HR climbs as the runs get longer

I know zip about physiology, but based on reading/listening to people who do have some education and expertise, I've learned that it's called "cardiac drift" and is normal.

HR creep, it happens.  You experience less of this in the cooler months compared to the warmer months as the body's cooling is much different.  To cool yourself the body increases the blood volume at the skin, in turn you're sweating more and blood volume becomes denser, all adding to the HR increase at the same work effort.

I'll typically start my long runs in Z1 range and by the end of my run I'll be at upper Z2 to Z3 range.  In the summer the rate of change in HR is quicker and sometimes I'll even have to walk for a bit to let the HR settle down a bit.  It's training not a race!

140 to 177 is quite a lot to be attributed to just 'drift'.  When do you have that 140?  If we're talking 140 after 1/2 mile or so, then probably your HR has not actually gotten up to reflect your effort at that point. 

It looks like your long runs are 7-9 miles or so right now.  If your HR at mile 3 or 4 is 140, and by mile 7 its 177, then that's quite a bit of change to be attributing to just drift.

Are you staying hydrated?  Is the temperature changing a lot during your run?  How's your nutrition?  Is your run significantly harder (e.g., hillier) coming back than going out?

Drift happens over hours of running, not just a few miles.

Sounds like you were just pushing it more as you went on.  To me it begs the question: what's the point of training by a HR monitor if you aren't "listening" to it?

happens to me. starts out in 140's..and depending on fatigue level/heat etc.. can end pushing 160 plus. If I look at the graphs, always looks to 'drift'. Sometimes I know its elevating...other times I feel fine. 
After doing a lactate training test, I know don't rely so heavily on hr alone.
I do tend to drift higher over time but after the 5 mile mark, it typically will drop back down.  

It looks like your long runs are 7-9 miles or so right now. If your HR at mile 3 or 4 is 140, and by mile 7 its 177, then that's quite a bit of change to be attributing to just drift.

Are you staying hydrated? Is the temperature changing a lot during your run? How's your nutrition? Is your run significantly harder (e.g., hillier) coming back than going out?

Reply: So, yesterday my HR was 140 at mile one! Started at 8:30 in the morning slight hill, nothing major and about 79 degrees and humid. Mile 2 150 HR, mile 3 157 HR, mile 4 164 HR, mile 5 168 HR. This is at a 10:14 to 10:30 per mile pace.

Temp is not changing much at all during the run.
Nutrition is good, I guess, have an appt with a nutritionist on Wed b/c I want to train for my first Marathon.
Hydration - I drink at least my BW in oz of water, some gatorade. I have eliminated caffine, but that was only a few days ago.

Thanks for the help.

I'm in the same boat....my long runs are about 6-7 miles. By mile one I'm usually around 150...it slowly drifts up...at mile 6 I have a hard time keeping it under 175...same effort about 10:30 pace. I can only relate it to heat, when I do treadmil runs in A/C at a slightly faster pace my hr is about 10 beats lower. From what I have read its normal...start in zone1 and end in zone 3 on long runs..