HsOffRoad

Hello guys, first post here.

First and foremost, kudos for the great forum. I've read many of your posts since I bought my first gen a few weeks ago, you guys have a wealth of useful knowledge.

That said, I'm about to pull the cover to tab my KDP and loctite the cover bolts. While I'm in there, I'm thinking about advancing my pump timing one tooth, and am looking for some real world input.

Searching through the forum, I've found a fair bit of info about advancing VE pumps one tooth at the gear - the most useful (for what I'm doing) being this thread where Crossy's Son and Archer39 discuss their experiences towing with roughly 10* of timing advance:

https://www.dieseltruckresource.com/forums/advancing-ip-one-tooth-question-t270520.html?

I've got the basics down - Stock initial advance on an I/C 1st gen is around 12.5*, 1/8" timing bump brings it up to around 16 or 17*, each tooth jumped on the gear is 10*, and if you run one, the M & H spacer is worth around 10* on the top end (which accomplishes the same thing as milling 4mm off the end of the advance piston). Stock cam timing is "O" to "E", and one tooth advanced is "O" to "C". I also know that generally speaking, the more fuel you are dumping into the cylinder, the more timing you can run (up to a point, due to spraying outside the piston bowl, washing out the rings, etc.), and that most guys recommend a 1/8" bump (roughly 16-17* initial timing) for otherwise bone stock trucks.


So here is where I need actual, real world input for my setup:

I know from the above post that guys like Archer39 are out there succesfully towing one tooth advanced with the pump at the stock marks (roughly 22.5" inital timing), but accoding to his sig, he's running injectors that are quite a bit larger than my stock I/C injectors, and I don't know if he's running the stock head gasket and bolts, or if he's got his truck o-ringed, head studs, etc.

Even though I'm running the stock injectors, my truck is definitely fueling a good bit more than stock. It's got a Denny T AFC delete on it, the 366 spring, the full fuel screw cranked up a fair bit, a piston lift pump swap, drilled out banjos, BHAF, FS1221 fuel filter, and 4" open exhaust setup.

My question is, with the stock injectors and above fuel mods, can I advance the pump gear one tooth and still tow safely, or am I better off running less timing?

You know how it is... you spend a half hour reading online, you'll see 100 posts warning about how you're guarateed to destroy your head gaskets with anything more than 16* of initial timing advance, but then you see people like BC847 running 2 teeth advanced on the pump, the M&H spacer, and the pump bumped on top of that (which is probably going on 60* of total timing advance).

My gut instinct says that jumping one tooth can't be that bad (even on a stocker), since Cummins specs that alignment ("O" to "C") for all of the earlier non-emissions motors as stock from the factory.... but you guys may tell me otherwise.

My truck gets used for occasional towing (5K-10K lb. trailers, nothing to crazy weight-wise, but when I do tow it's often in the mountains), and general daily driving duty. I'm not looking to make the truck a hot rod, I just want the thing to make decent power, pull hills well, and keep mileage reasonable. I have a pyrometer, and I'm plenty comfortable with having to keep an eye on the gauge and back out of it if temps start climbing. I don't plan on using the M&H spacer or modding the dynamic advance system in any way.

So bottom line - With my fuel mods and stock injectors, can I safely advance the pump gear a tooth and keep the pump at the stock marks and still tow and keep my head gasket together with the stock gasket and head bolts? And safe or not, will I benefit from having the extra 10* of initial timing or am I better off sticking with the typical 1/8" timing bump?

I appreciate the input, and sorry for the long post.


-Hans

1972RedNeck

If you jump a tooth, how far away from the head will the pump go?

HsOffRoad

The pump is currently set at stock timing (lined up with the stock marks). As it sits, it's about dead center in the adjustment slots, which means it could be turned quite a bit in either direction. There's probably enough room to get it back close to stock timing after the tooth jump by pulling it away from the head if I wanted to, but that's not what I'm going for.

What I'm trying to find out is if it is realistic with my setup to leave the pump at the stock marks and advance the gear one tooth, giving me 10* additional advance (which will be right around 22.5* initial advance).

I know it can be done and tow safely if you go to bigger injectors, but I haven't found any info about jumping a tooth with just pump mods, retaining the stock injectors.

Basically, I'm trying to determine if it's worth doing.... Will it be safe and offer an improvement in mileage/performance, or is 10* extra advance too much for the stock injector sticks, even with extra fuel? Is it going to cause problems like blown head gaskets, hard starting, etc?


-Hans

HsOffRoad

Anyone?

No one has tried bumping timing 10 degrees with stock injectors?




- Hans

93-12Smoke

There was a post a couple months ago about a guy claiming to make like 400hp on stock injectors and a lot of timing.

My question is why go that much on stock injectors? Your bottom end is going to suck!

archer39

I am still running the same exact setup I was when I that post came about. I tow more than I did then also. As far as I know the head gasket is still good. This is without o-rings or studs.

I would think you would be fine advancing it a tooth. How much do you tow?

c12h26

Im running 1 tooth and pump to the head with stock injectors

HsOffRoad

In theory, it should be good for close to a 2 mpg jump in fuel economy. Plus it will help clear up some of the low-rpm smoke from the AFC delete. Going off what guys who run their trucks a tooth advanced say, I don't think the effect on bottom end power should be all that noticeable (but I may be wrong). A one-tooth bump should be similar to running with the KSB on (like if you have it hot-wired to a switch), which is barely noticeable on a stock truck.



This is what I was hoping to hear. I only tow maybe once a month for a few hours at a time. Usually around 5,000 lbs, but never over 10,000. I do tow in the mountains though, where they have some long grades. Does your truck have hard-start issues in the cold or run hot (coolant wise) in the summer?



Good stuff. Is the truck a daily driver or a track toy? Ever try towing anything like that? Are they intercooled or non-intercooled injectors? Any noticeable loss in low-end power? Any head gasket issues or hard starting when it's cold? Overheating in summer?



Thanks guys,


-Hans

archer39

Starts right up and the temp is right where it should be.