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Old 12-30-2011, 05:32 PM
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Cooling and aluminum heads?

I've got a 496 642hp at the flywheel. I installed an aluminum radiator along with 2 14" puller fans. My thermostat is 180 degrees, but I have my fan set to come on at 190 degrees. Before installing this set up the car would run 190 cruising, but 220 and up sitting in traffic. That was with my 396 in it. Now with the new motor and new fan set up it's the opposite. Once it's warmed up and I start out it climbs to 190 the fans kick on it drops to 180. As I continue at a steady cruise speed around 2,500 rpm the temp slowly creeps up to 200 sometimes 210, but once I stop at a light. It drops back down only goes up while cruising. This is actually my first time with a set of aluminum heads! What is the max temp for an aluminum head, so I know were to keep the temp at? Right now its in the 60's to 70's during the day. when summer hit's it's 100+, so I'm sure my cruising temp will climb. I just want to know the limits. Just trying to get this cooling system right.Thanks!

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Old 12-31-2011, 05:53 AM
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alum heads

I have a p/u with 383 sbc with alum heads n a 67 Camaro 496 with alum heads.
On both the fans come on as soon as I turn the ign on, n they always stay on
I like to see at least 190 temp no more than 210 max both have the biggest alum radiators I could get in there.
I know what u mean about ambient temp,I live in coastal Alabama n it gets very hot here too
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Old 12-31-2011, 06:57 AM
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Do you have room for an OEM clutch fan? Those cool better than anything. If you can find one off a late 60's Caddy, they were about 19-20" & they move a lot of air.
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Old 12-31-2011, 10:30 AM
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Quote:
Originally Posted by tjet
Do you have room for an OEM clutch fan? Those cool better than anything. If you can find one off a late 60's Caddy, they were about 19-20" & they move a lot of air.
I'm not sure that I do I'll have to take some measurements. My fans are only about 3 to 4"'s away from my pully (pretty close). I do need to check into though. I do like the way it looks without the fan there, but I would like toget the cooling straight.
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Old 12-31-2011, 10:33 AM
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Quote:
Originally Posted by topwrench
I have a p/u with 383 sbc with alum heads n a 67 Camaro 496 with alum heads.
On both the fans come on as soon as I turn the ign on, n they always stay on
I like to see at least 190 temp no more than 210 max both have the biggest alum radiators I could get in there.
I know what u mean about ambient temp,I live in coastal Alabama n it gets very hot here too
Your actually not to far away! These temps around here sure can be extreme during the summer, and that's when you want to take it for a cruise.
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Old 12-31-2011, 02:10 PM
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Your fans could actually be limiting airflow at cruise. Did you change anything else.
What is your timing set at. Retarded timing can cause what you are talking about as well.

210 is not really in the danger zone. Does it top out at 210 or does it keep climbing.
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Old 12-31-2011, 04:01 PM
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Quote:
Originally Posted by T-bucket23
Your fans could actually be limiting airflow at cruise. Did you change anything else.
What is your timing set at. Retarded timing can cause what you are talking about as well.

210 is not really in the danger zone. Does it top out at 210 or does it keep climbing.
What I have is the aluminum 3 row rad with 2x 14" fans with a custom shroud that puts the fans about 1" away from the rad. When it finally climbs to 210 it pretty much stays there until I stop at a light then it will drop again. I never really drove it very long after it reached 210. If I had to guess I think it would max out at 215, but no more than that. I'm just worried about summer time cruising. I adjusted the timing according to my plugs I've got it set right in the apex of the grounding strap about 37 degrees. That was my first thought was timing, but the plugs read good after getting everything straight. It's really slow about climbing in degrees, but I just want to make sure if I take it on a little journey I won't have to pull over for cool down time.
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Old 01-01-2012, 09:37 AM
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T bucket is right in saying the best set up is a factory clutch fan (out of a diesel truck is best) and a big radiator is not such a bad idea either.
Sometimes its better to stick with what youve got.
the statament that your fans could be blocking the air is also right
I didnt remember where your fans are mounted front or rear of rad.
Did u drill a bleed hole in the thermostat?
Max timing I run in my big block is 38 all in by 2800 running 15 initial n the rest mechanical (no vacumm)
If your fans are cooling the engine when you are stopped it tells me you have a problem either with the fans actually blocking the air at cruise or an air flow problem under the car at speed(I.e. air blowing backwards from increased air pressure under chassis)
For air flow I check with water manometer behind radiator and also in engine compartment and in front of radiator in order to get delta p across radiator at different speeds,if you dont live too far from me I have the equipment to do this, n ill be glad to help you out,no charge.
Ive already got all the work I can stand building motors
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Old 01-01-2012, 11:45 AM
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Quote:
Originally Posted by topwrench
T bucket is right in saying the best set up is a factory clutch fan (out of a diesel truck is best) and a big radiator is not such a bad idea either.
Sometimes its better to stick with what youve got.
the statament that your fans could be blocking the air is also right
I didnt remember where your fans are mounted front or rear of rad.
Did u drill a bleed hole in the thermostat?
Max timing I run in my big block is 38 all in by 2800 running 15 initial n the rest mechanical (no vacumm)
If your fans are cooling the engine when you are stopped it tells me you have a problem either with the fans actually blocking the air at cruise or an air flow problem under the car at speed(I.e. air blowing backwards from increased air pressure under chassis)
For air flow I check with water manometer behind radiator and also in engine compartment and in front of radiator in order to get delta p across radiator at different speeds,if you dont live too far from me I have the equipment to do this, n ill be glad to help you out,no charge.
Ive already got all the work I can stand building motors
The fans are located in the rear of the radiator. I do believe the air flow under the hood is effecting it. Thanks for the offer. I'll try a few different things as far as the a clutch fan and a few others. If nothing corrects it I may get up with you and check the air flow. Thanks.
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Old 01-01-2012, 12:21 PM
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Heating at road speed is indicative of insufficient flow through the radiator. You just have to find the restriction. Before I would do anything else, I'd make a couple of 1" or 1 1/2" wood spacers to put between the hood hinge and the hood, so that the hood sits up higher in the back and allows underhood air to escape. It's nearly free and converts back to stock simply and easily, so why not try it?
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Old 01-01-2012, 12:23 PM
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Continue to do your troubleshooting of the cooling system, but also make another check.

I assume you are running a carburetor. However, I would recommend installing an O2 sensor and AFR gauge so that you can measure the AFR at cruising speed. You made a big jump in power and you may be undercarbureted and running lean at cruise. It may not be off by much (since the temp climbs slowly), but running lean will make the engine run hot. It goes back to normal at idle since the mixture usually runs fairly rich (12-14 AFR) to get a smooth idle.

Bruce
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Old 01-01-2012, 03:42 PM
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An easy way to check high under chassis tem is to do what tech inspector said.
This will relieve under hood pressure
Dont go messing around with clutch fans until u find whats wrong.
A lean condition on a holley carb usually will make the motor stumble(flat spot in carb) at about 5 to 7 in. hg.
If ur plugs look gud dont mess with jetting.
I really believe u have high pressure under chassis!!
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Old 01-01-2012, 09:00 PM
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You didn't say what kind of car this is. All stock cars have some kind of baffling to force air to go into the radiator and prevent under hood air from coming over the top of the rad or around the sides and going back thru it. Many cars have a spoiler under the rad to prevent air from going forward and under the rad. It also aids in providing a slightly lower pressure behind the rad causing the air to naturally flow thru it. If you have removed this it needs to be replaced or correctly modified to fit.
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Old 01-01-2012, 09:16 PM
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Quote:
Originally Posted by bentwings
You didn't say what kind of car this is. All stock cars have some kind of baffling to force air to go into the radiator and prevent under hood air from coming over the top of the rad or around the sides and going back thru it. Many cars have a spoiler under the rad to prevent air from going forward and under the rad. It also aids in providing a slightly lower pressure behind the rad causing the air to naturally flow thru it. If you have removed this it needs to be replaced or correctly modified to fit.
It's a 69 chevelle. The only thing I did was change the radiator and went with electric fans due to possible clearance issue's.
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Old 01-01-2012, 09:19 PM
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Quote:
Originally Posted by techinspector1
Heating at road speed is indicative of insufficient flow through the radiator. You just have to find the restriction. Before I would do anything else, I'd make a couple of 1" or 1 1/2" wood spacers to put between the hood hinge and the hood, so that the hood sits up higher in the back and allows underhood air to escape. It's nearly free and converts back to stock simply and easily, so why not try it?
I was actually trying to think of a way to release underhood air to see if it would help. Thanks for the advice. I'll try it out and see what happens.
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