Voeltagear
Well-Known Member
Happy Saturday everyone!
Since we've had the 76 Aspen 4spd "little red express" home I've been working on getting it to idle and operate smoothly under light throttle. Power circuit is flawless and it runs best under a load. It wouldn't stay running without throttle input and it sounded like a radical camshaft profile under light throttle.
The first thing I tackled on the good old 318 was the idle jet cleaning. Not too difficult and it made a huge improvement. At first it idled smoothly and stayed running at stops no problem. A lot less choppy off idle but still noticeable. Fun to drive, right?
Then it began to have a wandering idle. Sometimes 1100 rpm and smooth other times less than 500 rpm shaking badly and worst case died out. Every time I was about to dive back into the carb it would run great the next time I drove it.
Finally after about 3 days it was idling rough at about 500rpm when good and warmed up almost every time I drove it. Light throttle still choppy. So I decided to take another look.
When I removed the dust cover screw from the bowl vent the step up piston pushed the cover up. Not what I expected. So curious as I am, I decided to disassemble the accelerator pump rod and investigate.
I pulled out the step up assembly and found wear marks on the step up rods from contact with the bowl cover. The step up spring was a little bent but seemed to push the piston up without hanging up. Also the wire on top was not contacting the rods so I repositioned it to the correct location.
Nothing else looked out of place so I reassembled the step up assembly. Following the installation instructions I locked it down to the accelerator pump shaft. I set the accelerator pump to 1/2" below the dust cover mounting surface with the idle screw turned in 2 turns after contact. I also blew out the idle jets again. I found nothing restricting them and reinstalled them.
This time it ran beautifully. Idle was smooth and it was responsive. I set the idle air with my trusty vacuum gauge and off I went. A pleasure to drive! At last! Well at least that's what I thought.
The wife and I drove it to dinner and all was well. Even driving home it was pretty unnoticeable. But I noticed. The light throttle choppieness is back.
Today I drove it about 20 highway miles and as long as I'm cruising under any load its great. Rolling downhill with light throttle it's noticeable.
Other than that it idles at 550 rpm, doesn't die at stops, has great under load power and its enjoyable to drive.
So does anyone know how to get the light throttle AF corrected on this Carter BBD? Are there tuning parts available like the Edelbrock AVS carbs? Step up springs? Rods? Or is it matter of trial and error with the step up assembly? I did see some threads about drilling out the idle jets somewhere. Not sure if that would help light throttle.
Any ideas are appreciated, thanks for reading.
Since we've had the 76 Aspen 4spd "little red express" home I've been working on getting it to idle and operate smoothly under light throttle. Power circuit is flawless and it runs best under a load. It wouldn't stay running without throttle input and it sounded like a radical camshaft profile under light throttle.
The first thing I tackled on the good old 318 was the idle jet cleaning. Not too difficult and it made a huge improvement. At first it idled smoothly and stayed running at stops no problem. A lot less choppy off idle but still noticeable. Fun to drive, right?
Then it began to have a wandering idle. Sometimes 1100 rpm and smooth other times less than 500 rpm shaking badly and worst case died out. Every time I was about to dive back into the carb it would run great the next time I drove it.
Finally after about 3 days it was idling rough at about 500rpm when good and warmed up almost every time I drove it. Light throttle still choppy. So I decided to take another look.
When I removed the dust cover screw from the bowl vent the step up piston pushed the cover up. Not what I expected. So curious as I am, I decided to disassemble the accelerator pump rod and investigate.
I pulled out the step up assembly and found wear marks on the step up rods from contact with the bowl cover. The step up spring was a little bent but seemed to push the piston up without hanging up. Also the wire on top was not contacting the rods so I repositioned it to the correct location.
Nothing else looked out of place so I reassembled the step up assembly. Following the installation instructions I locked it down to the accelerator pump shaft. I set the accelerator pump to 1/2" below the dust cover mounting surface with the idle screw turned in 2 turns after contact. I also blew out the idle jets again. I found nothing restricting them and reinstalled them.
This time it ran beautifully. Idle was smooth and it was responsive. I set the idle air with my trusty vacuum gauge and off I went. A pleasure to drive! At last! Well at least that's what I thought.
The wife and I drove it to dinner and all was well. Even driving home it was pretty unnoticeable. But I noticed. The light throttle choppieness is back.
Today I drove it about 20 highway miles and as long as I'm cruising under any load its great. Rolling downhill with light throttle it's noticeable.
Other than that it idles at 550 rpm, doesn't die at stops, has great under load power and its enjoyable to drive.
So does anyone know how to get the light throttle AF corrected on this Carter BBD? Are there tuning parts available like the Edelbrock AVS carbs? Step up springs? Rods? Or is it matter of trial and error with the step up assembly? I did see some threads about drilling out the idle jets somewhere. Not sure if that would help light throttle.
Any ideas are appreciated, thanks for reading.
