400 Problems continue with heads?
Thread Starter
Pro
Joined: Nov 2009
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From: Maple Grove Minnesota
400 Problems continue with heads?
Casting 997 the temp sending unit which doesn’t seem to be working is located in the rear of the passenger head which is going to be a PITA to change if I need to.
There is another ½” npt threaded hole in the drivers side head between #1 & #2 cylinders. The hole is larger then the temp sending unit from the L98 so I used a reducer and the gage started working but it went up to 299 in a matter of a half mile.
The engine was not overheating and running fine, I stopped and checked under the hood and a few minutes latter the fan cam on. Shouldn’t there be coolant flowing where this hole is? When I pulled a plug to put the temp sending unit it was dry?
There is another ½” npt threaded hole in the drivers side head between #1 & #2 cylinders. The hole is larger then the temp sending unit from the L98 so I used a reducer and the gage started working but it went up to 299 in a matter of a half mile.
The engine was not overheating and running fine, I stopped and checked under the hood and a few minutes latter the fan cam on. Shouldn’t there be coolant flowing where this hole is? When I pulled a plug to put the temp sending unit it was dry?
Le Mans Master
Joined: Aug 2010
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I may be wrong, but, if I remember right , those heads are "kinda" rare. you might do some research. probly sell em and get 'nough dineros to buy all kinds of new parts for your car. Whatever you do dont do any custom work to them before you do the research. my bad , I was thinkin early vett heads , very sorry
Last edited by oldalaskaman; May 22, 2011 at 07:44 PM.
Race Director
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From: moraga ca
You should have lose a good amount of coolant when the sensor was removed and replaced with the reducer and the sensor replaced.
Thread Starter
Pro
Joined: Nov 2009
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From: Maple Grove Minnesota
I’ll have to bring it up to temp so the thermostat opens and remove the sensor from the left head to see if I get any coolant. I don’t think it is flowing through the head with temps high at 299 which must be as high as the gage goes?. Where would a blockage be if there is one and how can I fix it or can’t I?
Drifting
Joined: Oct 2006
Posts: 1,328
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From: Stafford Connecticut
If you used felpro 400 gaskets and you purge your motor of air there is no way you would not be getting water to the heads.Like it was stated above you should get major water out of the heads when you pull the sensor.Do you have the steam holes drilled in your heads?
Le Mans Master
Joined: Aug 2010
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dont 997/400 heads come with steam holes already drilled? when we used to run 350 heads on a 400 we used the 400 gasket as a template for the holes. wonder if he's using 350 gaskets? did some research , 997 was used both on early and late small blocks, strange. Those 997 400's are worth bout double some of the other 400s due to thicker wall casting, but not near as much as the 57 corvette heads....trivea.
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Le Mans Master
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I like this, respectfully, bob
Thread Starter
Pro
Joined: Nov 2009
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From: Maple Grove Minnesota
Problem solved, took the thermostat out then removed the radiator cap and all the coolant drained into the engine. Added coolant, started up and brought up to temp, stat opened, fan came on at 228 and off at 215 
Drifting
Joined: Oct 2006
Posts: 1,328
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From: Stafford Connecticut
That's a round about way of purging the cooling system.I am glad you got it fixed.
On a side note if your motor starts to get to hot again you might consider changing your thermostat it could be sticking closed.
On a side note if your motor starts to get to hot again you might consider changing your thermostat it could be sticking closed.
Race Director
Joined: Apr 2003
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From: moraga ca
Glad it worked out. When I'm filling the coolant on a new motor, I fill the intake manifold first, put the thermostat in, button up the thermostat housing and then fill up the radiator. This way I know the block and heads are filled. Good luck.
Thread Starter
Pro
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From: Maple Grove Minnesota
Thanks, IF I do this again (lol) you can bet I’ll do the same thing. Thank the God the engine doesn’t show any sign of damage from the amount of time I ran it not knowing it didn't have water in the heads.
This thing has got tork up the ying yang and if I’m not careful it’s going to get me in trouble. But damn is fun! I haven’t had a hot rod for a long time.
There is a car show locally coming up on the 28th that I may take it to. For $60 you can enter the Dyno Challenge to see just what it has? I should really have it tuned first but no time.
This thing has got tork up the ying yang and if I’m not careful it’s going to get me in trouble. But damn is fun! I haven’t had a hot rod for a long time.
There is a car show locally coming up on the 28th that I may take it to. For $60 you can enter the Dyno Challenge to see just what it has? I should really have it tuned first but no time.
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Pro
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From: Maple Grove Minnesota
Now the coolant reservoir is boiling over though she was going to blow yesterday she really swelled up like a pumpkin. Is this air in the system that causes it to boil? If so how can I bleed it out? The car is not over heating but is running like crap. Put the scanner on it and code 13 came up o2 sensor and lean exhaust?
Thread Starter
Pro
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From: Maple Grove Minnesota
The stat is new but could be defective but the engine it self is not over heating? I picked up a new radiator cap and more antifreeze going to give that a try and see what happens.