1959 carter idle query

[MY 59]

hi again, looking to borrow on everyones experiences as usual

when I first got my Caddy the motor etc was in a pretty sad state
all has been rebuilt and freshened up and I put a kit through the carb (Carter AFB) myself.
I am more familiar with Holleys, but this carb was very simple and an easy rebuild (seems a damn good design actually).
what I am finding is that to acheive idle I must 'load up' the fast idle screw and open the primary throttles slightly (like a 'normal' carby) and once satisfactory idle RPM is reached then adjust air and fuel mixtures, or the engine stalls due to critically low RPM
according to the manual etc the throttles should be fully closed and the idle system is just the air bleed and 2 fuel mixture screws.

Anyone got any ideas???
very tempted to whack a 1405 or similar Edelbrock on, which is basically the modern version of this carb anyway, but if I can redeem the original that would be great

thanks again

[Dan LeBlanc]

I wasn't totally happy with the idle on my 61 either with a Carter so I got it dialed in just a little better.

Factory specification is 480 RPM in drive.  I can get the 61 to idle down that low, but it really isn't happy there.  Many say that with modern fuels, idling that low is not reasonable.  600 in park is where I'm at right now and the engine is fairly smooth.  I'm also at 7.9 degrees advance on the timing to compensate for modern fuel, so a low idle isn't that practical with that either.

The key is not to try and get your idle down to where it should be in one fell swoop.  It needs to be stepped down gradually.  Turn in the idle screw a half turn or so, then adjust the air/fuel mixture at each step down.  I use a vacuum gauge - turn in the air mixture screw on one side until the engine starts to stumble and back off and tweak until I get the highest reading on the vacuum gauge, then repeat for the other side.  I'll do this a couple times before cranking the idle down a bit more to make sure I'm ok to get down to the next step

[INTMD8]

I had the same problem after the rebuild of my 59 but thought it was because of the slightly larger camshaft I installed.

I was able to get it to idle but had to open the air bleeds so much they were actually very loud and annoying.

I welded another step onto the fast idle piece so the idle screw was still functional with the choke off and set the idle at 600rpm.

[Jon S]

You can bring the idle up by advancing the timing a degree or two.  I find these cars run best at about 8 - 10 degrees advanced as opposed to the 6 degree Factory recommendation - could be the fuels today. . .

[INTMD8]

Good point. I'm close to 20deg initial, mid 30's total with mechanical advance limited. (But again, not an original cam)

[MY 59]

Thanks for the responses everyone
I also installed a slightly larger Isky cam so perhaps that combined with fuel, age and wear are the reasons
Good to hear people,have experienced the same thing and good to hear Jim is using the fast idle screw the same way I am having to

Thanks all