73 vs 75?
Thread Starter
Instructor
Joined: Sep 2005
Posts: 195
Likes: 0
From: Lancaster CA
Is this a hard question? Maybe I should ask on some other board. Sometimes I feel like this board is like the club I was in=too clicky
Do you have to post a ton to get questions answered??
Do you have to post a ton to get questions answered??
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You don't have to "rewire" the entire engine compartment to change from points to an HEI ignition system. But, and HEI distributor won't fit under the chrome ignition shielding installed on the '73. You can get the same result from just purchasing a Pertronix electronic ignition module that fits in your present distributor.
But, there is no real disadvantage to keeping the original points system that you have. Change the condenser every couple of years; change the points after about 20,000 miles and clean/file them every year. They will function just as well as any electronic ignition system if you have just a stock GM engine. If you have an engine that will crank over 7000 rpm, you need to go electronic. Otherwise, my advice would be to keep what you have....just make it work like it was intended.
But, there is no real disadvantage to keeping the original points system that you have. Change the condenser every couple of years; change the points after about 20,000 miles and clean/file them every year. They will function just as well as any electronic ignition system if you have just a stock GM engine. If you have an engine that will crank over 7000 rpm, you need to go electronic. Otherwise, my advice would be to keep what you have....just make it work like it was intended.
Burning Brakes
Joined: Oct 2001
Posts: 1,241
Likes: 4
From: Okinawa Okinawa
Not sure what the differences are in the 73 to 75 wiring harness. I have a 74 schematic and know it quiet well. That may be the problem. Unless someone has a 73 and 75 schematic to look at, it may be hard to answer the question.
I'm w/ 7T1vette, I would use your current distributor or rewire just for the HEI dizzy. I put in a ZZ4 last year and took out the HEI and inserted my MSD dizzy. If you don't want the points, go with Pertronix electronic ignition module.
I'm w/ 7T1vette, I would use your current distributor or rewire just for the HEI dizzy. I put in a ZZ4 last year and took out the HEI and inserted my MSD dizzy. If you don't want the points, go with Pertronix electronic ignition module.
Race Director
Joined: Jul 2004
Posts: 12,710
Likes: 329
From: Scottsdale Arizona
The answer to your question is almost certainly yes. I'm not sure I'd bother though. If you want to replace your engine harness (usually a very good idea) then I would go with a 73 harness and add on the HEI wire to the plug. The wire is available separately from Lectric Limited and is very easy to swap out. As others have suggested, you can also simply add the connector to your existing harness. You'll have a the coil bypass wire from the starter left over though.
I don't recall how the tach is wired and I'd be a little concerned that the fuse box positions might not match up with the 73 . Shouldn't be hard to verify but I'd do that before making a leap of faith.
I don't recall how the tach is wired and I'd be a little concerned that the fuse box positions might not match up with the 73 . Shouldn't be hard to verify but I'd do that before making a leap of faith.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Le Mans Master
Joined: May 2007
Posts: 5,036
Likes: 1,121
From: North tonawanda NY
I upgrade my 74 with a mechanical tach drive HEI unit ..... all That's needed is one wire ran from the 12v ingition switched power at the fuse box? There may be other wiring differences between the 75 and 73 harness.... I would stick with a 73 harness.
I see more failures reported here with the electronic 75+ tach systems than the mechanical ones.....
I see more failures reported here with the electronic 75+ tach systems than the mechanical ones.....
Le Mans Master
Joined: May 2007
Posts: 5,036
Likes: 1,121
From: North tonawanda NY
No disrespect but the impression your giving me is either YOUR the non friendly one or your suffering from an OCD disorder... are you a neat freak? I,m just trying you understand the reasons for doing what your doing... that's not unreasonable to expect when you ask about something that's not normally done? In fact it helps one answer the question more effectively if they understand your motives. Instead of giving them you instantly get offensive?
Melting Slicks
Joined: Jul 2010
Posts: 2,503
Likes: 33
From: McGrady NC
St. Jude Donor '15-'16
Personally, I would keep the tach-drive distributor so the tach in the dash will still work as intended. Add the Pertronix module to the factory dizzy. That will save a bunch of modifications and still work good. If it worked for an LT-1 or L-88 it will work fine for your ZZ4. Put the shielding back on tell everyone you are running a 305 to save gas.
BTW, just a bunch of good people here who want to help but probably have other stuff to do occasionally. This isn't Facebook where we live our lives through an endless stream of mindless postings. Remember, good things come to those who wait. I was new here once myself so I speak from experience. We all want to be friends and help each other every chance we get. That definitely include anyone just coming on board.
BTW, just a bunch of good people here who want to help but probably have other stuff to do occasionally. This isn't Facebook where we live our lives through an endless stream of mindless postings. Remember, good things come to those who wait. I was new here once myself so I speak from experience. We all want to be friends and help each other every chance we get. That definitely include anyone just coming on board.
Racer
Joined: Nov 2006
Posts: 435
Likes: 7
From: Wake Forest NC
I take it you want to replace the engine harness. The HEI and tach both get power from the interior harness via fusebox and firewall disconnect, so you'd have to match the connections. The HEI doesn't use a ballast like points. Early 75 also has the seatbelt/starter interlock circuit, as if the starter path doesn't have enough points of weakness. You're talking hundreds of dollars for harnesses...