Ok, I'm back to looking at late model D150's, and those generally come with leanburn (unless otherwise removed). From what I can tell, when it's working good, there isn't much benefit from going to a non-leanburn conversion; is that correct? And on a bad leanburn setup, there's plenty to be gained upon conversion... and of course, once one starts changing camshaft/carb/exhaust/etc, then something that allows for adjustment of the timing advance is very desirable.

I don't have an FSM (yet); but from what I've read of the setup, there should be a vacuum sensor (transducer), throttle position, coolant temp, an oil pressure (maybe that's just for choke?) and finally ignition (presumably for engine speed and crank position). Are these sensors still commonly available? Seems to me that if I am only after a stocker, then repairing a faulty setup is less work than a conversion to non-leanburn.

[From a very brief look, it appears that the Holley 6145 electronic feedback carb was for CA emissions; Fed emission vehicles were still 1945. The 6145 adds a more complex carb with potentially harder to source, more wear prone parts (the parts that are constantly moving for a/f mixture adjustment), and also the setup comes with an O2 sensor. Not sure yet if I want to mess with that setup or not. Albeit that the 6145 may "live with" the cat better, due to actually controlling a/f ratio.]

Finally, just to confirm what I'm thinking: leanburn or not, it should have minimal impact on the catalyst's life, correct? I mean, timing would have to be way off will lead to early death (stumbling, missing, poor running). But otherwise, this leanburn system doesn't control the airpump (if it has one), correct? [Not sure I'm interested in rodding out a cat at this time, much less removing one, regardless of state emissions laws.]

Thanks.

Feedback with O2 sensor is way, far, much more compatible with a catalytic converter than non-feedback carburetion, but the 6145 is a tiny carburetor that makes the engine as wheezy and impotent as an 80-year-old lifelong 3-pack-a-day cigarette smoker. Here is what I would do with a feedback-equipped slant-6.

As for Lean Burn: Well, anything that reduces the dirtiness of the exhaust coming out of the manifold makes life easier for the catalytic converter, but the feedback system does the lion's share of pre-catalyst exhaust cleanup.

There is no crank position sensor, and no oil pressure sensor. Also no throttle position sensor in the sense that we know them now in the fuel injection age. Some repair parts are still available; others are tougher to find.

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I can't figure out how to link to the post, but Reed's picture http://www.slantsix.org/forum/viewtopic ... t=leanburn here shows a connection to the oil pressure location; plus I coulda sworn I had seen "oil pressure" sensor indicated here http://www.allpar.com/mopar/lean-burn.html but it appears I'm wrong on that. Maybe the oil pressure is just to indicate engine is running? Or maybe it's strictly to control the choke.

No crank sensor, got that; but rudimentary crank position can be derived from the ignition trigger, for at least TDC (or however many degrees advanced you're supposed to time it to). Crank position, TDC, not sure what you want to call it in this system.

I missed that the throttle position sensor, though. I wonder how allpar's page is off on that? Unless if it's going purely off MAP? Hmm... I'll have to get that FSM and figure out how they did that. Just as well: pot based positioning systems tend to be short lived. Hall is much better...

I have to admit, if I was really worried about emissions, I'd go EFI. I don't think I could justify the cost, nor the amount of time to tweak such a system into operation. I just don't want to go disabling emissions systems in search of dubious power/mpg gains, simply because I couldn't troubleshoot issues.[/url]

I guess it depends on the emissions testing for your state. If there aren't any or they aren't rigorous, I would remove the lean burn setup, catalytic converter and install a Holley 1945 and forget about messing with it.

Holley 6145 kits are expensive and/or incomplete. No one wants to mess with them. Finding another decent working 6145 is nearly impossible or just outragously expensive. No one really knows a whole lot about them.

The good part about owning an older vehicle with a carb is that YOU get to decide how you want it to run. Lean, rich, smooth....you are capable of adjusting it the way you want. With a 6145 you are at the mercy of the lean burn system. There is hardly any adjustability to it. If your truck is running rough, you can normally smooth it out with a timing adjustment and/or mixture adjustment with a Holley 1945. You don't get that with a 6145. What if its running a little rough because there is a small vacuum leak at the throttle shaft? Now you have a carb leaking air that needs to be rebushed and most carb shops wont touch a 6145. If they do they usually charge as much as a new 1945 + head pipe without cat would run you.

You can only troubleshoot these things so far before you just give up because you are at the mercy of the system. There's a reason why everyone removes them and its not because they are just lazy. It's because they are expensive, it's hard to find parts, they don't run well even when working correctly and you can get better mileage and power with a regular carb as opposed to the feedback system.

I'll have to figure out what to do, or, what I am willing to do. Truck that I looked at is minus cat already; dunno about the AIR system (likely altered somehow also). The laws are a bit ambivalent about this: NH state law says that the cat is required on anything 20 years and newer (and of course, '96 and newer have to have all OBDII readiness flags set); but Fed law says "no removing that cat!"

So, I'm not quite sure what I want to do: I'm under the impression that, w/o a feedback carb (or EFI), reinstalling the cat is a losing proposition (unless if I have rigged up with one of those "test" pipes--AKA, install cat for the one day of the year it's required...)

Sounds like I am much better off ditching the Leanburn though; and maybe swapping from 1945 to 1920. Looking around I find few people advocating dealing with Leanburn, unless if absolutely required; since I don't have a sniffer test (and hardly any visual inspection) it sounds completely worthless to bother with.

I will have to consult a wiring diagram to give more details, but I know that in the 80s Chrysler routed the (+) feed for the carb choke pulloff spring electric assist through the oil pressure sending unit. If you unplug the oil pressure sending unit wire the electric assist on the choke pulloff spring no longer works. As to why the Lean Burn component diagram lists the oil pressure sending unit as a component of the lean burn system I have no answer. I have successfully removed lean burn systems from a slant six powered van and a 318 powered Fifth Avenue and neither vehicle had the lean burn wiring directly tied in to the oil pressure sending unit.

Lean burn really isn't worth messing with unless you absolutely have no other choice. The best thing about the lean burn system is that it already has no ballast resistor in the ignition wiring and you can use the (+) feed for the lean burn computer to trigger the relay for the HEI ignition system swap. Your vehicle will run smoother, burn cleaner, have more power, and get better MPG if you remove the lean burn system and replace it with a standard carb (in good condition) and a standard electronic ignition (HEI is my preference).

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I'd also argue they are worth messing with if you are working with EFI but don't want to get too exotic with your ignition system. But for a daily driver, I'd only leave one there if it was working really well.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
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Can you expand on how a lean burn ignition system makes working with EFI easier?

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Casually looking for a Clifford hyperpak intake for cheap.

I know the Leanburn distributor can be nice for EFI--if the EFI controller is used to control spark, that is. The Leanburn distributor lacks advance, so the ECU can control timing advance instead.

Precisely. Spark control is a bit easier with a locked distributor, and the Lean Burn is a cheap and straightforward way to accomplish this.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair