Calif. emissions

[85stepeide]

I drive a 85 chevy truck. The motor is a 300hp 383. The cam is 204/214, 401/420, heads are ported chevy 883's, intake is performance products dual plane, and edelbrock tes headers. All the temp/vac sensors, and all the smog lines and pump are hooked up and working. All the parts are CARB approved, so I dont have any trouble with somg testing. The carb is the stock rochester it came with. The motor runs great, BUT it does idle a little ruff, and I feel there is a little more top end too. I plan to up grade the carb to recipe #1, Im sure that will give me what Im looking for. NOW for the question, how will upgrading the carb to #1 specs. effect emissions, when I get the car checked?   

[Shark Racer]

Where does your car run RPM wise on the dyno tests?

My setup is approximately recipe 1 for the mains but more like recipe 2 for the idle circuit due to a slightly aggressive cam with pretty low static CR.

I passed fine, although I was a bit rich and was *close* on the 15mph test. Both tests were just under 1400 rpm. I think I may have gone a bit overboard on the idle circuit for smog purposes.

If you're running the test at closer to 2000 rpm, you should be able to curb emissions through APT adjustment.

It really depends on where you are right now - if the carb is running real lean (15.5+) off idle, then going to a slightly richer idle circuit should improve NOx and HC. However, if it's close to stoich you'll start jacking up the CO.

That cam is pretty mild, so you should be OK on smog. What section of CA are you in? I'm trying to find more QJet heads in my neighborhood (Mountain View)

[Cliff Ruggles]

Not enough camshaft or head flow for big top end power.  882 heads are very restrictive in the runners, and porting isn't going to help them much.  The 204/214 cam would be done very early in the RPM anyhow, in a 383 engine.

Should make a great low to mid-range engine, with smooth idle and strong torque to about 4000rpm's or so.

You should be seeing smooth idle with good vacuum, what is the carburetor number and what has been done to it?.......Cliff

[85stepeide]

Yes you are right. My truck does have GREAT bottom and mid range. The carb is 17085266, I think thats the carb that belongs on it. I did rejet it but that was six years ago, and I dont remember what I used. Otherwise the carb is stock. The motor runs great but idles like crap. Also you can see from the dyno sheet the hp drops off at 4500 then picks up at 4800. After reading your book, I figure recipe #1 should fix thoes issues. My concern is after I fix the idle circut, will I still be able to pass CA. emission testing?
C:\Users\Frank\Pictures\2013-04-18 dyno sheet\dyno sheet 001.jpg

[Shark Racer]

I have gone *very* aggressive on my idle circuit and still passed CA smog, as mentioned above. My idle circuit is more like recipe 2 if I remember right. .038 tubes and .059 DCRs.

I went from 55 DCRs to 59 DCRs and that took me from a little too lean to a little too rich.

[Cliff Ruggles]

Should be idling great with stock idle settings.  I'd pull the idle tubes and clean them up or replace, and check the size.  Unless they have been removed, they may be plugged up some, causing the rough idle.

The power curve is EXACTLY what I'd expect for the combination of parts.  882 heads are very restrictive in the exhaust ports, designed for emissions, not for performance.  They work best with dual pattern camshafts, and best suited for low rpm applications.......Cliff

[85stepeide]

The carb was purchased 6 years ago from a national carb rebuildeing service. I dont think it has any kind of modifications. My truck has always had a ruff idle. After the first smog test, the smog tech told me the carb was lean, thats when I went to a little larger main jet, but dont remember what I used.  The change did help with cruising and mid range, but still a crappy idle. After 6 years the carb is starting to leak, and the choke is starting to stick ,so now is a good time to rebuild and fix the idle. Ill check the idle tubes, what size do you suggest I use.   

[Shark Racer]

Step 1 is to make sure they can flow. In the book, Cliff has some suggestions on tube sizes. Look at the section on performance upgrades to the idle system.