Hello everyone, I have an interesting ignition timing issue.
First off, I am a mechanic of 20+ years. I have worked on lots of carbureted vehicles through the years, but this one of mine has got me stumped.
I have a 69 Skylark, with a 1970 455 in it. It has an HEI distributor, and a Holley double pumper carb. I built this engine 20 years ago, as a young apprentice in the trade. When its running and driving, it runs really strong with no apparent issues, lots of power and excellent throttle response.
My issue is starting and idling. The carb setup seems to be dialed in the best it can be, as far as idle mixture etc. But it does have the choke locked open. (Which I realize, makes it harder to start cold, but should be fine once its warned up)
The main issue I am concerned with is how my ignition timing seems to be operating. I have the vacuum advance disconnected and some lighter springs for the mechanical weights. I was told by an old guru, years ago, to just set the total timing at 2500 rpms. Which I set at 30 degrees at 2500 rpms. The car runs really strong at this setting, but at idle in gear, seems to be loading up, and stalls once in a while. And its really tricky to start, even warmed up. Sometimes backfires up the carb too. So I went and checked the ignition timing at idle, and with a digital timing light, it appears the at idle timing goes up to 46 degrees! That explains why the backfiring up the carb. My question is, why is this happening?
With the engine running at about 900 rpms idle, the timming seams way out. When I bring it up to 2500 rpms, the total timing is right at 30 degrees. So it seems like the mechanical weights are pulling it the wrong way? Everything in the distributer seems to work fine, the weights are nice and free, and the vacuum is disconnected. What am I doing wrong?
I have checked a lot of vehicle timing before, and usually when you check total timing at 2500, it always goes down to like 10 degrees or so at idle.
This one has stumped me for a while. Like I said, driving down the road, it runs excellent, with lots of power! Like a 455 should! Its just this idle/starting issue. I have had lots of cars with the choke locked open, so I know thats not the issue. Something is incorrect with the timing, and I haven’t figured it out. If anyone has any ideas, that would be great!
First off, I am a mechanic of 20+ years. I have worked on lots of carbureted vehicles through the years, but this one of mine has got me stumped.
I have a 69 Skylark, with a 1970 455 in it. It has an HEI distributor, and a Holley double pumper carb. I built this engine 20 years ago, as a young apprentice in the trade. When its running and driving, it runs really strong with no apparent issues, lots of power and excellent throttle response.
My issue is starting and idling. The carb setup seems to be dialed in the best it can be, as far as idle mixture etc. But it does have the choke locked open. (Which I realize, makes it harder to start cold, but should be fine once its warned up)
The main issue I am concerned with is how my ignition timing seems to be operating. I have the vacuum advance disconnected and some lighter springs for the mechanical weights. I was told by an old guru, years ago, to just set the total timing at 2500 rpms. Which I set at 30 degrees at 2500 rpms. The car runs really strong at this setting, but at idle in gear, seems to be loading up, and stalls once in a while. And its really tricky to start, even warmed up. Sometimes backfires up the carb too. So I went and checked the ignition timing at idle, and with a digital timing light, it appears the at idle timing goes up to 46 degrees! That explains why the backfiring up the carb. My question is, why is this happening?
With the engine running at about 900 rpms idle, the timming seams way out. When I bring it up to 2500 rpms, the total timing is right at 30 degrees. So it seems like the mechanical weights are pulling it the wrong way? Everything in the distributer seems to work fine, the weights are nice and free, and the vacuum is disconnected. What am I doing wrong?
I have checked a lot of vehicle timing before, and usually when you check total timing at 2500, it always goes down to like 10 degrees or so at idle.
This one has stumped me for a while. Like I said, driving down the road, it runs excellent, with lots of power! Like a 455 should! Its just this idle/starting issue. I have had lots of cars with the choke locked open, so I know thats not the issue. Something is incorrect with the timing, and I haven’t figured it out. If anyone has any ideas, that would be great!