[C2] Bad start up
Thread Starter
Pro
Joined: Mar 1999
Posts: 538
Likes: 21
From: Windermere FL
Bad start up
My 65 Corvette with a NOM has a ZZ454 with a Holley Avenger 770 carb w/electric choke. I'm also running a Mallory Unilite distributor. Every day when I go to start my car, I pump the gas pedal 4-5 times, hear the choke set and then start the car.
It will start but initially it seems to run on 2-3 cylinders and takes about 35-45 seconds to eventually run on all 8 cylinders.
The car runs great all day long after that.
I've rebuilt the Holley carb and set the primary and secondary jets with a vacuum gage to 3/4 turn out on each screw, that's where it seems to run best.
Any thoughts or suggestions as to why this engine runs that poorly at start-up? Really appreciate and help. Thanks.
It will start but initially it seems to run on 2-3 cylinders and takes about 35-45 seconds to eventually run on all 8 cylinders.
The car runs great all day long after that.
I've rebuilt the Holley carb and set the primary and secondary jets with a vacuum gage to 3/4 turn out on each screw, that's where it seems to run best.
Any thoughts or suggestions as to why this engine runs that poorly at start-up? Really appreciate and help. Thanks.
Instructor
Joined: Nov 2003
Posts: 176
Likes: 129
From: OH
Before you adjusted your carb, was it running rich? Would it force you out of the garage with watering eyes? 4-5 pumps of the pedal is alot to get the car to start. Mine is one and done. My first guess is the plugs are fouled.
Race Director
Joined: Feb 2007
Posts: 15,454
Likes: 8,913
From: northern california
C2 of Year Finalist (track prepared) 2019
My thought also. What would happen if you pump the accelerator only one time?
Le Mans Master
Joined: Feb 2012
Posts: 5,371
Likes: 2,878
From: Western Massachusetts
2024 C2 of the Year Finalist - Unmodified
2023 C2 of the Year Finalist - Unmodified
2019 C2 of Year Finalist (stock)
2015 C2 of the Year Finalist
Dan
Race Director
Joined: Jul 2018
Posts: 10,587
Likes: 8,409
From: San Antonio, TX/Mahopac, NY
2026 Restomod of the Year Winner
2024 Corvette of the Year Finalist - Modified
2024 Corvette of the Year Finalist - Unmodified
2023 C7 of the Year Winner - Modified
One pump on my L72 and she is good to go. Once I when it was colder, I gave it three and it loaded up and ran like crap for the first 4 or 5 minutes. Sounds like that is your problem.
Race Director
Joined: Jan 2003
Posts: 17,681
Likes: 3,678
From: Central Arkansas
You might also check you choke pull off adjustment to make sure it’s opening the choke plate sufficiently upon firing to avoid an over-rich condition initially which will make for rough running. I’m experiment in with this on a couple of my cars. Stored in a garage with temps in the 60s, the usual choke factory adjustments seem to be too rich so I’m opening up the choke pull uff on my Corvette. On a car with an AFB and self contained thermostatic choke coil (no pull off) I’m setting it to the lean side to reduce a too rich condition and rough running.
Le Mans Master
Joined: Feb 2007
Posts: 9,296
Likes: 1,531
From: Oviedo Florida
2024 C5 of the Year Finalist - Modified
2024 C2 of the Year Finalist - Modified
2023 C2 of the Year Finalist - Modified
2021 C2 of the Year Finalist - Modified
2016 C5 of Year Finalist
Clean or replace your plugs. Too much gas
at start up. Your engine should run on all 8
cylinders not 3 or 4.
Good luck
at start up. Your engine should run on all 8
cylinders not 3 or 4.
Good luck
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
Thread Starter
Pro
Joined: Mar 1999
Posts: 538
Likes: 21
From: Windermere FL
Well, the last couple of days, I've been hitting accelerator once to set choke and one small shot, car starts right up and runs on all 8 cylinders. I'll check/change out the plugs if necessary.
I drove it for 100 miles in 2 days and it drove great.
There's that old saying, "you can't teach and old dog new tricks", well this old dog learned a new one for future reference. Pure stupidity on my part.
Thanks guys.
I drove it for 100 miles in 2 days and it drove great.
There's that old saying, "you can't teach and old dog new tricks", well this old dog learned a new one for future reference. Pure stupidity on my part.
Thanks guys.
Race Director
Joined: Feb 2007
Posts: 15,454
Likes: 8,913
From: northern california
C2 of Year Finalist (track prepared) 2019
Get out on the highway and drive at highway speeds for several miles and the plugs will clean themselves. No need to do anything special.
