Edelbrock carb issues...

[geezer#99]

Originally Posted by Mrturner1

NOT USING THE 4 MIDDLE INTAKE BOLTS???!!!

you have a vacuum leak.

Look at the pic Matt!!
Tell us where you don't see centre bolts!!

[57taskforce]

Out of curiosity how are you checking your Rpms? I've got a couple of 1406s. Both my 3100 and my K/20 have one, and they both run very well. my K/20 was having problems getting hung on the fast Idle cam. When it's warmed up and choke is off you can open the throttle a bit by hand and at the same time push down on the cam linkage and make sure its all the way down so the fast idle is off. I'd go over The Whole intake with carb cleaner and see if you can find any vacuum leaks as well.

[B. W.]

Originally Posted by Spedy7

Quick update, think I've got it near where it needs to be. It turns out it's not the carb (who would've figured that lol). Unplugging the vacuum advance leads to a lower rpm - swapped in the heaviest springs I got and it's better - rpm drop is still oddly high. As it sits it'll idle at 1000 just fine and in gear it'll go from 700 and slowly creeps down to 550-600, doesn't really sound like it's struggles ether (some vibration, but doesn't putter). Could probably use some springs that start the advance at 1200 rpm though.

1000 is still a very high idle, it possible you're into your transfer ports at this point. You may have a nice vacuum leak, spray your base gaskets like 57taskforce suggested. Also how it slowly creeps down - that could be a fuel pressure issue like geezer said. (fuel pressure is pushing past the needle, not noticeable at higher RPM's)
Are you getting any change when adjusting your mixture screws? It's possible you're huntin' several rabbits: vacuum leak, fuel pressure, timing issues, etc.
Also, I learned "never tune a dead horse". Confirm your engine is sound first. How much vacuum is the engine pulling? Do a compression test, verify correct cam timing. When I have an issue like this I back off, slow down & start with the basics.
there are a lot a guys here with a lot of knowledge, we're throwing a lot of ideas at you but they are all valid points.

[RichardJ]

>>Tell us where you don't see centre bolts!! <<

They are in there! I had to blow the image up to be sure. They're RED!

[Spedy7]

Can't mess around with it today, but I'll grab a can of carb cleaner tomorrow, it does look like the base gaskets might be leaking. No change in idle when adjusting the mixture screws, I got them turned out 1 1/2 turns. Cut the throttle spring down so it's much tighter now, throttle stays shut and not partially open. The engine is a fresh rebuild that's still breaking in (around 480 miles on it) and still working out the kinks (like this issue). Set the initial timing to 14* and tinkered with the carb with vacuum advance unplugged, plugged it in and tinkered with what i felt needed to be adjusted. I got a tach to check rpm.

On a side note: did GM offer these trucks without heaters too? Looking at adding a/c in the future and I don't even have the holes for the heater setup.

[57taskforce]

If it has a heater delete there will be a plate bolted to the firewall coving the opening for the heater box. There will be a delete plate mounted to the dash to cover where this controls would normally be. If you have a complete, real heater delete they are extremely rare and there are people looking for them on this board. As for your carb base gasket, if it's leaking or there are any other vacuum leaks the idle mixture screws will likely do nothing because of the air being sucked in thru the leak.

[Spedy7]

Originally Posted by 57taskforce

If it has a heater delete there will be a plate bolted to the firewall coving the opening for the heater box. There will be a delete plate mounted to the dash to cover where this controls would normally be. If you have a complete, real heater delete they are extremely rare and there are people looking for them on this board. As for your carb base gasket, if it's leaking or there are any other vacuum leaks the idle mixture screws will likely do nothing because of the air being sucked in thru the leak.

I'm 100% certain it's a real heater delete, no signs of hacking or cutting and no fresh air hole ether. Any other information about this?

[57taskforce]

http://67-72chevytrucks.com/vboard/s...d.php?t=527393
Here's a little bit, there's lots of threads on it if you use the search.

[Spedy7]

Swapped in a pair of lighter springs and little bit of a loose throttle cable (other one got too uncomfortable), still not acting right. Carb wants to stick open just a little still - smacking it brings the idle back down where it should, like the floats or metering rods are sticking. Also not seeing much fuel going through the filter...so that's one problem.

Also, I was wrong, someone just hacked the hell out of the dash when they replaced it and welded a panel over the old holes :/.

[geezer#99]

Can you adjust either mix screw all the way in without the motor wanting to quit?

[Spedy7]

Originally Posted by geezer#99

Can you adjust either mix screw all the way in without the motor wanting to quit?

Yup, as far as it can go.

[geezer#99]

That tells you that you're idling on the power circuit.
The cure is closing the primary throttle enough to cover the transition slot.
Turn your idle down.
If it struggles to idle slowly then increase your timing a bit and adjust your mix screws for the highest idle.
There's a section here about the transfer slot. It's for a holley but your carb is the same.
http://www.crankshaftcoalition.com/w...EI_distributor

[Spedy7]

Originally Posted by geezer#99

That tells you that you're idling on the power circuit.
The cure is closing the primary throttle enough to cover the transition slot.
Turn your idle down.
If it struggles to idle slowly then increase your timing a bit and adjust your mix screws for the highest idle.
There's a section here about the transfer slot. It's for a holley but your carb is the same.
http://www.crankshaftcoalition.com/w...EI_distributor

Wow, that might just be it. Set the initial timing to somewhere around 18* (my marks only go to 16*) and followed with lower idle speed and out of the box mixture settings. Idle doesn't fluctuate anymore (from what I can tell) and the trans isn't slamming into gear. Only problem (I guess?) is I set it to ~900 rpm, so it drops to around 650-700 in gear and slowly creeps down to a bit above 500. Some rattling, but no stuttering or anything (wouldn't really call it smooth ether, probably a mix in-between). I want it at a steady 700-800, but that would require an idle of 1400 or so in park. Think I might need a small external fuel pump and pressure regulator too.

[88fordf150]

Vacuum leak? Bad PCV valve?