69 427 coil replacement question
Thread Starter
Pro
Joined: May 2013
Posts: 570
Likes: 22
69 427 coil replacement question
I am trying to diagnose a rough running condition in my 69 C3 tri power. Carb has recently been rebuilt by Lars I’ve set timing according to Lars paper, replaced wires and plugs. I am experiencing rough acceleration and poor power delivery. I have read it could be the coil and want to rule out all ignition causes before moving on to something else
what is the correct coil for my vehicle? It is a 427 with transistorized ignition.
what is the correct coil for my vehicle? It is a 427 with transistorized ignition.
Burning Brakes
Joined: Jul 2016
Posts: 767
Likes: 74
From: Blaine MN
You need a TI Coil, go to this site http://www.tispecialty.com there's plenty of info there for you to figure out if you have the correct coil. I bought the lower cost (non-correct markings) coil one of the online vendors. (can't remember which vendor, sorry)
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Has any of the ignition system been modified? If not and it has the stock TI system, it needs the stock TI coil
The TI coil has much different specs that the points ignition. Primary resistance = .41 to .51 ohms; secondary resistance = 3000 to 20,000 ohm; But the TI wiring harness has two fixed resistor wires in it. I don't have the P/N for a '69 TI coil, but I'm sure someone will post it for you.
The TI coil has much different specs that the points ignition. Primary resistance = .41 to .51 ohms; secondary resistance = 3000 to 20,000 ohm; But the TI wiring harness has two fixed resistor wires in it. I don't have the P/N for a '69 TI coil, but I'm sure someone will post it for you.
Melting Slicks
Joined: Jan 2000
Posts: 3,326
Likes: 523
From: home
Did you check the pickup coil for intermittent opens? Check the two wires coming out of the pickup coil where they bend around the breaker plate before going through the grommet. They've been known to break there. Does the amp case have a very good ground connection? If led to it being a coil issue, I'd Call Dave at T.I.Specialty and see if he has any coils for sale. The last time I spoke with him, he was in the process of reproducing the correct coil. I would steer far away from the Chinese ones that are available. I've heard to many problems people are having with them. I believe the correct GM number is 1115207. Stay away from the 1233766 coil. The T.I. Specialty website has some good information and diagnosis flow charts.
Last edited by 3X2; Jun 2, 2019 at 08:21 AM. Reason: spelling
Melting Slicks
Joined: Jan 2000
Posts: 3,326
Likes: 523
From: home
Possibly. Not to give such a vague answer. You could also check for the fuel cap not venting and check for low fuel pressure. Did you get Lars's papers on tuning and timing? Look for carbon tracking on the coil and for cracks. My original t.i coil had a crack from one of the small terminals over to the metal can.
Thread Starter
Pro
Joined: May 2013
Posts: 570
Likes: 22
Possibly. Not to give such a vague answer. You could also check for the fuel cap not venting and check for low fuel pressure. Did you get Lars's papers on tuning and timing? Look for carbon tracking on the coil and for cracks. My original t.i coil had a crack from one of the small terminals over to the metal can.
Melting Slicks
Joined: Jan 2000
Posts: 3,326
Likes: 523
From: home
Replacing is an option. Suggesting- not saying to do this- drill a 3/16" hole through the cap to vent the tank. <----- do this at your own risk of fuel spillage when driving. A new vented cap is probably the better choice. You will need a fuel pressure gauge to check pressure. How are the fuel filters in all the carbs? I'll assume they are clean since you just had the carbs rebuilt.
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: May 2013
Posts: 570
Likes: 22
Replacing is an option. Suggesting- not saying to do this- drill a 3/16" hole through the cap to vent the tank. <----- do this at your own risk of fuel spillage when driving. A new vented cap is probably the better choice. You will need a fuel pressure gauge to check pressure. How are the fuel filters in all the carbs? I'll assume they are clean since you just had the carbs rebuilt.
Yes the filters were replaced when Lars rebuilt the carb. The issue seems to occur after the engine is warmed up on hard acceleration.
Drifting
Joined: Nov 2002
Posts: 1,787
Likes: 261
From: Blue Bell PA
2018 C3 of Year Finalist
I hate to chime in here but is there a problem with the
accelerator pump adjustment. Mine sure does it if it
does not have a small amount of play. Thought it just might help.
accelerator pump adjustment. Mine sure does it if it
does not have a small amount of play. Thought it just might help.