Just got the new 350/330 HO crate engine in my 29 RPU and running and now have a thermostat problem I've never encountered. When the car is cold (first start of the day or after total cool down), the temp gauge goes to 250 and stays there a short while before the thermostat opens, and then it slowly oscillates between 225-250 and 185 where it belongs. A little more info... Pulled out the old 305 which had no heat problems, even used the thermostat from that engine. When the first startup did the overheat, got a new thermostat and tested both in boiling water with thermometer and both were working fine. New thermostat goes in and same problem. All help/suggestions appreciated. Paul
If it fluctuates rapidly or when you rev the engine and especially from 225-250 to 185 deg. it is probably do to air pockets. You could try jacking the front of the car up when filling the radiator but it could also be caused by a porous head or bad head gasket letting air into the cooling system. Also make sure the lower radiator hose isn't collapsing and restricting flow.
What type of Gauge a Mechanical or Electrical?? Is the Radiator Cleaned & are you using a Shroud?? Electric Fan or Regular??
Make sure you have the correct intake gasket that matches the head and intake.I ***ume you are not using the intake that came with the crate motor.Give more info as to are you using any of the old parts such as intake,water pump etc.so others can give you correct info back.
I go with the reverse rotation water pump made mention of earlier that those H.O. engines come equipped with. Been there and done that once before.
Had a similar problem when the jack heads at Jiffy Lube flushed my radiator and didn't fill it all the way. Perhaps you have some high spots in the system that are trapping air?
The Jalopy Journal
