Is this temp ok?

I currently have three plants growing in a 3'x3'x6.5' area. My light is a 400w hps on a lumatek ballast. I have a air cooled reflector attached to a 170cfm inline fan with a carbon filter, with the air being exhausted outside. I have an open port for intake but no intake fan. The temperature in the room with the light on and the fan on full speed is usually from 84 to 87 degrees. This is my first grow, and most of the information i can find says to keep the temp around 75. The plants dont seem to be unhealthy at all, but i would appreciate some feedback on whether or not this is an acceptable environment for my ladies. Also, if this is too high, how do i lower the temp if an ac unit isnt an option? Any help would be greatly appreciated.

You'll find your temperatures will probably rise as your plant grows and airflow is restricted. My room is around 30C most of the time and I don't have too many problems. Just keep at it and look for signs of heat stress (if you don't know them, read up on it). As soon as you see it you need to increase the airflow. I have three 65CFM fans mounted inside 120mm ventilation pipes - one for intake, one for exhaust and one for just blowing air around.. Seems to work quite well, and I can put two on the exhaust if necessary. A single small desk fan to blow gently across your plants would probably help you.

I suspect that you are asking too much of that 4 inch fan. I'm guessing that this isn't what you want to hear but, I think that another fan may be in order. If you run one on the filter and the other on the lamp I suspect that you will get back into a better range on the temps. You could get a larger fan and use the current set up as well but, then you may be looking at fitment issues on the filter and hood flange. Good luck with whatever land on.