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Hey guys, been on here before and had lots of help so I appreciate that and figured I’d ask the experts again, I have a continual overheating issue while at idle.
My set up is a 74 with all mix matched parts
It’s 80’s (I think) model 350 crate engine, stock as far as I know. I have a fairly basic yet new radiator that has a 17x21 core and I believe only 1 possibly 2 rows (had to keep it basic for cost). A 16 inch electric fan with a shroud. My mechanical sensor is located on the driver side head. The issue is my engine will steadily heat up straight to 220 without stopping.i always shut it off at 220. It takes around 15-20 minutes to do so while at idle. However if I rev it then the temp increases much faster. The car is driveable however not really road ready so I can’t test it to see if it would still overheat while moving with more airflow. So far I’ve increased the fan size as big as I can fit, heat taped the sensor exterior so that it won’t soak any heat from the headers. And taken out the stat completely. Possible issues I see is no bypass hose from pump to intake (was told this isn’t required but I’m curious now), and possibly need a larger radiator. So my questions for you guys are:
1. Do you think my issue is airflow since it isn’t moving?
2. Thoughts on the bypass hose for increased cooling?
3. Any parts or upgrade recommendations to keep it cool?

I read several threads on here and some said to move the temp sensor to the intake which would solve my problem temporarily however I feel like that would cause issues in the head or at a longer time idling. I thought about getting a better radiator but wanted to see if there were any other suggestions before I spent all that money on a nice one. Any ideas or input or criticism would be much appreciated, this is my first build and I’m trying to stumble through it. Thanks in advance guys
 

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overheating

Hey guys, been on here before and had lots of help so I appreciate that and figured I’d ask the experts again, I have a continual overheating issue while at idle.
My set up is a 74 with all mix matched parts
It’s 80’s (I think) model 350 crate engine, stock as far as I know. I have a fairly basic yet new radiator that has a 17x21 core and I believe only 1 possibly 2 rows (had to keep it basic for cost). A 16 inch electric fan with a shroud. My mechanical sensor is located on the driver side head. The issue is my engine will steadily heat up straight to 220 without stopping.i always shut it off at 220. It takes around 15-20 minutes to do so while at idle. However if I rev it then the temp increases much faster. The car is driveable however not really road ready so I can’t test it to see if it would still overheat while moving with more airflow. So far I’ve increased the fan size as big as I can fit, heat taped the sensor exterior so that it won’t soak any heat from the headers. And taken out the stat completely. Possible issues I see is no bypass hose from pump to intake (was told this isn’t required but I’m curious now), and possibly need a larger radiator. So my questions for you guys are:
1. Do you think my issue is airflow since it isn’t moving?
2. Thoughts on the bypass hose for increased cooling?
3. Any parts or upgrade recommendations to keep it cool?

I read several threads on here and some said to move the temp sensor to the intake which would solve my problem temporarily however I feel like that would cause issues in the head or at a longer time idling. I thought about getting a better radiator but wanted to see if there were any other suggestions before I spent all that money on a nice one. Any ideas or input or criticism would be much appreciated, this is my first build and I’m trying to stumble through it. Thanks in advance guys
You say mixed parts on an 80s crate motor---here's some things i've run across ---all cause the heatup you describe.
#1--thermostat installed upside down by customer
#2--wrong intake gaskets--80s tbi motors had blockoffs made into the gaskets on one end---these are supposed to be in the rear of the engine---if you flip them to the front the temp. will go straight through the roof.
#3--Has the intake been off ? You can check the intake gasket install stated above by removing the thermo & run a coat hanger down the inside to the head coolant port.
#4--bad clutch fan---freewheels constantly---no lockup.
#5---put a 180* thermo in it---Also seen jammed thermostat spring & pellet.:)
 

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Discussion Starter #3
Thanks chevydealer35 for the advice. I currently don’t even have a thermostat in it to try and see if that was the issue but it overheats regardless of the thermostat. And I replaced the mechanical fan with an electric fan so that should have fixed that issue. However the intake is an edelbrock performer intake on it that was on the engine when I got it. Unless that was an option on crate engines that I’m not aware of I guess that would mean that it had been removed and replaced so it’s possible for the gasket to have been installed wrong like you mentioned. I will have to check that today after work. I did not know that was even a possible issue, thanks so much I’ll check and update you!
 

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1967 Chevy II nova Hardtop
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First, Install a 180' thermostat. No fan produces more volume than a mechanical fan. A large fan with clutch and shroud with blades half in and half out will maximize your cooling system. Lastly get it out on the highway. If it overheats at cruising speed either the radiator is too small for the engine or the engine is not tuned properly.
 

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Make sure your timing isn't retarded. Retarded timing dumps a lot of heat into the exhaust and gradually heat-soaks that head-mounted temp sander. A lean mixture is also a tuning-related possibility.
It's harder to diagnose airflow and cooling capacity issues sitting in the garage.
 

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Any chance the water pump is for a serpentine setup, it may be running backwards?
 

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Discussion Starter #7
Well I’m back with an update,
I finally found the issue however it wasn’t exactly anything mentioned above. Although without those suggestions I’m not sure I would have found it. I found some time to work on it today and was going to start down the list of suggestions and start with the easiest to check and work my up to the harder/more expensive stuff. Well first thing I checked was if my water pump was turning the correct way. I disconnected the upper hose at the radiator and started turning the pump by hand to see if it sucked or pushed. Well it wasn’t doing either which I found weird since it’s a brand new water pump. Just as I was about to tear into it I thought I saw something inside the upper hose and sure enough, somehow a decent sized chunk of rubber had gotten inside it and was lodged and blocking the coolant. Not sure what it was or how it got there, I’m guessing scrap from the store or making it and it just got stuck somehow, but either way I removed it and sure enough it runs just as cool as can be now, crazy how it’s always the smallest thing wrong when you can’t figure it out. However I wouldn’t have found it without looking into y’all’s suggestions so I truly appreciate the help, the suggestions have just taught me what to look for next time I’m dealing with a car with this issue, so thanks again everyone I appreciate it!
 
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