1st Generation Dodge Cummins 89-93 Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with Rotary Injection Pumps

Timing bump

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Old Apr 27, 2010 | 08:53 AM
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Default Timing bump

i was going to bump my timing but im shy bc i dont want to go to far. if i loosen the bolts and push the pump to the head is that too much? and wat is the cons of bumping the timing?
any input will be greatly appreciated!!!
 
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Old Apr 27, 2010 | 10:19 AM
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thats what i have done on my 1st gen and cons it probably will effect your egt's some mark it and go 1/8 to 1/4 inch and see if that helps and just go from there
 
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Old Apr 27, 2010 | 01:03 PM
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About 3/8" on the dampener equals 6* timing at the pump. Make a marker wire pointer and measure 3/8" of rotation. Of course, you are backing up your engine (counter-clock-wies) to increase timing. Did my 96 that way and it runs GOOD.
 
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Old Apr 27, 2010 | 01:57 PM
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It will lower your egts but raise cylinder temps.
 
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Old Apr 27, 2010 | 02:17 PM
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it will run better
 
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Old Apr 27, 2010 | 09:38 PM
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so then just loosening the 3 bolts and pushing it as far as i can to the head would be WAY to much, okay. i think i am going to bump it an 1/8th, and what do ya mean by it leaves to much heat in the cylinders?
 
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Old Apr 27, 2010 | 10:12 PM
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1/8" is perfect for most trucks. Less if you tow heavy.

More of your fuel is being burned in your cylinders and holding more heat on top the cylinder.
 
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Old Apr 27, 2010 | 11:47 PM
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Originally Posted by BIGREDGOAT
so then just loosening the 3 bolts and pushing it as far as i can to the head would be WAY to much, okay. i think i am going to bump it an 1/8th, and what do ya mean by it leaves to much heat in the cylinders?
Timing is more a factor of piston speed (piston speeds up when rpms are high, but injector spray takes same length of time) and needs to be advanced to get the entire spray done before hitting TDC. Advancing it too far, just sprays down the walls of the cylinder and can even pre-burn before the piston gets all the way to the top of the stroke, as the spray pattern is cone-shaped, and the sooner you spray it, the wider the cone.

This also effects certain types of injectors, such as marine 370s, which have a wider angle of spray (155* versus street injectors of 145*) causing excess smoke and fuel consumption. Though it is possible to make more power, it is "dirty power" at a cost of excess smoke and wasted fuel, not to mention the potential for diluting the oil supply from fuel washing down the cylinder walls.

Unlike gasser motors, our rpms are usually fairly low (most power is done before 3200 rpm -- gassers are just getting warmed up at that speed!). That means that we do not need the same static timing as do higher rpm motors, nor does bumping past a certain point actually help produce "more" power. It gets as good as it gets, then starts getting worse. About 16.5* "seems" to be the max that a close to stock engine can hold. Conversely, the Dodge factory specs of around 10* (or less if the pump gear has slipped) means that we're not getting what we should from the engine. Finding that happy medium, where cylinder pressures are at a good peak, without getting too high, is key to best power and efficiency.
 
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Old Apr 28, 2010 | 08:16 AM
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so i make a mark and measure an 1/8th of an inch then line em up and she will purr?
 
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Old Apr 28, 2010 | 09:41 AM
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Originally Posted by BIGREDGOAT
so i make a mark and measure an 1/8th of an inch then line em up and she will purr?
Make the mark on the balancer. Rotate the engine backward until the pointer measrues 1/8" travel. Tighten the pump gear. Purr....

I did mine with the timing cover off, but no need to go to that length to set timing this way. Also, since doing it, I've procured the correct tools to check my results via the #1 DV with the dial indicator. I'll do so one of these days when I have everything apart and see just how close I got with the simple method.

Oh, and just in case you screw something up, you can go back to factory timing very simply by using the timing plug that us under the big cap on the side of the pump. Pull off the cap (loose a little oil that is inside the pump -- don't worry, it refills once the engine runs from engine system oil pressure) -- flip the little peg with the groove backward -- align the pump so that the foot fits exactly into the groove in the peg -- timing is set to factory specs. Articles detailing this are on-line. I think Geno's has one in their database of articles.
 
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