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Old 10-15-2013, 12:26 PM
mprat mprat is offline
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Default Overheating Big Block

Now after finishing my 67 Chevelle, I took it for a test drive and it seems to have a overheating problem. It is a stroked 454 crate motor. Has aluminum heads, bored .060 has 10.5 forged pistons... I have a three core aluminum radiator, two electric fans, running a single belt march system with reverse flow water pump. tried 195 and 180 thermostat and nothing changed. When I took it down the highway and would reach 190 hang there a short time then up to 200 to 205+ I would get it back to the garage and it would blow water in the overflow and eventually on the floor. I tried it just sitting and at 190 it would start to flow water into the overflow tank which seems odd to me. It has a 16lb cap and I have tried two. The outside temp was 85 on several test runs. But the other day we had a front come through and at 75 I drove it and it stayed at 190, which I thought it should have ran cooler. the fans are working fine, I do not know how to proceed in what could be the problem. I have never ran a reverse flow pump. But we have run out of things to check... any ideas???
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Old 10-15-2013, 01:04 PM
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fleming23 fleming23 is offline
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It should definitely not be puking coolant at 190 degrees.

I would normally think you need a new cap but you mentioned trying two. Have you verified your temps with either an infrared gun or different temp gauge? You can pick up a cheap temp gauge at your local part store pretty cheap, or Summit has a variety of gauges you can order for not much $$.

Before anyone tries to convince you otherwise, you can absolutely cool a big block motor with electric fans. Many will want you to swap to mechanical clutch fans but that is traditional, I'd rather use points for ignition because it came that way 50 years ago, thought process. I look at that the same way I do those who say electric fuel pumps are no good on an old car. This too is bogus, but you can't just slap some cheap part on and expect it to work as well as something that was carefully engineered by a multitude of well-paid GM employees. You do need to CAREFULLY and thoughtfully plan out your cooling system while making sure to not skip any area. You need quality fans with good relays and wiring. These fans need to be mounted with some kind of shroud - this I suspect you lack. Many fans come built-in with a plastic shroud that mounts to the radiator and/or core support. They often have flaps to allow air to flow through at highway speed but close at idle so that you pull as much air across the radiator as possible. If you have two fans just quick-tied through the radiator and no shroud, you will very likely have problems.

Also, how do you have your fans programmed to turn on? Is there any type of relay/controller or is it simply a switch?

Again, I do not think at 190 degrees you should be seeing any coolant bypass the radiator cap. This still seems wrong to me as 190 is normal operating temperature, even 205 is not really overheating but is certainly warm (or warmer than I like to see my car get.)

Post some photos of your set up and maybe something will jump out.

When your fans come on, how hard do they blow? If you held a piece of paper either in front of the radiator (not as easy to do) or behind the fans, how hard does it pull/blow air?

EDIT - Why do you have a reverse flow pump? Is this a serpentine system?
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Last edited by fleming23; 10-15-2013 at 01:11 PM.
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Old 10-15-2013, 07:45 PM
mprat mprat is offline
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Yes it is a serpentine single belt. The water pump came in the kit. The fans are not flat against radiator. there is a flat aluminum plate that the fans mount to that holds them about 1/2in from the radiator. The fans are on thermostat control, and come on at 180deg, or when the air is on. the plate is solid there is no rubber flaps. I had those on my previous car but this one does not. The fans seem to move air across the radiator fine but nothing to brag about. I put in a new temp gauge to make sure it was correct. I might suspect it could be in the fans, being no flaps it would not allow good air flow going down the road. I sent a pic to check out and see what you think. I tried to spare no expense on my cooling system. The fans came as an assembly with the radiator....
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Old 10-16-2013, 07:18 AM
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fleming23 fleming23 is offline
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Well that set up is certainly better than what I had in my mind. The flaps can certainly play a role going down the road but the car should be able to maintain normal operating temperatures while idling. There was a thread on Team Chevelle by Brandon from ATK Engines with a similar looking shroud and he was having very similar issues with his electric fans. I only briefly paid attention to his issues but I do remember him taking a hole saw and making holes in his shroud so air could freely flow through the shroud at highway speed. I'm not sure that was his entire issue but when the shroud is solid like that it basically creates back pressure and does not allow the air to move across the radiator like it should. You would think it would just tunnel it through the fans but that is apparently not the case....

Is your issue isolated to while driving or can you sit at idle for an extended period without overheating? I'm still not sure about your overflow at 190 issue. The only logical thing there is the cap. I would definitely put either a 180 or 160 degree stat in the car with a bypass or a small hole drilled.

The temps are coming down so it makes troubleshooting these issues a bit more difficult as these cars will run cooler by default. Let me know if the car can idle without overheating. Also, how is the timing set? Do you have vacuum advanced and if so is it on full manifold vacuum or ported?
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Old 10-16-2013, 07:24 AM
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Hank70SS Hank70SS is offline
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Well I'll go in a different direction. What's your ignition timing set at, initial and full advance? Are you running a vacuum advance? Manifold or ported?


Oops! Missed Eric's last post, he already asked these questions.
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Last edited by Hank70SS; 10-16-2013 at 07:27 AM.
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  #6  
Old 10-16-2013, 09:10 AM
mestorod70 mestorod70 is offline
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First thing that jumps to mind is the reverse flow pump.
Have you re torqued your head bolts.
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  #7  
Old 10-16-2013, 02:04 PM
mprat mprat is offline
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Ok I have just finished running it for 25 minutes in the garage, paid close attention to the temp when it pushed fluid into the overflow tank. At 185 deg it filled fluid into the tank but less than half way, really weird why its doing that. The next thing it never got above about 185, but if you put your hand on the top part of the radiator it will fry your hand, and I have stainless water hoses, if you touch the top one same thing you cannot hold on to it. BUT I can reach down and grab the bottom hose and keep my hand on it with no problem seems less than half the temp of the top section... what the heck is going on. Right after I started it maybe less than three or four minutes I was just going to watch and see if the water was flowing after the thermostat opened up , it blew water everwhere like it was under severe pressure......... Im still going to check the timing, but I think if it sits and runs a good temp it should not be that....It is a vacuum advance, at the carb.timed at 10deg... the temp outside is at 70deg so I decided to go for another drive, temp climbed to 190, then in a few minutes it climbed to 205 so I decided to take er back before it got too hot... let it run in the garage with a big fan running in front of it to see if it would cool down, it would not, sucks I cannot even drive the car after all that work. It does have a 180 stat in it and there are a couple of holes drilled in it....

Last edited by mprat; 10-16-2013 at 08:47 PM.
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  #8  
Old 10-16-2013, 02:52 PM
Garyb Garyb is offline
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You should keep the cap off until the thermostat opens up and water starts flowing through the tubes. You might have a big air pocket in there.
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  #9  
Old 10-16-2013, 03:30 PM
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Stormer Stormer is offline
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I had some issues with my mild 350 too.
Two things solved it:
a) correct the timming advance;
b) change the cheap electric sensor for a good (AutoMeter) mecanical one.

Solved!

Of course the "b" alternative have nothing about really cooling the engine, but several people talked to me about bad temperature sensors.
Check it!!!
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Old 10-16-2013, 03:31 PM
mestorod70 mestorod70 is offline
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Do you have your old pump and V belt pulleys.???
Just a thought.
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