Mechanical 3x2?
Le Mans Master
Joined: Apr 2001
Posts: 9,556
Likes: 288
From: Granbury Texas
Now the mechanical secondaries worked.....BUT, neither kit would open the end carbs ALL the way open when the center carb was wide open. The second kit worked better, but had the same problem. Also, there is a definite "step" to get the end carbs open. some people who drove my car simply refused to believe that there were secondaries to open cause they thought they were flat on the floor. When the end carbs do open, they provide fairly sudden amounts of torque, so that say, in a corner, you can get throttle oversteer. Still, I thought they were much better than the vacuum....just not perfect.
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
I'm surprised there are any vacuum set ups left for the older tri power Pontiacs, Oldsmobiles and Chevys. Many of them went in the garbage. I don't think Ford used the vacuum linkage on their 3 X 2's. Think it was all mechanical.
Le Mans Master
Joined: Jan 2007
Posts: 6,004
Likes: 1,509
From: Prescott Arizona
Pontiac did use a vacuum operated Tripower for manual trans '64 GTO's but it wasn't a good design because instead of a separate vacuum cannister on each of the secondary carbs, there was a single cannister and that operated the front and rear carbs via linkage. My '64 came with that setup but most people converted their '64's to the same progressive linkage the factory went to for '65 and '66 and that's what I did as well.
A progressive/mechanical tripower setup isn't as forgiving as a vacuum style tripower. Have it incorrectly adjusted or hit it when your rpm is too low and it can be bog city.
Mike T.
A progressive/mechanical tripower setup isn't as forgiving as a vacuum style tripower. Have it incorrectly adjusted or hit it when your rpm is too low and it can be bog city.
Mike T.
Last edited by Vet65te; Aug 10, 2010 at 08:27 AM.
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
Le Mans Master
Joined: Jan 2007
Posts: 6,004
Likes: 1,509
From: Prescott Arizona
Got to say there is a learning curve alright. I only have about 750 miles on my '64 3x2 GTO with 3:23 gears since I put it together in '02 and the car is quite responsive. But, I have the secondaries set so that I'm into the primaries for over half the throttle movement, with the secondaries not coming in till around 65% thottle which is higher than the factory had it in 65/66, but if I'm in a higher gear coming on the freeway and just around 2K rpm, stomping the go-pedal doesn't do a whole bunch of anything and downshifting becomes a necessity.
For most people used to the smoother introduction of secondaries with 4 barrels or tripowers, a mechanical setup takes some getting used to.
Mike T.
For most people used to the smoother introduction of secondaries with 4 barrels or tripowers, a mechanical setup takes some getting used to.
Mike T.
Last edited by Vet65te; Aug 10, 2010 at 08:29 AM.
Melting Slicks
Joined: Oct 2003
Posts: 2,189
Likes: 830
From: Chapel Hill NC
2025 c3 ('68-'73) of the Year Finalist - Unmodified
2025 C4 of the Year Finalist - Unmodified
2025 C8 Stingray of the Year Finalist - Unmodified
Back in the day my DD was a 68 L89 with mechanical secondaries. PO installed them, I readjusted them. Never had any bog issues and the car ran like a wild beast on steroids.
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
Your waisting your time trying to make a 435 into mechanical linkage.
....there are no pumps in the outboard carbs....Besides a good setup {not fuked with} works quite well.....same as a FI car that's left alone.......You cant re-engineer what GM proved works......
....there are no pumps in the outboard carbs....Besides a good setup {not fuked with} works quite well.....same as a FI car that's left alone.......You cant re-engineer what GM proved works......
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
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
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Melting Slicks
Joined: Mar 2001
Posts: 2,372
Likes: 51
From: New Milford CT
I did it to my 1967 427/400hp vette when it was 2 years old in 1969. Progressive mechanical linkage and I had no problem to get full throttle on all 3 carbs. Mine worked just fine, no bogging, even at lower rpm, but that was with the mild cam 400 hp. Very nice to feel the hard surge when the end carbs slam open, feels like down shifting.
