What's the relative gain on each? I thought I remembered from somewhere that skipping a tooth was about 8 degrees.

 

Skipping a tooth will give you the ability to add more timing if needed. If I didn't end up parting my truck out I was going to skip a tooth just because I wanted a little more timing then I could get out of it the way it was.

 

That sounds approximately right, Jason. I thought I heard 10* or so. I'm not sure how many teeth are on the gear again. I think 720*/# of teeth would give you the amount of timing relative to the crank angle. I say 720* since the crank turns twice for the pump to turn once.

Anyway, according to my possibly backwards math, a 72 tooth gear would yield a 10* bump per tooth.

 

So if you did jump the timing a tooth, could you bump it back down kind of like retarding the timing and turn the timing down a bit cuz it'd already be really advanced for already being jumped, and then bump it back up when you wanted/needed?

 

Yes. I think rotating the pump either way will only be a couple of degrees. If I knew the radius of the middle of the gear to the edge of the timing mark, and how much the timing mark can move before it hits the head. I could figure it out with a little calculus. But you can skip a tooth, then rotate the pump AWAY from the head to make it a softer bump in timing overall.

 

Hmmm......better be careful with the baby bottle!

 

When I jumped my timing I was in kind of a rush to get the truck onto the dyno, so I didn't check the actual timing or how much jumping a tooth moved it. What I did do was set the truck at TDC, put in a timing indicator, zeroed it, jumped the timing, and then moved the pump to put the timing indicator back to zero. I did this so I could get back to my baseline if I didn't like how the truck ran. Turned out that the stock match marks lined up, the pump was shoved to the head before the jump.

 

How much more power do you reckon you made with the jump?

 

I seem to recall a tooth is 12°. Although what Dzl Damon says seems more accurate so maybe 10° is closer. The equivalent to 12° is an 1/8th inch when pushing the pump towards the head.

I don't want to sound like a know-it-all, but I've been learning about this in school so I thought I'd share. For those who don't know, we want combustion pressure to peak when the piston is around 15° to 20° ATDC on the power stroke. 15° is when there is the most lever advantage. Anything before that is going to give greater bearing wear and higher stresses on the conn rod. Anything after that and leverage is going to steadily diminish.
Of course, by increasing the amount of fuel it's going to take more time to burn it, and the faster the rpm, the smaller the window to burn it all. So timing is super important to get it just right. As Josh Ayers said in your 'who's going for the record' thread, he's spent a lot of time over the winter tuning, and not much time bolting stuff on.
I don't think timing gives us more 'power' as such. I think it just adjusts how we harness the potential heat in the fuel we burn.

 

Timing will increase horsepower, especially to the mid to higher rpms . This happens for the same reason you mentioned, the window for injection and burn is smaller at higher rpm. Therefore, you advance the timing some to compensate, ESPECIALLY if you are injecting more than stock fuel levels and ESPECIALLY if you have larger than stock injectors. You will make more horsepower (at higher and mid rpm), but you will loose some peak torque numbers. Obviously you know that horsepower is a function of Torque related to rpm. Since your torque peaks at much lower RPMs, and you compensated timing for mid to high rpm, you will loose out some down low.

 

Ahh, this makes sense. Like I said, I'm learning this. I ain't no master! Thanks Dzl_damon!

 

Interesting. . . .

Currently, my mess has jumped two (2) teeth and has the stock/OEM marks lined up. As such, it doesn't clatter. It does clatter with the KSB energized when tipping into the throttle (light load). Checking that arrangement by the book with a micrometer presents with 2.8mm plunger lift at TDC of #1 (Stock/OEM had it at 1.4mm plunger lift).
It runs normal as best I can tell with DD. Mid and upper RPMs are lively.

I'm thinking of backing it off a little for a run or two this Thursday and see what changes with the turbos (more heat in the exhaust gases for the turbos) and how it performs.

 

How big are your injectors David? I hear larger injectors require the extra timing to be "normal". I've heard as much as 30* timing (or extra timing?) or something crazy on some of the big pulling trucks....

 

JQmile said somewhere around 40° advanced on the big pullers . I guess the tractor guys are around there somewhere too. He said those guys are injecting more fuel than they can burn in order to keep the pistons cool. That's pretty hard core right there!

 

Scheid 6x.016" EDMs.