69427
The Artist formerly known as Turbo84
Hauled the '69 up to Indiana and Michigan for some autocross and track time a couple weeks ago. The autocross was a get together with some old friends where I used to live in Indiana, and also a good opportunity to put a decent load on the engine to get the rings seated. The car and engine ran well, with no problems, so I was relieved to finish the event with all the parts in the same place (and condition) as when I got there.
Later in the week a few of us went up to Gingerman Raceway in Michigan for a test and tune session. I got there earlier than the rest of the gang, and installed my WBO2 sensor in the tailpipe to check what the carb was doing out on the track.
The engines that I've had this carb (Holley 3310 780CFM) on have always run well, with good throttle response, so I didn't expect to see that the A/F ratio was very far off.
The car ran great out on the track, with the A/F ratio looking just a touch rich (11.9) at WOT. No big deal. I could tweak it down the road when I got caught up with other things.
About 15 minutes into the first session things changed. I came into one of the corners as usual, braked hard, and then hit the throttle coming out. Instead of some smooth acceleration all I got was a burbling noise out of the exhaust as I applied the throttle. Scared the crap out of me, and I lifted out of the throttle. The engine smoothed right out when I did that, so I figured I didn't grenade anything, so I gave it a little more throttle to try to figure out what happened. As soon as I gave it more than about 10-15% throttle it would fall on its face again, and the WBO2 readout would climb higher the more throttle I gave it. At 20-25% throttle the O2 readout would climb to 20-22 A/F ratio. I nursed it a couple miles around the rest of the track and into the pits. The engine would idle fine there in the pits, but go lean when I applied any throttle.
So, I'm back home now and am going to try to figure out what happened. My first thought is that a piece of crap somehow got in and plugged one of the main jets. This would lean it out under load. A plugged filter would starve things, but it shouldn't have been able to plug so quickly. I checked the bowl fuel level and it was where it was supposed to be, so fuel is getting to the carb, I just haven't checked the level as the engine is being revved to see if the pump is keeping up.
So, that's where I'm at. The car is still in the trailer and I'm hoping it will run well enough to get up the driveway and also up on the car lift into the garage.
Am I missing anything here? Input is welcome here.
Later in the week a few of us went up to Gingerman Raceway in Michigan for a test and tune session. I got there earlier than the rest of the gang, and installed my WBO2 sensor in the tailpipe to check what the carb was doing out on the track.
The engines that I've had this carb (Holley 3310 780CFM) on have always run well, with good throttle response, so I didn't expect to see that the A/F ratio was very far off.
The car ran great out on the track, with the A/F ratio looking just a touch rich (11.9) at WOT. No big deal. I could tweak it down the road when I got caught up with other things.
About 15 minutes into the first session things changed. I came into one of the corners as usual, braked hard, and then hit the throttle coming out. Instead of some smooth acceleration all I got was a burbling noise out of the exhaust as I applied the throttle. Scared the crap out of me, and I lifted out of the throttle. The engine smoothed right out when I did that, so I figured I didn't grenade anything, so I gave it a little more throttle to try to figure out what happened. As soon as I gave it more than about 10-15% throttle it would fall on its face again, and the WBO2 readout would climb higher the more throttle I gave it. At 20-25% throttle the O2 readout would climb to 20-22 A/F ratio. I nursed it a couple miles around the rest of the track and into the pits. The engine would idle fine there in the pits, but go lean when I applied any throttle.
So, I'm back home now and am going to try to figure out what happened. My first thought is that a piece of crap somehow got in and plugged one of the main jets. This would lean it out under load. A plugged filter would starve things, but it shouldn't have been able to plug so quickly. I checked the bowl fuel level and it was where it was supposed to be, so fuel is getting to the carb, I just haven't checked the level as the engine is being revved to see if the pump is keeping up.
So, that's where I'm at. The car is still in the trailer and I'm hoping it will run well enough to get up the driveway and also up on the car lift into the garage.
Am I missing anything here? Input is welcome here.
