Heat problem

[Taylort]

No heat in 79 chevy k20

[bd]

...I have a heat issue......heat is nice and warm when the truck is just sitting and running but as soon as I start to drive it down the road all I get is ice cold air. With winter approaching its going to be a cold winter.

Make sure the vent doors are closing properly and the seals aren't shredded.  If the problem remains, verify the cooling system is full, make sure the proper thermostat is installed and functioning, and flush the heater core with a garden hose.

[Irish_Alley]

im with bd about thermostat. but its just a guess to you eliminate the other problems

[Taylort]

If it is the thermostat any ideas what thermostat I should be running on a 383 stroker?

[Irish_Alley]

still should be 185 if you want colder 165 but it almost sounds like you have no thermostat. the rating on the thermostat will still trip at that temp no matter what engine its behind. so i would go 185 but thats me

[78BIG-TEN]

Your choice 160,180,or 195,I'm pretty sure 195 was oem,it was in my 78 anyway

[Irish_Alley]

Yeah big ten is right. Been some years I messed with the thermostats

[bd]

As 78BIG-TEN posted, 195° was OE.  But, really, it depends on how the engine is dressed and the climate where you reside.  IMHO, for a crude guideline: lots of power adders and/or living in hot areas of the country use 180°, otherwise, 195°.