEI module generates a signal that makes the tach work. That is what you are connecting to when you hook the tach up to the "Tach" connection on the distributor. It is certainly possible that the module could be bad. I have heard of problems with some of the cheaper store brands. I wouldn't us anything but an AC Delco one myself but I have heard that the NAPA ones are ok.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Enginerepairshop.com

1971 Heavy Chevy - original owner
1984 Buick Riviera - original owner (Wife's car)
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