http://www.slantsix.org/forum/viewtopic.php?t=13264
knock your self out
just not your engine
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| distributor recurving? https://www.slantsix.org/forum/viewtopic.php?t=25935 |
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| Author: | gato [ Tue Nov 20, 2007 5:33 am ] |
| Post subject: | distributor recurving? |
where do i find info on doing this? i thought i read there was some in the articles section. i don't see it. D~~~! |
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| Author: | 68barracuda [ Tue Nov 20, 2007 1:27 pm ] |
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http://www.slantsix.org/forum/viewtopic.php?t=13264 knock your self out just not your engine
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| Author: | walpolla [ Tue Nov 20, 2007 1:42 pm ] |
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hello, gato,if you want to email me, I have a 16 page article on the subject. I ca'nt get it to post here - wrong format or something. but I can email it I think. regards,Rod 
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| Author: | Aggressive Ted [ Tue Nov 20, 2007 5:59 pm ] |
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Also check out the timing post on this page. |
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| Author: | Aggressive Ted [ Tue Nov 20, 2007 6:00 pm ] |
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Also check out the timing post on this page for recurving info. |
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| Author: | Sam Powell [ Wed Nov 21, 2007 4:33 am ] |
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Ems, If you are following this, I read the entire thread linked here, and printed it out. Quite an amazing amount of trial and error research there with carefully recorded results. The question is, how did the car drive with the different curves? How did it feel to the foot, and seat of the pants? I know that is alot to ask. What generalities about degrees of advance can you offer;not what springs to use. What advance numbers would you program in at various RMS and vacuum readings if you coud simply do so with a computer spead sheet? Thanks man. And lastly, and probably most difficult for many reasons, do you know how winter weather would affect those numbers? Would you have a different map for Winter and Summer? I know Winter is only a theory to you. Sam |
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| Author: | emsvitil [ Wed Nov 21, 2007 8:55 pm ] |
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Quote: Ems, If you are following this, I read the entire thread linked here, and printed it out. Quite an amazing amount of trial and error research there with carefully recorded results. The question is, how did the car drive with the different curves? How did it feel to the foot, and seat of the pants? I know that is alot to ask. What generalities about degrees of advance can you offer;not what springs to use. What advance numbers would you program in at various RMS and vacuum readings if you coud simply do so with a computer spead sheet? Thanks man.
Being able to just do a curve on a computer would have made live simple..... And lastly, and probably most difficult for many reasons, do you know how winter weather would affect those numbers? Would you have a different map for Winter and Summer? I know Winter is only a theory to you. Sam What I noticed was that ignition advance at the lower rpms (idle - 2000/2500) was the most noticable. More advance seemed to make things snappier, but I needed to compromise and back off the lower rpm timing due to pinging at slightly higher rpm (limitations of a mechanical system) that couldn't be adjusted away with springs. With the computer you could have the curve do anything you wanted. Another thing is the vacuum advance. I get a lean surge at lower rpms. It occurs after the choke would be off, but before the engine is fully warmed up. Another thing that you could probably adjust away with temperature sensors. And finally under warmer weather I occassionally notice a slight ping that doesn't occur when it's colder (really need a little less advance) When you're close to what is a good timing curve, it is actually hard to tell the difference, you're really just trying to avoid pinging at that point.... |
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| Author: | 68barracuda [ Wed Nov 21, 2007 11:18 pm ] |
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Quote: Another thing is the vacuum advance. I get a lean surge at lower rpms. It occurs after the choke would be off, but before the engine is fully warmed up. Another thing that you could probably adjust away with temperature sensors.
Same experience over here - but are using holley 465cfm 4150 - surging started after I installed a 7.5 powervalveAnd finally under warmer weather I occassionally notice a slight ping that doesn't occur when it's colder (really need a little less advance) When you're close to what is a good timing curve, it is actually hard to tell the difference, you're really just trying to avoid pinging at that point.... I have not yet touched my vac advance will play with that tonight and see |
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| Author: | Aggressive Ted [ Thu Nov 22, 2007 9:38 am ] |
| Post subject: | Timing Map |
I experienced the same thing while changing springs. Let's just leave the carb and temperature out of the equation for a moment and make that a constant. If you over advance at 2000 to 2500 where there is still a significant load but high torque it will surge. My particular build will not ping, but it will surge when backing off on the throttle or when the vacuum is above 15 pounds. I like the low end punch and midrange snap I get from the lighter springs but need to limit the overall advance at that point where there is still allot of load. To be safe you should be around 35 degrees and as the load decreases and the vacuum increases after 2500 or so let it advance on up to 60 degrees, but not over because again at 3000 rpm I would feel a surge when vacuum reached 20 pounds. I tried several attempts at richening the carb to eliminate this effect, but it would not go away. The only fix was to reduce initial timing from 20 degrees to 16 degrees. The V8 11R vacuum can has alot of throw and was just coming on a little too much. I can still run my favorite #57 jet in the 1920 Holley Economaster, burn the tires and not ping and still get good mileage. Sam, I would not make a linear map, but design it so you get the bottom end punch and midrange snap with the right springs but limit timing to around 30 to 35 degrees and as the load decreases and vacuum rises slowly extend the timing advance on up to at least 45 degrees if not 55 or more to get the mileage and lean burn. I am trying to do this with a heavy looped spring and the 11R vacuum advance. You could dial it in allot quicker on the computer. If the climate is hot, then everything needs to be reduced all along the curve equally by a factor of 4 or more. My tests were done this past summer in the Pacific Northwest on 90 degree days with high 75 to 85% humidity. |
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| Author: | Slant6Ram [ Thu Nov 22, 2007 12:07 pm ] |
| Post subject: | This is an article I compiled a few years back. |
http://www.potentialtech.com/pmoran/dist-9-22-05.pdf Still never got around to adding pictures, but actually, I still hope to do so for a future article in the slant six racing news. |
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| Author: | walpolla [ Thu Nov 22, 2007 4:51 pm ] |
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thanks for making that article public. I will have to increase my computer skills to find out how to get it into the forum friendly format. thanks.Rod |
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| Author: | Slant6Ram [ Sun Nov 25, 2007 4:13 pm ] |
| Post subject: | Readable format |
I published in the PDF document format because it is one of the free and universal formats for viewing and printing (ever tried getting a web page to print pretty from every browser) A pdf document can be read with adobe acrobat reader (a free download) on any of the windows platforms and there are free pdf readers for unix, linux or mac. Sorry to make it troublesome for those who have not used PDF before, but it is a widely accepted way to publish online documents. |
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