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post #1 of (permalink) Old 12-20-2000, 04:38 PM Thread Starter
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Could a carbbed small block w/cats pass emissions?

Hi Guys,

I'm considering going chevy small block [img]/wwwthreads_images/icons/tongue.gif[/img] in the YJ this summer. The 6 is really marginal with the added weight my Jeep has put on over the past few years. (tire carrier, winch, hardtop, rear jamboree rack coming up) I could go AMC 304 or 360 also, and mount it easily to the 999 auto in my YJ (as I understand it), but I've heard the AMC v-8s with the distributor hanging off the front of the motor ain't so great, and honestly I don't know that much about them. (I know plenty of you will tell me they are great motors [img]/wwwthreads_images/icons/smile.gif[/img])

I'm fairly familiar with the chevy smallblock from my old chevy impala days, rebuilding and playing with a bunch of 283s, 327s, 350s, etc.

Do you guys think that a small block chevy, in good shape, carbbed with a quadrajet for good off-road ability, using a GM HEI perhaps, with a dual exhaust, and twin generic catalytic converters (one in each exhaust) but no other emission parts, would pass a dyno emissions test?

I don't have a visual here in Massachusetts, but they just instituted the dyno a year ago, and I would need to pass. I'd prefer to stay away from injected motors, as I don't know much about those either, and really prefer the simplicity of a carburetor and a basic fuel pump.

Any thoughts?

I know it's kinda a general question, just looking for opinions. [img]/wwwthreads_images/icons/crazy.gif[/img] My 999 and 231 are kinda old too, at 200,000+ miles, but still run great, so a motor/tranny swap would be considered too. What's the best way to go?

Thanks,
Pete [img]/wwwthreads_images/icons/smile.gif[/img]

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post #2 of (permalink) Old 12-21-2000, 09:12 AM
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Re: Could a carbbed small block w/cats pass emissions?

Well I'll give it a jab. As far as I know.....The emission tests that I have seen look for COx and NOx stuff. The NOx stuff can be cleaned up real easy with a good cat. conv. The cat. conv. can also help a little with the COx stuff, but mainly the fuel atomization system determines how much COx stuff comes out, as a direct result of the air/fuel ratio and how close it can stay to it. Now if you run a carb and a cat. conv. you need some sort of a system to put freah air into the exhaust to help complete the burning process before it enters the cat. conv., otherwise you'll burn up the conv. in a short time. If you run a fuel injection unit then it and its associated sensors and electronics should keep the fuel/air ratio tight, thus not allowing much unburned gas to to go out the tailpipe. Now as far as the dyno, "they" just started that here in NJ. 1981 and newer have to go on it, 1980 and older just get a tail pipe check. That translates into having the idle, cat. conv. and vacuum systems tuned up. Period. Nothing else comes into play. I'm assuming that all other factors are at optimum, such as plugs, wires, cap, and engine not billowing blue smoke. Also logic must dictate that if "they" have the specs. on how much emissions your vehicle spits out, through the vin number, then they will also know what volume of emissions come out. Now adding two more cylinders one would think that this would increase the volume by 33%? Since your "they" don't have a visual, If you could clean up a small block that is 33% larger or more than your original engine to the emission standards of your original engine you should be good to go and "they" would be none the wiser. I think you're looking at the f.i. setup with one or two cats. and even still it might be good enough. See if you can find out the limits in the different catagories for your engine and compare to say a Camaro with the 5.0 over a couple of model years. If the Camaro's numbers are in line with yours then look for a wreck and get everything necessary for the conversion. Better yet look for a wrecked Chevy or Jimmy 4wd. and get eng/trans/xfer case. If your engine has the computer controlled BBD, then your chances are better. If it has a factory f.i. setup then maybe not. I'm sure somebody here has been down this road???? Maybe they can offer some insight for you. The later 700R4's seem to be good for off road use and have an overdrive for the street to boot. The adapter to your xfer case might be pricey...also get help with that here. Try doing a search here for that one. Good Luck....

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post #3 of (permalink) Old 12-21-2000, 11:50 AM
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Re: Could a carbbed small block w/cats pass emissions?

[img]/wwwthreads_images/icons/crazy.gif[/img] Er....YEAH...what Jimmy said..[img]/wwwthreads_images/icons/crazy.gif[/img]...the anthoprobe hooks to the glenditer and that forces the zoobie to uncrud.[img]/wwwthreads_images/icons/crazy.gif[/img] [img]/wwwthreads_images/icons/laugh.gif[/img] I'm fairly certain that this setup would need both the EGR and the Air Injection to pass. Saturday a guy came over with a '78 GM FS 4X4 that he just bought. Half the stuff was missing, headers, and NO EGR, but here he had a clean smog certificate. That just proves that there are still a few "Smog Coyotes" operating out there if you can just FIND one[img]/wwwthreads_images/icons/tongue.gif[/img].

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post #4 of (permalink) Old 12-21-2000, 12:06 PM Thread Starter
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Re: Could a carbbed small block w/cats pass emissions?

Thanks for the input guys. [img]/wwwthreads_images/icons/smile.gif[/img] Jimmy's theory is interesting, especially since the dual exhaust would only measure one of the 2 pipes (I've never seen 2 hoses at the inspection station [img]/wwwthreads_images/icons/crazy.gif[/img]), and thus it would only measure 4 of the 8 cylinders. It's probably a % thing though - % pollutants in total amount of tailipe emissions, so that wouldn't matter much. ?[img]/wwwthreads_images/icons/tongue.gif[/img]? If it were "amount of pollutants per mile" or something, that may have a benefit.

Thanks guys - I guess maybe it's time to learn about this new-fangled "injection" thing, eh? [img]/wwwthreads_images/icons/crazy.gif[/img][img]/wwwthreads_images/icons/frown.gif[/img] Maybe I should just buy an older Jeep [img]/wwwthreads_images/icons/laugh.gif[/img] and do what I want with it. [img]/wwwthreads_images/icons/smile.gif[/img] I will likely learn a lot when I take the weber and HEI equipped YJ to the dyno for a sticker this weekend... [img]/wwwthreads_images/icons/crazy.gif[/img]

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Re: Could a carbbed small block w/cats pass emissions?

[img]/wwwthreads_images/icons/smile.gif[/img] You know, Pete; fuel injection was a dark mystery to me too until Larry Van Every spelled it out line by line in a way that was so logical that it made perfect sense....open loop...closed loop.....in a lot of ways it's simpler than some carbs, and OH THE BENEFITS! I MIGHT be able to lay my hands on that write up if I did a little looking around. Perhaps LEVE might see this post and respond.[img]/wwwthreads_images/icons/wink.gif[/img]

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post #6 of (permalink) Old 12-21-2000, 05:22 PM
 
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Re: Could a carbbed small block w/cats pass emissions?

Hey Pete,
The guy I bought my axles from had an '86 CJ with a carbed 304, dual exhaust, two cats and no other emissions equiptment. He told me he passed MA tail pipe emissions no problem. This was before the dyno though.
I have been doing extensive research on a FI'd engine swap for my CJ and right now it looks like the best choices for V8's are either the obvious Chevy 350 or Ford 302 HO,351. I have no prefrence really, but I have been finding about 5 EFI Fords for every one EFI chevy.
If you want a V6, I have been also finding a ton of TBI Chevy 4.3's which also look like good swap material. Many people seem to like them and the TBI injection seems much easier to wire and supply fuel to.
I also have a line on a couple EFI 4.0l's here in MA. Let me know what you are thinking about. Since I am also going to travel down this road in the spring.

-C

'79 CJ-7
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post #7 of (permalink) Old 12-22-2000, 10:39 AM Thread Starter
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Re: Could a carbbed small block w/cats pass emissions?

Hey Chris,
Yeah, I guess we'll wait and see. The YJ goes on the dyno tomorrow, so I will hopefully learn a lot about what goes on with that thing. [img]/wwwthreads_images/icons/crazy.gif[/img][img]/wwwthreads_images/icons/tongue.gif[/img]

Thanks everybody! I'll tell you all how I do.
Pete

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