I have a 91 GT with a 347, aluminum GT40 heads, Trick Flow intake, 4 core Northern aluminum radiator, dual black magic fans, 180* thermostat, stock water pump. The car runs fine and stays right at 180* unless I romp on it a few times, then it starts to overheat. Someone told me the stock water pump might not be flowing enough for the big aluminum radiator, could this be the case. Someone also told me I have a blown head gasket, if that were true wouldn't it be overheating just sitting and idleing, or under normal driving conditions? Any help anyone can give me on this would be great thanks.
Overheating 347, any help appreciated
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It could possibly be your electric fan is too weak for the 347. I run a pep boys 3 core radiator, autozone stock replacement pump, 180* mr gasket thermostat and a sn95 electric fan and it cools my 11:1 347 just fine.
A blown head gasket won't make the car over heat necessarily.
A blown head gasket won't make the car over heat necessarily.
Juiced88Coupe
Founding Member
OEM fan set-up hurts horsepower, if that is what you are after.
A Black Magic fan does not take up enough radiator area in my opinion to effectively draw heat out of it.
As for the overheating, sounds like a lack of flow or capacity is the issue.
I used to have a very similar issue, but mine was solved when I added a h/c/i package.
New radiator and new headgaskets were a part of that.
A Black Magic fan does not take up enough radiator area in my opinion to effectively draw heat out of it.
As for the overheating, sounds like a lack of flow or capacity is the issue.
I used to have a very similar issue, but mine was solved when I added a h/c/i package.
New radiator and new headgaskets were a part of that.
Juiced88Coupe
Founding Member
I should have been more clear I guess, use a OEM electric fan, Taurus, MK VIII, ect.
PUNISHER RACING
Active Member
I know this might sound stupid but is the water pump turning the right way, CCW I only say this because I have seen it happen!
PUNISHER RACING
Active Member
Sounds like you are pushing water through the rad too fast, maybe try a smaller crank pulley. Did you ever have a LM1 on the car before you might be real lean also. Its not the old flipped head gasket issue is it?
You cant push water through the coil too quickly - it's a closed system with impediments that restrict flow naturally.
As David mentioned, you very well might not have enough heat rejection ability. The radiator does ok at idle and cruise but when you get on it, it cannot reject the additional heat-per-time that's created.
The last quick variable is to ensure that the air dam is present (if you doubt your fan, to have a valid test, you have to romp on it and then keep cruising at 50 mph to see if temps come back down. There needs to be air flow through the coil and the air dam is very important in this regard).
As David mentioned, you very well might not have enough heat rejection ability. The radiator does ok at idle and cruise but when you get on it, it cannot reject the additional heat-per-time that's created.
The last quick variable is to ensure that the air dam is present (if you doubt your fan, to have a valid test, you have to romp on it and then keep cruising at 50 mph to see if temps come back down. There needs to be air flow through the coil and the air dam is very important in this regard).
True Hisson but like any part if it is old perhaps it has broken somehow. i know its not common but its always those things that seem to bite me in the butt.
The upper hose was real firm when the thermostat should of been open, I was at a red light light last night and it shot up to 240*, I pulled over let it cool down, took it to a buddies shop. We pulled out the thermostat and now its running fine, very cool with no thermostat but it was also 25* here last night. I think I will slap a Mr gasket 160* thermostat in it and let it ride. Maybe the old 180* was just stuck? No signs of oil in the coolant or vice versa though so I guess thats a good sign.
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