Overheating Big Block HELP PLEASE !!!! - Team Camaro Tech
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post #1 of 24 (permalink) Old Sep 4th, 07, 05:54 PM Thread Starter
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Angry Overheating Big Block HELP PLEASE !!!!

Ok I will try to give all details so that someone out there will be able to see what I am missing.
The subject is a 68 Camaro with a 71 402 Big Block .030 over. very mild engine.

Car ran great. Had a small block radiator with no shroud but ran 180 in traffic no issues. It went through a mild "restoration" where the roof was replaced and car was painted. I added Vintage air along with a factory replacement new big block radiator with shroud. It now runs hot. 190...then up and up to 220 and I believe it would go further but I have been able to get it out of traffic by that time. It runs hot with the air off, and with it on. It runs ok at speeds of 35 to 50 but the minute you stop it starts to go up. It also gets hot if you are running 70 or above.

Here is what I have done.
New theromstat
2nd new theromstat this time 160 deg
New 600.00 alum radiator ( This one is much bigger that the Big Block and 3 tyimes the size of the small block one)
new temg gage ..just to see if it was reading wrong
Tested by cranking engine with radiator cap off to see when thermostst opened up and if water was flowing. You can see the flow in the radiator.
New radiator cap
New overflow tank

remember this is a car that ran cool with the wrong radiator and no shroud. It now runs hot even if I remove the belt from the AC. No chance to run AC unless you are driving the 35 to 50 speed with no stops.

I have added an electric pusher fan to the front side of the AC coil just as Vintage Air told me to do. I have made a air shield between the radiator and the core support so that all air must go through the radiator.

I am runnung a 18" 6 blade mechanical fan with no clutch because the long waterpump of the 71 model engine in a car that had a short pump will not allow for the clutch.

The fan is a high flow stainless unit.

As you can see I have spent many hours and dollars to get to this point. I am ready for your ideas and hope that someone here will see what it is that I have missed.

THANK YOU IN ADVANCE FOR ANY HELP. As you can tell, I have no more ideas. You can contact me direct at [email protected] or respond here.


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post #2 of 24 (permalink) Old Sep 4th, 07, 06:26 PM
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Re: Overheating Big Block HELP PLEASE !!!!

wheres the fan sitting in to relation of shroud.also in order to replace heater box needed to remove passenger side fender correct?or inner wheelhouse. when they put it back together did they put seam sealer from cowl to fender. that will not allow air to flow out of engine compartment.when you did a/c conversion did you put your temp sensor in different spot also.did you take out by pass hose also. just some thoughts for you. what happened after the conversion you did.
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post #3 of 24 (permalink) Old Sep 4th, 07, 06:50 PM Thread Starter
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Re: Overheating Big Block HELP PLEASE !!!!

Great questions..Thanks

The fan sits about 1" from the radiator and the blades are about 1/2 way in the shroud. The fenders were both off for the body work and the factory heater box was removed. There was no seam sealer added in the fender area. The Vintage air plate is sealed to the firewall per the instructions. The temp sensor goes into the drivers side head. I have since removed it and installed it in the intake. I even had 2 temp gages in at one time to see if that was an issue and the temp from the head or the intake was the same. The car had 2 bypass hoses on it and I did remove one so that I could install the heater hoses. The heater works and blows hot air and the bypass hose that is still there is the one that is closest to the drivers side.

Thanks for the help. If you see anything here that I need to check, please tell me. I do not pretend to be a mechanic, only a hobbiest. THANKS Mark


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post #4 of 24 (permalink) Old Sep 4th, 07, 07:15 PM
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Re: Overheating Big Block HELP PLEASE !!!!

you just about threw all my sugestions out the wall. 1 last thing where does that by pass hose goes to. i cant help on that since i dont have a big block.but pictures may help. i know people with big block 68 and 69 cars.i took over a 1000 pictures while redoing my 67. some help others and alot dont.theres soo much to a car that you can amagine.
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post #5 of 24 (permalink) Old Sep 4th, 07, 07:22 PM
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Re: Overheating Big Block HELP PLEASE !!!!

Is this the same fan you were running before?





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post #6 of 24 (permalink) Old Sep 4th, 07, 07:30 PM
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Re: Overheating Big Block HELP PLEASE !!!!

As thorough as you are, I bet you've already checked this...
Any chance the distributor got moved while all the work was going on? Retarded timing will get them hot.

Did all your pulley sizes for the water pump and fan stay the same when you added AC?

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post #7 of 24 (permalink) Old Sep 4th, 07, 07:48 PM Thread Starter
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Re: Overheating Big Block HELP PLEASE !!!!

Guys thanks...The bypass hose is in the righ place for sure. The pulleys did not change during this deal and I have changed the timing 10 times trying to see if any changes are made. Keep thinking guys, my brain hurts and I am out of ideas. If I had the cash I think I would buy a small block to go in there...............Oh no what am I saying? ha ha

THANKS MARK


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post #8 of 24 (permalink) Old Sep 4th, 07, 08:12 PM
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Re: Overheating Big Block HELP PLEASE !!!!

I can only come up with one way to troubleshoot it without buying electric fans plural. And that is to remove the condenser and test drive it. I hope somebody with a better idea comes along.

I'm not into car fans and I know there's lots of flavors available. I think JimM was headed somewhere with his question.

My junk we just increase the blade pitch or increase the quantity of blades or speed them up to fit the job. Keep the fan tip speed at around 13,000 FPM. Next week I kick off a job where I am throwing away a 20,000# cooler with an 11' fan and putting a bigger cooler with either a 12 or 13' fan I forgot.


You didn't bolt your fan on backwards by any chance?

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post #9 of 24 (permalink) Old Sep 4th, 07, 08:12 PM
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Re: Overheating Big Block HELP PLEASE !!!!

Quote:
Originally Posted by JimM View Post
Is this the same fan you were running before?
?





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post #10 of 24 (permalink) Old Sep 5th, 07, 03:40 AM Thread Starter
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Re: Overheating Big Block HELP PLEASE !!!!

Same fan as before and it is bolted on the right way. The bypass hose is there also.

I hate to remove the ac condensor for a test because that means recharging it after and as was said there are plenty of BB with AC so this should work. Even Vintage Air has run out of ideas for me????
Mark


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post #11 of 24 (permalink) Old Sep 5th, 07, 04:12 AM
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Re: Overheating Big Block HELP PLEASE !!!!

You've added a top plate between the header and core support, good. Did you add one from the bottom valance and core support? Heavy poster board and duct tape would be a good science project just to see. Anything you can do to prevent/cut down recirculating hot air.

No need in pulling the AC condensor. Higher pressure rad cap?

I believe the fan, 6-blade 18 in dia is good, but, it is driven faster than crankshaft rpm, by 30%? If w/pump pulley is 6 inch, you need a 7.5 or 8 inch crank pulley.

High flow thermostat? MRG-4364? A Stewart water pump maybe next.

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post #12 of 24 (permalink) Old Sep 5th, 07, 04:34 AM
 
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Re: Overheating Big Block HELP PLEASE !!!!

Hi, A couple of thoughts. You have to be careful as to the mixture of antifreeze and water . If you have more than a 50/50 mix of antifreeze you can have an overheating problem. Antifreeze doesn't absorb heat from the engine as well as water. The greater the concentration of antifreeze beyond 50/50 the greater the overheating. Also a radiator hose that has to sharp a bend can cause a problem as can a hose that is soft and closes at speed. Lew
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post #13 of 24 (permalink) Old Sep 5th, 07, 06:07 AM
 
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Re: Overheating Big Block HELP PLEASE !!!!

You could possibly have an air pocket somewhere in the engine. Have you burped the system?
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post #14 of 24 (permalink) Old Sep 5th, 07, 06:34 AM
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Re: Overheating Big Block HELP PLEASE !!!!

The "runs hot below 35 mph" clearly indicates that for whatever reason, the fan is not pulling enough air thru the core.

Try one of these: http://store.summitracing.com/partde...5&autoview=sku for forty bucks, what have you got to lose?

No comment on "over 70" as I have no info on gearing...





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post #15 of 24 (permalink) Old Sep 5th, 07, 06:53 AM
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Re: Overheating Big Block HELP PLEASE !!!!

Quote:
Originally Posted by 502prostreet View Post
You could possibly have an air pocket somewhere in the engine. Have you burped the system?
That's what I have been thinking.

In addition, I have a question. You mentioned the distance from the radiator, and the distance the fan is inside the shroud.
What is the distance from the fan blade edges to the shroud?


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