1970 Cdv 472 Idle?

THE1ANDONLY · #1 (**permalink**) 01-26-07, 07:30 PM

Wondering What My Idle Should Be At(rpm's) On My 1970 Cdv 472; Also Should I Have My Timing Advanced A Degree Or Two For Better Performance?(i Have Removed All Things To Do W/smog, If That Makes Any Differance To The Idle/timing Or Not?) Any Info Would Help. Thanks

davesdeville · #2 (**permalink**) 01-29-07, 02:38 AM

Idle should be 550 or 600 in drive IIRC, I'd recommend an HEI swap so your timing won't change with wear, for better performance, and for not having to screw with points..

BluEyes · #3 (**permalink**) 01-30-07, 07:50 AM

Your '70 shouldn't have had anything smog related except for the vacuum advance being stopped in the lower gears. Anything else you pull is going to hurt the driveability and/or mileage.

Be sure the vac advance is hooked directly to a source of ported vacuum and you're good. Stock timing is 7.5*, and I can't remember if I've bumped mine or not. I think it may be at 10* but not sure.

Idle rpm is 600. You can tune it using the 'best idle' method with a vacuum gauge or using the proper lean drop method (somewhat harder). The lean drop gives a bit better mileage but needs a more accurate tach. From the sticker on my '70, you turn the idle mixture screws all the way in, then out six full turns. Set the idle rpm to 620 on a warm engine, then turn in one screw untill the RPM drops to 610rpm. Finally turn in the other screw untill the RPM's drop to 600.
I've actually gone to using a similar technique on all my carb'd cars - it gives better mileage, a bit better throttle response down low and there is no change in full throttle power.