After fire on an L46
Thread Starter
---------
Joined: Jul 2010
Posts: 1,839
Likes: 20
From: NC
Afterfire on an L46
Slowly working the kinks out of my 69. Today I went after the afterfire on the passenger side which occurs after wot. I understand this is a condition usually caused by a lean mixture. I redid the mixture settings starting from scratch. The best vacuum I can get is 15-20 on the gauge.
Adjusting the mixture did not fix the problem. Any other suggestions?
Little info on car
Holley 4165/75 series carb
Msd ignition
Side pipes. (not that it matters? ). No headers
53k miles on the clock
Adjusting the mixture did not fix the problem. Any other suggestions?
Little info on car
Holley 4165/75 series carb
Msd ignition
Side pipes. (not that it matters? ). No headers
53k miles on the clock
Last edited by binster; Jun 25, 2011 at 03:43 PM.
Race Director
Joined: May 2006
Posts: 18,710
Likes: 2,574
what jets are you using primary and secondary? are the floats correctly adjusted? what is you total mechanical timing and if you have a vacuum advance unit how much is it adding? 4165 has mechanical secondaries, 4175 has vacuum which do you have? what is the list# of the carburetor, you can find it on the air horn?
Thread Starter
---------
Joined: Jul 2010
Posts: 1,839
Likes: 20
From: NC
what jets are you using primary and secondary? are the floats correctly adjusted? what is you total mechanical timing and if you have a vacuum advance unit how much is it adding? 4165 has mechanical secondaries, 4175 has vacuum which do you have? what is the list# of the carburetor, you can find it on the air horn?
Timing was 12 btdc with the advance off.. advance appears to add about 2 decrees. The manual I have says 4 for the setting at 800 rpm. I can't get it back that far due to the vac advance hitting the bracket.. But I am wondering if 4 is the right setting? i cranked it back to around 5-6 and had a backfire through the carb, but the afterfilre seems to cleared?
Thread Starter
---------
Joined: Jul 2010
Posts: 1,839
Likes: 20
From: NC
Update.. I ended up setting the timing around 10.. just to see if that helped.. It looks like the afterfire is gone, and I just have some exhaust popping which I think is normal (plus I kinda like the sound).
I did find a loose wire on cyl 4, but correcting that did not have any effect. I guess it is something that would have haunted me later.
Thanks for the input all..
I did find a loose wire on cyl 4, but correcting that did not have any effect. I guess it is something that would have haunted me later.
Thanks for the input all..
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
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
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Le Mans Master
Joined: Jan 2000
Posts: 8,721
Likes: 108
From: Canada
Been getting a lot of after fire lately as well, checked the header bolts and 2 beside each other were very loose. Took them out to check and dropped one, of course can't find it now off to pick up a replacement. If tightening these loose header bolts doesn't fix the issue will get into the carb next.
