I set my timing at 15.5* what should I expect?
 

And will my HG be O.K.?

15.5* is pretty conservative, it should be fine.

John

Should I get an increase in mileage?

My running temp on the freeway @ 65 is 500-550F

your mileage may increase a lil bit but don't expect miracles...your egt's should drop....engine will clatter slightly more...crackling /popping will be gone durign cold starts in the winter....and popping will be gone at higher rpms.....it will rev up smoother without stumble at higher rpms......truck will feel peppier ...kinda like it lost weight....engine will feel "lighter" as it revs...thats the feeling I can describe when I had it done

I need mine done bad... ;(

Any long term effects? Bad?

DB:

Glad to see you got the #10 in. With that in the stock position and being your only fuel mod you will be fine with the 15.5*. Mr T gives a good description. It will sound as if the engine doesn't have to work as hard when cruising down the road.

Only long-term bad effect is that it might leave you wanting more [laugh].

Seriously, 15.5 is very conservative and will keep you and the HG safe. I would however, strongly consider the 3K GSK as a next mod. It doesn't necessarily add more fuel but lets you use all that you have better.

Paul

I don't think so, especially with the conservative amount you bumped it up. The stock timing is quite a bit below what is "optimal" in order to reduce emissions. I think its NOx emissions that go up as timing is advanced but I'm not sure. I went from 13* to 17* and noticed an immediate improvement in throttle response. It also took noticeable less throttle to keep the truck at highway speed. Plus the throttle response is much better and there is a lot more "top end" in the motor. I haven't filled up since I had it done so I don't know what improvement I'll see in the fuel mileage department.

John