tach drive or HEI?
Thread Starter
Instructor
Joined: Aug 2007
Posts: 122
Likes: 0
From: Enterprise Ut
tach drive or HEI?
The 74 I bought has an HEI distributor with no tach drive so no tach. I was going to swap a thach head out of a 75-77 but it needs a board. While surfing e-bay I seen tachdrive HEI distributors with cap rotor and the coil for around $140. Has anyone bought one? Are they ok or crap? That seems way cheap. Are there more problems with tachdrive, or HEI tachs? Which way should I go?? Any thoughts are appreciated
Advanced
Joined: Mar 2005
Posts: 80
Likes: 0
From: Sunnyvale California
Ditto. I have a similar one, runs perfectly. The only difference between this and the normal HEI is main shaft has an accomodation for a cross-drive gear to run the mechanical tach drive. Otherwise, it's all off-the-shelf HEI stuff, which is pretty bombproof. Furthermore, if you ever need any replacement stuff, you can get it at your local auto parts store.
Drifting
Joined: Jul 2002
Posts: 1,944
Likes: 20
From: The only Corvettes in Highett Victoria
Mickey,
I agree with the two P's. I've had one for five years now and it works every time. Only trouble is, I had to modify it to run backwards, as engines go the other way on this side of the equator.
Regards from Down Under
aussiejohn
I agree with the two P's. I've had one for five years now and it works every time. Only trouble is, I had to modify it to run backwards, as engines go the other way on this side of the equator.
Regards from Down Under
aussiejohn
Le Mans Master
Joined: Oct 2005
Posts: 9,429
Likes: 44
From: Macon, GA
Forum sponsor Speed City Motors sells them. Mine works good.
http://forums.corvetteforum.com/show....php?t=1629348
http://forums.corvetteforum.com/show....php?t=1629348
Team Owner
Joined: Jul 2004
Posts: 40,265
Likes: 786
From: Redondo Beach, California
I bought a tach drive HEI several years ago from one of the major Corvette vendors (forget who). I think it was over $400. It was probably expensive since it was the first time they were available.
I removed the vacuum advance can, springs and weights, and even the eletronics from the HEI that came with my ZZ4 and installed them in the tach drive HEI. Also, I removed the gear drive from the aftermarket HEI and installed the one that came on the ZZ4 HEI.
Runs fine. Also, the angle that the tach cable mates up to the tach drive HEI is just right. With the tach cable in, the Number 1 and Number 8 distributor contact lugs are perfectly aligned orthogonal to the center line of the car.
I removed the vacuum advance can, springs and weights, and even the eletronics from the HEI that came with my ZZ4 and installed them in the tach drive HEI. Also, I removed the gear drive from the aftermarket HEI and installed the one that came on the ZZ4 HEI.
Runs fine. Also, the angle that the tach cable mates up to the tach drive HEI is just right. With the tach cable in, the Number 1 and Number 8 distributor contact lugs are perfectly aligned orthogonal to the center line of the car.
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Drifting
Joined: Jul 2003
Posts: 1,253
Likes: 1
From: East China MI
Main Entry: or·thog·o·nal
Function: adjective
Etymology: Middle French, from Latin orthogonius, from Greek orthogOnios, from orth- + gOnia angle -- more at -GON
1 a : intersecting or lying at right angles b : having perpendicular slopes or tangents at the point of intersection <orthogonal curves>
2 : having a sum of products or an integral that is zero or sometimes one under specified conditions: as a of real-valued functions : having the integral of the product of each pair of functions over a specific interval equal to zero b of vectors : having the scalar product equal to zero c of a square matrix : having the sum of products of corresponding elements in any two rows or any two columns equal to one if the rows or columns are the same and equal to zero otherwise : having a transpose with which the product equals the identity matrix
3 of a linear transformation : having a matrix that is orthogonal : preserving length and distance
4 : composed of mutually orthogonal elements <an orthogonal basis of a vector space>
5 : statistically independent
Function: adjective
Etymology: Middle French, from Latin orthogonius, from Greek orthogOnios, from orth- + gOnia angle -- more at -GON
1 a : intersecting or lying at right angles b : having perpendicular slopes or tangents at the point of intersection <orthogonal curves>
2 : having a sum of products or an integral that is zero or sometimes one under specified conditions: as a of real-valued functions : having the integral of the product of each pair of functions over a specific interval equal to zero b of vectors : having the scalar product equal to zero c of a square matrix : having the sum of products of corresponding elements in any two rows or any two columns equal to one if the rows or columns are the same and equal to zero otherwise : having a transpose with which the product equals the identity matrix
3 of a linear transformation : having a matrix that is orthogonal : preserving length and distance
4 : composed of mutually orthogonal elements <an orthogonal basis of a vector space>
5 : statistically independent
Burning Brakes
Joined: May 2006
Posts: 865
Likes: 53
tach drive or HEI
I bought one. The first one blew up . The company (Star Performance I think) sent a second one. It took a long time , and it was different. Since then , no problem , and my tach works perfect .
Drifting
Joined: May 2005
Posts: 1,909
Likes: 6
From: Lake Arrowhead - Georgia > 72 Base Coupe & 74 BB Roadster
I just last week replaced my wore out points style unit with the item you speak of. It cured ALL of my tuning problems on my recently rebuilt 1974 454. I will rebuild the original and keep it just so I still have it. I never realized how much bad effect a sloppy distributor had on an engine.
Racer
Joined: Sep 2004
Posts: 495
Likes: 1
From: Spokane Washington
Shielding
Anyone tried to use the original shielding. Will the 75 shilding box cover the HEI unit, I do not believe the 74 and under will work. I know most people leave it off, but I like the look.
cal
cal
Le Mans Master
Joined: Jan 2001
Posts: 6,660
Likes: 1,357
I've had both....
I have an MSD Tach Drive which I used for several years. When I replaced my engine with a Ramjet 350 I had to decide what to do and I just bought an electric tach from a 75-77. I must say that the electric tach is a lot easier to deal with.
Having said that, that price mentioned for speedcitymotors would be hard to beat. The electric tach that I bought cost me about 60 bucks and then I had to buy the tach card for about 70-80 bucks. While I like having the electric tach a lot better than the mechanical tach, it does involve getting behind the dash...which is quite the pain.
Having said that, that price mentioned for speedcitymotors would be hard to beat. The electric tach that I bought cost me about 60 bucks and then I had to buy the tach card for about 70-80 bucks. While I like having the electric tach a lot better than the mechanical tach, it does involve getting behind the dash...which is quite the pain.