Carb tuning - need some quick advice

[ascuro]

Hi again - today I decided to replace my plugs, wires, cap, and rotor...so I tried my hand at something I haven't done in years - tuning a carb =)

It's a crate GM 350, edelbrock 1406, in a 70 blazer (and I'm just outside LA, at about 1000 ft elevation).

The best manifold vacuum I could get was almost 19" Hg, at around 600rpm. I backed the mixture screws out a bit, and ended up at 1 1/4 turns out - does that sound borderline too lean? I just don't want to damage my pistons and such.

Another thing is - my idle is somewhat unstable...it drops about 50-100rpm every so often, but my manifold vacuum stays rock steady. And I mean zero movement in vacuum whatsoever. Any clue what could be cause this?

 

[Hogback Fabrication]

You will not damage your motor at idle, no matter how lean you have it running (the tiny amount of fuel you are burning cannot create enough heat to hurt anything). I wouldn't worry about the slight difference in idle as long as the engine runs well otherwise. The change in idle can be attributed to changes in outside temp and atmospheric pressure (i.e. if a storm is moving in the pressure changes), or some other general carb inconsistency.

 

[blazerguy 90]

Did you replace the fuel filter ?, if not try that it might help your idle, a plugged fuel filter will give you a rough idle miss.