Twin impco 425 adjustment advice
Posted: Mon May 03, 2021 3:40 am
Hi all,
Got myself a new project. A nice 454 chevy which now has a twin Impco 425 setup.
They're running of a regular intake with a large holley throttle plate and the "Y" adapter to mount 2 425's on one throttle plate.
The car has been started for the first time recently, and i'm trying to tune the Impco 425's using an AFR meter in the exhuast.
What I noticed with the factory settings on both Impco's is that it was running lean at idle, and much and much leaner at higher RPMs (19.x+).
I've adjusted the idle mixture to make it run much richer at idle to start with. However, it's still goes to 17.x+ at higher RPM.
Since it goes from rich to lean depending on the RPM's, I suspect that both Impco's have completely different idle mixture settings causing them to run "out of sync".
What would be the best way to tune them identical? I doubt that counting the number of turns on the idle mixture screw is anything near exact.
I saw someone on the internet stating to close one air valve so the system will run on one 425, allowing it to adjust that 425. But sounds a bit weird to me, although it might work.
I'm pretty sure there are people here with more expensive of knowing to adjust twin 425 .
Thanks!
Got myself a new project. A nice 454 chevy which now has a twin Impco 425 setup.
They're running of a regular intake with a large holley throttle plate and the "Y" adapter to mount 2 425's on one throttle plate.
The car has been started for the first time recently, and i'm trying to tune the Impco 425's using an AFR meter in the exhuast.
What I noticed with the factory settings on both Impco's is that it was running lean at idle, and much and much leaner at higher RPMs (19.x+).
I've adjusted the idle mixture to make it run much richer at idle to start with. However, it's still goes to 17.x+ at higher RPM.
Since it goes from rich to lean depending on the RPM's, I suspect that both Impco's have completely different idle mixture settings causing them to run "out of sync".
What would be the best way to tune them identical? I doubt that counting the number of turns on the idle mixture screw is anything near exact.
I saw someone on the internet stating to close one air valve so the system will run on one 425, allowing it to adjust that 425. But sounds a bit weird to me, although it might work.
I'm pretty sure there are people here with more expensive of knowing to adjust twin 425 .
Thanks!