'89 2.3L Isuzu Pickup...Won't Start When Warm

[Tscape16]

So I think I found out what was wrong with my '89 Isuzu Four Cylinder. It will start up fine in the morning...but after I drive it for like 10 minutes, it will just turn over, and turn over without acctually starting if I turn it off and try to start it again. I'm getting gas, I just think I don't have enough air coming in. The air filter has been changed...everything is hooked up. On a website, a guy with an '89 Mazda 929 was having the same problems. My temperture gauge is not working right now...so if that isn't working...it will tend to retard the spark apparently when the engine gets warmed up right? Timing must get bumped up or down as the engine warms or something? Let me know if you think I'm on the right path to getting this thing fixed or if something else needs to be done.

*The head just got rebuilt...and before that it started just fine....I have been running it to work the last months because it will sit for 10 hours w/o moving so it will be cooled down by the time I have to leave. I'm just worried I will kill it and I won't be able to start it in busy city traffic! Thanks for the help!