Hercules

I'm going to advance the timing in my truck listed in my sig...hopefully I'll get some time before fall to do it. I'm only going to bump it to 15 or 15.5 degrees. According to what I've read/heard, that seems to be a universally agreed safe setting for everyday use. I thought I've heard that among other benefits from advancing the timing, bumping it up will also increase mpg. Those of you who have advanced yours, did you notice if your milage increased or decreased and by how much? Also, I'm going to install the 3K spring kit while I have the truck sitting still long enough to do the timing. Thanks for the information and any suggestions if something other than 15 -15.5 degrees is recommended.

infidel

I got about a 2 mpg empty increase after bumping both my trucks to 15.5

first4age

I bumped mine to 16.5 and notice 2 mpg improvement.

I recently changed the fuel filter and notice another 2.5 mpg improvement on highway mileage. The best I got before was 18 mpg. After fuel filter, I got 20.3 mpg.

Hercules

Thanks for the info. I'm glad to hear it helps mpg. I've never really complained about mpg with this truck...I usually get about 18 mpg loaded driving in city/suburbs. I was worried that bumping the timing could cause the mpg to go the other way and give me a reason to complain.

Now it's on to having to replace yet another brake line that let go tonight. I wish I had the time to replace all of them at once.

robert chilton

Just remember to check the timing now. Just in case it has been changed before. That way it can be put back if MPG is affected, which I dought. My last tank was 20.22 MPG running empty. Good luck.

bmoeller

Never saw any mileage change. Just a bit more responsiveness and 150* cooler EGTs. Went from the stock 14* to 16.2.

Hercules

Yours was stock at 14*? I don't know what the stock timing is for other pumps, at least I forgot, but, I think my 215 pump is stock at 12* or 12.5*. I'll have to check the tag on the pump tomorrow to see. I do plan on checking it "mechanically" before making any changes. If not for any other reason than to simply see where it's been running at and how close to stock it has remained.

I've heard that you don't want to go over 16* with stock head bolts and gasket. That's why I was thinking about going to 15* or 15.5*.

Also, one more question. Does advancing the timing effect ease of starting?

2500

got my 97 set to 16.5

have not measured for mileage due to mainly burning waste oils.

Tate

The more timing you run, the harder it will start. That being said, my 24v is set to where you are wanting to set yours, and it lights up right away.

If you're looking for mileage, check your fuel pressure. My 12v was getting terribly mileage when I picked it up. Put the FP gauge on it, it was 14 psi at idle and at 2k rpm. I put the bic pen spring in the over flow valve, now its at 40 psi, and I'm at half tank where I would normally be filling it up. Haven't gone a full tank to see what I'm actually getting, but it has improved a good bit.

2500

hmmmm... replaced mine with a new overflow value from cummins dealer. may have to try the bic pen spring trick.

will take fuel pressure reading first... what should stock pressure be?

infidel

Normal fuel transfer/lift pump pressure specifications are 17 - 22 psi at idle and 25 - 35 psi at 2500 rpm no load.
More is not better as it can blow out internal injection pump seals or even crack open the fuel filter.

2500

thanks for the spec's and tips!

bmoeller

Yep. That is what the tag said.

I'm still running a stock h/g and bolts. Timing at 16.2*

Never saw a change in startability. Go much over that (17+) is what I've heard you'll start having more trouble. Also depends on the h/g thickness or otherwise making changes to lower the compression so you can run higher timing. That is one reason why you see the "big boy" pulling trucks plugged in and using ether to start when it is over 90*.

Willdsl

Only thing I've heard is you have to keep your foot out of it to gain the MPG. Not easy to do with extra power. Makes you want to have fun with it.