I have a 96 12v a/t with 218K. I have a few mild mods planned (fuel plate, gsk, exhaust and maybe injectors). If I bump the timing to 15 or 16, will the change be noticable? Any downside?
Thanks and take care.

 

If your timing is stock and not slipped, not a noticable change seat of the pants.

Downside, maybe a little louder at idle and loaded.

Otherwise, it's a necessary step to a good running Cummins.

Ronnie

 

OEM timing sets the torque band in the useable towing\hauling\work range ~1800rpm, while limiting power in the upper range ~2200rpm - increased timing improves power output in the upper rpm ranges, but also moves the torque band upwards toward 2000rpm and above - you get more racing power = horsepower, but less working power = torque - plus, to really take advantage of it all, you'll need to increase governor rpm limit and replace the low-rpm valve springs to prevent valve-float in the higher rpm ranges.

Just the B4\after plate and adjustments will totally amaze you, even without timing changes.

 

If you bump your timing to 15 deg. you will notice engine is a little smoother running. The more timing the higher in the rpm will be maxamum torque but to go to 15 is not that much so you will move your torque peak very little. 15 deg. is about as much as you want if you pull all the time, in my opinion. The more timing you have the more your engine will feel like a gas engine. I agree that you should probably want to put in a 3k gsk. but you will not need valve springs unless you like to run up around 4k rpms. I run my truck at 15 deg. timing and I like it much better than the 13.5 it was stock. You will also see a modest improvement in fuel milage too. I think I pull a trailer with my truck more than I drive without one and I think 15deg. works well with the auto trans and towing. One other thing I would advise is to put in a toggle switch to lock and unlock the tc. there are times when you need to be in o.d. with the tc unlocked to keep your rpm in the sweet spot(1800-2000rpm) for towing. Also if you go on a lot of low speed back roads towing a trailer it is nice to have the truck in 2nd gear and lock the t.c.(keeps the trans oil temps lower)