Emissions Help

[ROOK1]

Ok guys and gals I need a little help. I took my '71 with a 28/36 DHSA2 on a 1600 in for an emissions test today and it was an epic fail (so they say).

High Speed test: HC (PPM)----CO%----CO2%----RPM
--------Standard----700 ------- 5.00-----N/A-----2522
--------Reading-----333 ------- 8.33 ---- 8.7
--------Deviation---367 ------ -3.33
--------Result-------Pass--------Fail
Idle Test
--------Standard----700 -------- 5.00-----N/A-----1087
--------Reading-----341 -------- 2.69 ---- 11.1
--------Deviation---359 -------- 2.31
--------Result-------Pass--------Pass


I came home to see if there were some adjustments I could make but it doesnt really appear that there are besides changing jets or mixture "valves". I can see in the barrels that there are some jets there and there are 2 "screws/valves" on the outside by the float bowl. I didnt mess with the jets but I did take out these "screws" and I found something that could be the problem. The screw on the primary barrel had a 70 stamped on it and the secondary had a 50. I compared this to a carb Denise had sent me a while back and hers was the opposite. I decided to reverse mine and here is what happened. The idle dropped drastically and it now pops when I get off the gas but it definitely seems to run better.
Could this have been the reason my emissions were off so bad? Any suggestions you have would be greatly appreciated.

[mdrburchette]

A high CO reading is most likely unburned fuel, so was your car running a bit rich? Check your plugs and see if they're carboned up or wet. If swapping the jets made it pop through the carb, then that usually indicates a lean mixture. I would definitely check/change the plugs and make sure you're not running rich. An ignition tune up might help as well, such as replacing the points, condensor, rotor and cap.

[ROOK1]

I have already replace the cap, rotor, points, condenser, plugs and wires. It was popping through the exhaust not the carb. They did say it was running rich and I have had alot of black soot on the tail pipe.

Are there internal jets (in barrels) and external jets (more like needles) on thee carbs?

I swapped the external ones but I dont know if it was the right thing to do. I just matched them to the way they were in the carb you sent me. I did nothing with the internal jets. What shoud I look for if I pull them?

I guess my main question is what jets should be in which barrel? Will this help my issue? Is there any other adjustment available to me?

Thanks for the reply.

Chris

[So Cal Mark]

As rich as your car is running, you need to diagnose the cause before you start changing jets. The jets you see from the top are air bleeds. The main jets are inside the float bowl.
What speed was the high speed test done at? Was it on a dyno or merely just holding the throttle open?

[ROOK1]

As rich as your car is running, you need to diagnose the cause before you start changing jets. The jets you see from the top are air bleeds. The main jets are inside the float bowl.
What speed was the high speed test done at? Was it on a dyno or merely just holding the throttle open?

2522 RPM. Just holding it open with a sniffer in the pipe.

I am trying to get help diagnosing the cause on this forum. The only reason I changed the jets on the side of the bowl was because Denise had sent me an old carb a while back that appeared to be un molested so I decided to look at what was in hers. Hers also had a 50 and a 70 but they were on different sides (primary secondary) than mine so I thought I would give it a try.

What do you think the cause may have been to get a reading like that on the high rev?

[So Cal Mark]

a 70 idle jet is huge, I'd put 50s in each side for the test. What size air jets are in the carb? Is your air pump working?

[ROOK1]

I dont believe it has an air pump unless it's inside the engine. It's a '71 with a 1608. I'll swap in 50's and Ill get back to you on the air jets.

[So Cal Mark]

sorry about the air pump question, I hadn't gone back to look at the beginning to check year/model. What size air bleed is in the primary side?

[ROOK1]

OK here's what I have. There is a 195 on the primary and a 150 on the secondary.

I may have discovered the problem. If not THE problem definitely a problem. I found these 3 tasty little cheerios in the secondary barrel.



I would think they would restrict air flow creating a rich situation. Sound right?

Mark, let me know what you think about about this setup.

Idle jets: Primary 50 Secondary 50. Current set up as directed by you. Going from P70/S50

Air jets: Primary 195 Secondary 150. No change from test.

Additional info. It has a header, supertrap muffler and aftermarket air cleaner and blockage removed.

Thanks,

Chris

[So Cal Mark]

secondary has no effect during a smog check unless the stop screw is adjusted to keep the throttle plate open. You might need a larger air jet in the primary for the test

[ROOK1]

Mark,

I found this site with parts to order but I am now more confused than I was to start.
http://www.weberjets.com/index.php?opti ... 0&Itemid=2
I see Air Corrector Jet, Main Jet, Idle Jet and Emulsion tube. I assume the Air Corrector Jet is the one you mentioned to change. Do I need to do anything with the Emulsion Tube and Main Jet(s)? What is your recommended Air Jet size?

'71 1608 header, supertrap muffler, aftermarket air filter other than that stock as far as I know. Also I am testing around 4800ft in elevation.

If you stock these parts I am more than happy to buy them from you.

Chris

[mdrburchette]

Chris, I found a break down of the 28/36 DHSA carb specs in my factory manual. Maybe this will help you:

[ROOK1]

Thanks! I now know I am waaay over my head on this one. I know of the idle jet and air metering jet (I think), but I havent a clue about main jet, main air metering jet, pump jet, power jet, power air metering jet or power mixture jet.

Anybody have an FI system they want to sell? It's got to be easier to retrofit that than work on a carb.

[mdrburchette]

Chris I sent you an email asking if you want a copy of the breakdown for your car. It'll show you where to find all those jets. Hope I sent it to the right Chris.

[ROOK1]

Thanks Denise!