98regency

Hey everybody!

I've some issues with the emissions of my 307cui with a quadrajet and I found something interesting in the internet. I searched my serialnumber of the carb in the internet and found that my carb was mountet on a 350 engine. Are there any differences between the carbs of the 307cui and 350cui engine? exp. jets, metering rods etc.? The problem is the HC-value (Hydrocarbons).
It's too high and I tried evertything to fix this value but no way. Also interesting is, that the value at idle of 500-600 rpm is too high, but at idle of 1300 or more perfect. Don't know why.


-98regency-

droldsmorland

The 350 Q-Jet carb in stock form will (should) be richer than the stock 307 due to the difference in its metering rods, jets and some other adjustments as well as internal passage architectures. The rich idle is a function of the carbs idle circuit and engine architecture plus poor A/F distribution at idle. You didn’t mention what the failing HC levels is now and what the govt. requirement is. If its slightly off you could possibly reduce the HC emissions with proper jetting and careful tuning (Air fuel mixture, ignition curve tuning, plugs, wires etc...) Read your plugs and exhaust pipes.
You may be able to obtain the desired results by re-jetting and installing the matching metering rods.
You may want to find the correct carb for your application and tune the engine per the factory specs in order to pass emissions so long as nothing else has been modified (cam, intake etc...as you don’t mention any modifications)
If you’re a DIY person buy Dog Roe and Cliff Ruggles Q-Jet books. Most everything you to know is in these bibles.

98regency

Ok thank you for your answer. Yes I'm an DIY^^ and I already have Doug Roes Q-Jet book. But I didn't found any informations about the factory jets and metering rods for my carb.
The intake manifold is from factory and the ignition correct. The predecessor of my car adjusted the ignition from originally ~15° to 6°(!). So he reached the specified values for the emission control. But with 6° the engine ran bad.

jcdynamic88

i'll never understand why emission testing was done at idle,it should be more important what the emissions are while driving and I don't see how the jets or metering rods can affect idle mixture,that's what the idle circuit/mixture screws are for.

98regency

There are jets for idle mixture in several sizes. Like the main jets. So you can also adjsut the mixture of idle.

joe_padavano

Because proper testing under load requires a dynomometer, which is obviously a significant investment. Here in the US, emissions testing shops are required to have them, for exactly the reasons you cite. The reality is that ANY emissions test done is only a spot check. This is why a visual inspection of the equipment is also required. The federal standards require testing at cold start, idle, and a drive circuit. They also require evap system testing. None of this is done by test shops, as the time and cost would be prohibitive. The required emissions testing is intended to be a go/no go test, with the assumption that if you pass the tailpipe sniff AND the equipment is hooked up correctly, the car will meet the standards. It's not perfect, but it's a compromise of practicality and thoroughness.

droldsmorland

If you google Quadra-Jet carbs there are several vendors who can guide you with tech support as well as provide you with correct parts. The Carburetor Shop, JET, Cliff Ruggle. to name a few good ones. They offer rebuild services as well. Buy Cliff Ruggles book on Amazon. It has info that Roe doent have & visa versa.

98regency

Done! Going to read that book and hope I will find the right informations. Thanks!

98regency

So. First I found was the information, that the carb on my enigne was built for an buick engine.
My carb number is : 17080249

The 7th number typically indicates division application and "4" denotes Buick.
Carbs built for Olds engines were denoted by number 5.
Maybe my carb is not factory mounted. Now I want to find out, which carb number was factory mounted on my engine, but this is very difficult, because Oldsmobile doesn't exist anymore :S
Perhaps anybody can help me?

-98regency-

98regency

Does anybody know which carbs were factory mounted on 1981 98s with 307cui engine?
The identification number has to begin with 1708125x.
It's important for me pls help :/

-98regency-

olds 307 and 403

Did you try adjusting your mixture screws? Another guy had the same issue and that did it. Turn the screws in to point it idles a bit rough. That might be enough to pass. Adjust back after leaving the shop.

98regency

Hi
Yes, I tried to adjust the mixture screws, but it doesn't work. I want to have the factory mounted carb on my engine.

nsnarsk65cutlass

This maybe true in some states but here on the left coast they do evap leak testing as of 2007 as part of the biannual smog test for vehicles 1976 thru 1995.Visual, egr function,tailpipe emissions are also required.If in the city dyno test,in the foothills 2 speed test.Back to OPs question high Hcs passing COs indicate a lean condition.Nick

turbobill

Is your car emissions exempt becuase it is an export? If so, the carb on yours may not be the electronic feedback carb use here in the states for '81.

98regency

My car were assembled/mounted here in Switzerland trough the GM Corporation of Switzerland. But the parts were made in USA. The carb is non electronic (without TPS etc.).

I decoded the identification number of the carb and it says that the carb were from 1980 and built for Buick motors. I think this matters.

My carb number is: 17080249

And I decoded with the carb book of Cliff Ruggles. And he descibes in his book, thaht there are differences between carbs for olds, buick pontiac etc.

Like this ---> http://www.cliffshighperformance.com...carb_ID_2.html

-98regency-

turbobill

The only year your carb (for a 307 Olds) was manufacutred here (in the US) was for the 1980 49 state US & Canadian (and maybe Mexican) cars. 1980 California and '81 and later US 50 state were all feedback carbs. Canada and other countries probably used the same non feedback carb as what is correct for your car for 1980. Later than 1980 from other non emission countries (like your country) would probably also work.

1980 was the first year of the 307. The 1975 through 1980 carb from a 350 Olds, 1975 & 1976 455 Olds, and 1977 to 1979 403 Olds would also work but the calibrations are quite different (primary jet size, primary and secondary metering rod size, secondary hanger, power piston spring tension and secondary air valve spring tension). Those things can be changed to make a 455, 403 or 350 carb more suitable in calibration for a 307.

There is a good chance the 1980 350 carb (last year for the 350) would have the same number as the 1980 307 carb. For a non feedback '81 and later carb, it's a needle in a haystack. For some years after 1980, GM continued to ship lots of non feedback, US emissions exempt full size cars to the middle east, so there may be the correct '81 carb there.

Buick never used a Q-Jet on a 300 or so cubic inch engine so the calibration on your 1980 carb is probably for the 350 Buick V8 (only Buick V8 that year) unless it was changed by whoever installed it. Pontiac used a non feedback carb on some of their 1980 Q-Jet equipped 301 V8's but the choke and fuel inlet are probably different.

The Olds and Buick used different choke heating arrangements, however, those things can be switched from carb to carb. That's more than likely the way the Buick carb was installed on your Olds unless the choke heating system was cobbled.