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| need help bypassing lean burn https://slantsix.org/forum/viewtopic.php?t=17912 |
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| Author: | 81dodgepickup [ Mon Jun 05, 2006 10:19 pm ] |
| Post subject: | need help bypassing lean burn |
My newly aquired 81 D-150 hesitates and stalls on acceleration. Mechanic says the lean burn or S.C.C. is bad. Previous owner says intake manifold has a leak. I would like to replace the intake and exhaust manifolds, and do away with all the emmisions control on this slant six. Can someone advise me on what parts to buy, will I need to replace the distributor ect. The truck currently misses and stalls on acceleration it also smells of gas. |
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| Author: | 74.swinger [ Tue Jun 06, 2006 3:51 am ] |
| Post subject: | |
The best way to replace the lean burn is with an msd box. 6a has no rev limiter 6al has a rev limiter. Either are sufficient for a street car. ________ Alaska Medical Marijuana ________ Swed |
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| Author: | Sam Powell [ Tue Jun 06, 2006 5:38 am ] |
| Post subject: | |
You may not need to replace the manifolds, but if you need to, a good way to go would be to replace the intake with a two barrel set up, either aftermarket, or stock Mopar unit, and put a set of Dutra Duals on. One of the problems with the stock slant is that the design calls for the intake to be slightly loose when it is cold so the long cast iron manifold can expand as it warms up. If you make it all too tight, the exhaust manifold is likely to crack. Once it is warm, it is tight, but that makes the car somewhat prone to bad drivability when cold. The Dutra manifolds are split in two, so you can tighten them down without fear of things breaking with the expansion and contraction. Do a search and see if you can find a post about where to buy them. In the past Docter Dodge,(Doug) from time to time has them for sale. You will have to have a couple of custom header pipes bent, but it is worth the effort and expense. You will find the two barrel set up gives you better performance, and better mileage. On my Dart, I installed a stock 340 exhaust system with the Dutra manifolds. I had the exhaust bender, ( who advertized in Hemmings) simply leave the front bends from the tranny cross member forward unbent. Then I cut that off, and finished the job with custom bent pipes. In another post, ask which two barrel is best. I had my favorite which was a Carter, BBD, but I haven;t thought about carbs much since I went EFI. |
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| Author: | Reed [ Tue Jun 06, 2006 6:39 am ] |
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The easiest and cheapest way to bypass the SCC is to go to the HEI conversion. Do a search on this site to find out how. You will have to replace the distributor, but you will also most likely have to spend some time fine tuning the advance curve on the distributor, unless you find one out of a similarly geared truck. The only emissions item which when deleted will really give you any performance increase is the EGR valve and OSAC valves. A properly functioning catalytic and AIR pump don't hurt performance and really clean up your exhaust. It sounds like your computer as well as your carburetor are worn out. I also vote for a Super Six with a BBD two barell carburetor, but you should only have to replace the intake manifold. Swapping to a two barrel is another topic that has been covered before. Search the site. |
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| Author: | Matt Cramer [ Tue Jun 06, 2006 6:41 am ] |
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Well, there are several right answers for how to replace a Lean Burn ignition. The thing about Lean Burn distributors is that they have no provisions for timing control. None whatsoever. It's all built into the computer. Consequently, if you're ditching the computer, you will need another means of timing control. Replacing the Lean Burn distributor is not the only way to get timing control. It is simply the cheapest, easiest, and most foolproof option. So, here are some possible combinations: 1. The HEI method, probably one of the cheapest performance ignition modules around. Use a stock-type electronic distributor with vacuum and mechanical advance with HEI module. I think you can use the stock coil with this - someone please correct me if I'm wrong. No ballast resistor required. 2. Copy the pre-Lean Burn system. Use an electronic distributor with built-in advance, Mopar ignition module, and ballast resistor. 3. The MSD black boxes method. Keep the Lean Burn distributor. Get a MSD programable timing computer, MSD-6 box, and matching coil. MSD isn't the only company that makes ignition control black boxes - you can also get them from Crane and Bowling and Grippo / Megasquirt. They aren't cheap, but you must have some sort of external timing control device if you want to keep the Lean Burn distributor. |
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| Author: | SlantSixDan [ Tue Jun 06, 2006 7:07 am ] |
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Quote: The best way to replace the lean burn is with an msd box.
Naw, it ain't.  MSD box = needless expense and (lately) spotty reliability.The HEI conversion is a great deal less costly, much easier to carry a spare brain for, and is capable of ignition performance well in excess of what any street-driven and many raced slant-6s need or want. |
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| Author: | Doctor Dodge [ Tue Jun 06, 2006 8:03 am ] |
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And another way to do the conversion using the Chrysler ECU and parts: http://www.slantsix.org/articles/leanbu ... rticle.htm DD |
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| Author: | 81dodgepickup [ Tue Jun 06, 2006 9:23 pm ] |
| Post subject: | |
Thanks all. I will pick up a hei and new distributor, (there is a 79 truck in the junk yard, would this distributor be better than one from ebay?) |
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| Author: | Reed [ Tue Jun 06, 2006 10:07 pm ] |
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I say go for the boneyard distributor. It will be far cheaper and the advance curve will be closer to what you want for your truck (provided it is the original distributor). Just make sure the vacuum advance pod works and the drive gear is intect. |
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| Author: | 74.swinger [ Wed Jun 07, 2006 3:54 am ] |
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Quote: Quote: The best way to replace the lean burn is with an msd box.
Naw, it ain't. MSD box = needless expense and (lately) spotty reliability.T Around here every one and their brother uses an msd box on their dirt track car. My 440 swinger starts quicker,idles smoother and seems to rev quicker than it did with the mopar orange control unit. Here in the rust belt the barely adequate wiring these cars came with 30 years ago is usually suffering from corrosion and high resistance. This is one reason why I like the msd. I use none of the factory wiring. A reman distributer should be cheap at a parts store also. ________ CHF50 ________ Weed |
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| Author: | emsvitil [ Wed Jun 07, 2006 4:12 am ] |
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Quote: A reman distributer should be cheap at a parts store also.
Reman is a dirty word around here........ 
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| Author: | SlantSixDan [ Wed Jun 07, 2006 7:46 am ] |
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Quote: I had not heard of the reliability issues. What is that about? they building boxes in china now or somehting?
Or something. MSD for many years made rock-solid reliable hardware, but in the last four years or so I've been hearing an increasing number of grumbles about dead boxes.Quote: My 440 swinger starts quicker,idles smoother and seems to rev quicker than it did with the mopar orange control unit.
I don't doubt it at all. But you get the same quicker starts, smoother idling and better running with an easier and less costly HEI swap.
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