390 air pocket?

[paul cass]

hey guys
i have a 65 390 that i've rebuilt. after bout 10 minutes during the break in the engine temp was around 190 when i noticed water dripping out of the radiator cap. i shut the engine off and water burped out the overflow. i waited for the engine to cool down, added water and tried agian. same thing. i'm going to replace the radiator cap and check the timing. i've been told that 352's, 390's, 427's have a habit of trapping air in the back of the engine, i think in the heads. i'm a small block guy so working with big blocks is new for me. my idea is to raise the front of the car and take the plug out of the heater hose outlet in the intake and see if i can bleed off the air. it works on small blocks. any suggestions would be greatly appreciated.
thanks,
paul

[GEORGE ANDERSON]

Your idea will work or you can also drill a single or two or three small holes in the outside diameter face of the thermostat to allow the air to get out of the manifold.

[Michael C Henry]

Are you shure the thermostat bypass is open.That short peice of hose between the manifold and coolant pump. Kinked ,layers seperated , even a blister inside the short hose pinching off any flow.
Then there is the head gaskets the coolant passage is blocked at one end ,usualy the front. Coolant goes in the front of the block ,is pushed rearward around the cylinders. up into the head at rear and then forward through the head then into the water channel in the intake manifold and to the thermostat. If the head gasket was on wrong coolant wouldn't circulate in the rear .Coolant would go in the front of the block and up to the head and out through the manifold, a short loop.Any coolant and air in the rear of the engine would stay in rear.

[Tim Brewer]

Paul, if you're breaking your engine in, 190 degrees is no big deal. You should always expect higher temps when breaking in a new engine, possibly around 220 or so. As far as the cap, it could be just a bad one. If your engine is all new, 20 minutes @ 2000 RPM to break in the cam properly.
My .02, Tim

[Michael C Henry]

The temp sending unit is in the front of the intake manifold.If the whole system isn"t circulating emagine what tempreatures that the rear cylinders and heads are seeing are quite higher.. Once it boils cooling abilities fall off sharply. Vapor doesn't conduct heat as well as fluid . Since it is a fresh rebuild I'd bet that one or both head gaskets were on wrong.Just drill the old thermostat as George suggested or buy a new upscale thermostat that has air bleeds.Buy or barrow an infrared thermometer. You just point it at the surface being checked, pull yhe trigger, and it gives the tempreture of that surface. from as farr as 8ft. you don't get burned or dirty.I'd bet there is a big difference between the front of head and the rear.The coolant tempreature should gradually increase as it flows in the block rearward past each cylinder and then back forwards past each cumbustion chamberin the heads . The termometers run from $50 to $200. Craftsman has a dandy in their new 2004 holiday gift catalog for $149.99 . Laser indicater , pistol grip , back lit LCD and everything, it measures temps from -58° up to 1500° and they have another thermometer that reads temps from -58° to 1000° for $99.99 . You can use it to find dead cylinders by the exhaust temps.Bad spots in the radiater.bad bearings, low air pressure or out of alignment tires, hung up brakes,Anything where temp differences would be an indicater.
Almost every thermostat manufacture makes several grades of thermostats cheap to grand The better ones have the air bleeds allready incorperated into them ,are made from better materials , and are made so if they fail they fail in the open position. I know someone is buying the el cheapos but it isn't me.

[paul cass]

hey guys
thanks for all the info. i drilled a bypass hole in the thermostat. i've jacked up the front end and have added water and will let it sit overnight and see what happens tomorrow. i removed the plug in the heater hole outlet in the intake until water ran out. i'll try to find or buy a heat gun and try again tomorrow. the head gaskets were installed per instructions. i'll post the results of the next run of engine. thanks again everyone.
paul

[paul cass]

hey guys
after two days of frustration trying to figure out what is causing my engine to burp out water i think i may have found the problem. still having problems today i was ready to drive the car off the harbor bridge when a friend dropped in and suggested i check for a vacuum leak. i'd checked all of the hoses and found nothing lose and there was no noise or miss in the engine at idle. squirted carb cleaner around the base of the carb and found a huge leak at the back of the carb. turns out that the special order gasket from hi-lo left about an 1/8 inch gap at the back of the carb. gonna replace it with the CORRECT gasket tomorrow and see what happens. there was a tremendous gain in rpm when i sprayed the cleaner around the base of the carb. if this solves my problem, then i guess i won't have to take a dive off of the bridge. i'll report in later.
paul

[Michael C Henry]

I can't see how that would affect the cooling system. I'd bet your not done yet .

[paul cass]

hey guys
only had time yesterday to do a quick check. ran the engine for over 5 minutes with no problems. found that the timing was so for advanced i couldn't find it on the balancer. funny how a vacuum leak would affect the timing that much. reset the timing and now the engine not only didn't burp coolant it also ran cooler. anyway, i won't have a chance to check things more thourghly until thursday. keeping my fingers crossed.
paul

[paul cass]

hey mike
i have a question for you that it would be easier to answer if i could talk to you. would you mind sending me a phone number to my email fia28950@aol.com. if its ok let me know a convenient time to call.
thanks,
paul