Holley 4160 idle and surging problem on a 3.4

[warmonger88]

I just rebuilt the carb a few days ago, and I haven't been able to get it to run right since. I need to find out how to tune this thing specifically for the 3.4 in my S-10. It wont idle cold at all. I have to keep the RPMs around 2k for about a minute, then it will idle on it's own. Also I noticed it surges a little while I'm driving, and there is little response initially pressing the gas. I really don't know much about carbs. Also it has an electric choke.

[geoffinbc]

After the rebuild did you set the floats? With the choke on, the throttle lever should be on the high idle cam and you should get a 1500RPM or so idle. Go to Holleys website and print out the applicable setup guide. It will walk you through adjusting the idles speed and jets. All this should get you back to normal.

I would suggest a wideband O2 sensor for adjusting idle mixture, part and full throttle fueling. Did this to my father in laws car and it made a big difference in performance and response and an even greater difference in fuel economy. No more wasted fuel out of the tail pipe.

[Purple pit]

2cfm per cubic inch on a highly modded engine. 600cfm is way too much for a 3.4.

[geoffinbc]

Where did he say it was 600CFM? 4160 is a series number. Most feature electric choke and a vacuum secondary. They have a metering plate without jets, power valves or accelerator pumps. They are easier to tune than a full feature carb.

CFM also has as much to do with operating RPM as it does CI.

[warmonger88]

I set the float level a little low because one of my bowl plugs was lost by the previous owner. He had a bolt in it with thread tape and it leaked. I got my new ones in last night so i can bring up the float levels because they were sort of rough set. I'm idling at about 1400 RPM when it's warm, but it just really doesn't like to idle cold.

Where did you get the wideband o2 sensor?

[pocket-rocket]

You can get them all over the net. Ben also sells them. You would need a laptop with you to read the a/f ratio if you get one without a gauge.

http://wot-tech.com/shop/gm-60v6/innovate-lc-1-standalone-wideband-controller/prod_293.html

[warmonger88]

If I bought that kit from WOT-Tech, I think that would be the most sophisticated part on my truck.

[pocket-rocket]

That's going to be pretty much any wideband setup, though.

Sent from my HTC One X using Tapatalk 2

[geoffinbc]

Just get an Autometer wideband gauge. Comes with everything you need. It is one of the best things we ever did on my father in laws car. You know instantly if something if off with the carb. You don't need a laptop or special tools.

The KIT that WOT Tech is selling is not a gauge. I am talking about something like this. http://www.autometer.com/cat_gaugede...earch&gid=4058

[Arns85GT]

If you have a 600 cfm the basic problem on the primary side of the carb is the metering for idle. The 600 is way too fat for the 3.4 engine. You want the 390 cfm. It will flow properly for the displacement and your idle problem will disappear. The 390 rebuilds come set up for a 5 liter engine though, so you have to jet down some for the smaller displacement and you'll want a light accellerator pump cam.

On my 2.8 I actually run #51's on the primary side, with a .31 shooter on a 1/2 cam setting to make the accellerator cam shoot 1/2 a shot (25mm) This is how I had to do it to avoid a bog. On your 3.4 this setup will leave you just a little lean but it will idle and run fine. You will likely end up with about a #54 on primary as well as secondary. Hope this helps

Arn