Tach filter?
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 3,193
Likes: 0
From: Pittsburgh PA
Tach filter?
I was trying to figure out why my tach reads much higher than the engine is running today. I remember reading a thread on here where people mentioned a "tach filter"... I don't see any filter on the tach wire in my car. However, I searched Zip for one and couldn't find anything, and when I googled it I came up with very vague descriptions and no mention of anything Vette-related.
Do HEI setups use tach filters? If so, where do they connect, and where do I buy one?
Thanks!
Jerry
Do HEI setups use tach filters? If so, where do they connect, and where do I buy one?
Thanks!
Jerry
Instructor
Joined: Jul 2003
Posts: 213
Likes: 1
From: zanesville ohio
On my 77 HEI there was a filter of some kind plugged in to it but i think it was to reduce interferance to the radio it looked like a condensor that was used on cars with pionts dist. and i say was because i never put it back on.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by john1977
On my 77 HEI there was a filter of some kind plugged in to it but i think it was to reduce interferance to the radio it looked like a condensor that was used on cars with pionts dist. and i say was because i never put it back on.
i disconnected and tossed that "filter" i assumed it was a capacitor for radio interference and it made no difference on my tachs operation
Burning Brakes
Joined: Nov 2004
Posts: 1,028
Likes: 0
From: San Antonio Texas
on my 79 its on the wire that goes to the "tach" connection on the distributor. its on a little bracket attached to the back of the intake manifold.
primarily for radio interference but i've been told on some vehicles the don't doesn't work right without it.
on the other hand, if you install an MSD ignition sometimes you actually have to remove it to make the take work right (EMI interference with the ignition box).
if it's been working right, i'd suspect the tach itself.
primarily for radio interference but i've been told on some vehicles the don't doesn't work right without it.
on the other hand, if you install an MSD ignition sometimes you actually have to remove it to make the take work right (EMI interference with the ignition box).
if it's been working right, i'd suspect the tach itself.
Drifting
Joined: Oct 2003
Posts: 1,330
Likes: 1
From: Kerrville Texas
Single tan wire coming off the distributor. My Tach totally freaks w/o the thing. Ecklers has them $59? or you can get one from
www.rodneydickman.com has the correct looking one and one for $29.
Kona
www.rodneydickman.com has the correct looking one and one for $29.
Kona
Burning Brakes
Joined: Aug 2004
Posts: 856
Likes: 2
From: Tyler Texas
My 80 L-82 acted the same without a filter: Freaky. In fact my tach filter went bad and I thought it was the tach itself. Turned out it was only the filter. Replaced the filter and tach problem was solved.
There have been lots of threads on this subject. For example, see "tach gone all screwy" thread dated March 1, 2005. I think that thread even has a link to a photo of the tach filter.
There have been lots of threads on this subject. For example, see "tach gone all screwy" thread dated March 1, 2005. I think that thread even has a link to a photo of the tach filter.
Last edited by Patrick73; Apr 16, 2005 at 09:08 PM.
Racer
Joined: Feb 2005
Posts: 258
Likes: 2
From: Boise ID
Mid America has 'em for $50. P/N 618-561.
(50 bucks for a FILTER??
)
I just hooked tach up direct after the wire on my filter broke. I haven't noticed any difference in the tach reading. (I have an 81, no computer).
Dan
(50 bucks for a FILTER??
)I just hooked tach up direct after the wire on my filter broke. I haven't noticed any difference in the tach reading. (I have an 81, no computer).
Dan
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Pro
Joined: Mar 2005
Posts: 559
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From: James Island South Carolina
My '80 tach would go crazy sometimes after working under the hood. I identified the problem as a broken wire right at the filter. I repaired the wire and had no problem afterwards. For awhile. I have to admit, I would just tuck the wire in and drive it until I accidentally bumped it again.
Team Owner
Joined: Apr 2001
Posts: 54,204
Likes: 180
From: S.W. Ohio. . . . . . NRA Life Member
i disconnected and tossed that "filter" i assumed it was a capacitor for radio interference and it made no difference on my tachs operation
it's easy to make the filter yourself:
Melting Slicks
Joined: Oct 1999
Posts: 2,581
Likes: 14
From: Tolar Texas
My home made tach filter cost less than $7.
Tach filter. Wire broke off. Need replacement advice.
http://forums.corvetteforum.com/show...um_id=3&arch=1
Here are some pics of the home built tach filter. I know the pics are crummy but at the time I was using a VERY primitive digital camera.
Tach filter. Wire broke off. Need replacement advice.
http://forums.corvetteforum.com/show...um_id=3&arch=1
Here are some pics of the home built tach filter. I know the pics are crummy but at the time I was using a VERY primitive digital camera.
