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Unread 2014-06-30, 04:31 PM   #1
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Default BBC Nova overheating on the highway. Suggestions?

468 BBC with iron heads.
C&R racing 3 1" core rad
2 12" 1550cfm electrics set up to push (shroud won't fit). They are getting full amps.
Standard long BBC water pump
180* stat that seems to be working
Lower hose doesn't seem to be collapsing at speed, but it does bulge a bit when it's hot.

The car generally behaves it's self at regular road speed, but as soon as it gets on the highway, the temp jumps to 220+. It won't get quite as hot when the air temp is in the 70s, but at 80+ it really suffers.

I've always exited and shut it off before it starts to boil.

What do you guys think are my weak points?
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Unread 2014-06-30, 04:37 PM   #2
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Bigger radiator..

Edit: put a 427 in my cj7 a while back. Switched to electric fans like you did, used a 3 row radiator with the fenders off and it would still over heat. Switched to a 4 row and it worked just fine. Cost a bit more but it was worth it vs the headaches..
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Unread 2014-06-30, 04:42 PM   #3
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A couple of things:

While your fan being setup in push mode is far from ideal, it is a non-issues at speed.

As with almost all muscle car era cars, I am going to assume there is no form of baffling or and air dam to coax air to actually go though the radiator instead of around it.

An iron headed BBC is going to generate a TON of heat energy especially if timing is retarded via a lack of vacuum advance, and/or less than ideal base timing. I am going to ASSume this actually isn't a low compression small cam setup which will also produce excessive heat.

The grill opening on those cars isn't exactly big, so getting in cooler ambient air becomes a bit of a trick especially with the aerodynamics of those cars.

Headers? Are they coated or wrapped?

Take some pics of the area around your radiator.
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Unread 2014-06-30, 04:56 PM   #4
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Originally Posted by snm95ls View Post
A couple of things:

While your fan being setup in push mode is far from ideal, it is a non-issues at speed.

As with almost all muscle car era cars, I am going to assume there is no form of baffling or and air dam to coax air to actually go though the radiator instead of around it.

An iron headed BBC is going to generate a TON of heat energy especially if timing is retarded via a lack of vacuum advance, and/or less than ideal base timing. I am going to ASSume this actually isn't a low compression small cam setup which will also produce excessive heat.

The grill opening on those cars isn't exactly big, so getting in cooler ambient air becomes a bit of a trick especially with the aerodynamics of those cars.

Headers? Are they coated or wrapped?

Take some pics of the area around your radiator.
The headers are not wrapped. I could get them 98% wrapped, but they're already touching the steering box on the DS.

Here's the best photo I have that shows the way the grill/core support/fans are set up. I cut quite a bit out of the core support to increase air flow, but I didn't want to take too much. You are correct though, aerodynamics through the radiator SUCK with this car. There is only about 1" worth of core outside where the cut is.


Think a sheet metal "funnel" behind the grill, and moving the fans around to "pull" would help?



And at first I thought it was a timing issue as well, and it was the first thing I checked... Everything seems to be advancing appropriately. Idle is around 12, and it advances through about 30-32* at 5000.
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Unread 2014-06-30, 05:53 PM   #5
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Yes, some basic sheet metal shrouding up front will most likely help.

I can't remember, but is there an OEM style air damn for the Novas? Anything you can do to create a low pressure area behind the radiator, and a high pressure in front of it will help.

What about vacuum advance? I ASSume if you are running it, then it is connected to a ported vacuum source.


Sweet looking ride BTW.

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Unread 2014-06-30, 07:00 PM   #6
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I'd go with the Roadkill approach. Just take the hood off.
Cost = $0.00
Coolness Factor = High
Result = Cooler temperature
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Unread 2014-06-30, 08:08 PM   #7
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Yes, some basic sheet metal shrouding up front will most likely help.

I can't remember, but is there an OEM style air damn for the Novas? Anything you can do to create a low pressure area behind the radiator, and a high pressure in front of it will help.

What about vacuum advance? I ASSume if you are running it, then it is connected to a ported vacuum source.


Sweet looking ride BTW.

Actually the vac advance is running on manifold pressure... If it was ported, wouldn't that make it burn hotter at idle? (more retard to in high vacuum condition?)
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Unread 2014-06-30, 08:41 PM   #8
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Unless you have some oddball vacuum advance canister, which I doubt, applying vacuum will advance ignition timing. Generally you want to run at base timing at idle, no vacuum applied to the vacuum advance can, and let manifold pressure (vacuum) advance timing at part throttle, hence the use ported vacuum.

There are canisters out there that actually do retard ignition timing when vacuum is applied, but you don't find them on typical Chevy V8 distributors.

Sorry if I am rehashing stuff you already know.
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Unread 2014-06-30, 09:46 PM   #9
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To put your fans in push mode did you change the way the blades face, rather than just switching the power and ground. Also while driving and if the fan is on it could create some weird air pocket and not allow air to pass through the radiator. Most efficient fan setup would be puller set up. Any way to get a slim fan on the back side of the radiator?

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Unread 2014-07-01, 02:11 AM   #10
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To put your fans in push mode did you change the way the blades face, rather than just switching the power and ground. Also while driving and if the fan is on it could create some weird air pocket and not allow air to pass through the radiator. Most efficient fan setup would be puller set up. Any way to get a slim fan on the back side of the radiator?

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This is kind of what i am thinking, those fans look like they could be causing an obstruction for the air to hit the radiator while at speed. It would seem like a nice flat surface would be way more efficient than those fans the way they are placed. The radiator looks plenty big enough for that setup, seems like an airflow issue to me.
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Unread 2014-07-01, 04:27 AM   #11
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Good luck, my dad's last nova had the exact same problem with a built big block. I'll shoot him a text during normal living hours to see if he ever got it fixed and what he did but I know he had a bitch of a time with it.
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Unread 2014-07-01, 09:20 AM   #12
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I find it interesting that on the highway is where the problem is. Typically on the side streets where there isnt as much airflow is where overheating occurs.
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Unread 2014-07-01, 09:24 AM   #13
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out of curiosity, why are you pushing air with the fan instead of pulling? Are you certain they are in fact pushing air?

On the highway you'd have greater flow through the radiator without the fans restricting airflow by putting them on the backside.
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Unread 2014-07-01, 09:36 AM   #14
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out of curiosity, why are you pushing air with the fan instead of pulling? Are you certain they are in fact pushing air?

On the highway you'd have greater flow through the radiator without the fans restricting airflow by putting them on the backside.
I agree with this those fans can't force air through the fins as well as they would by pulling and certainly blocking a good amount of air flow.
I noticed in you sourced the engine from a racing boat, think that might have anything to do with the problem maybe?
Just throwing out ideas. Also just want to comment on how bad ass that nova is. That thing is awesome!
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Unread 2014-07-03, 01:00 AM   #15
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I really appreciate the input guys. I ordered a set of straight blade 13" fans that will be on the back of the radiator. I picked up a 5' x 5' piece of 18ga sheet steel to fab a new air damn/splitter and a new grill for maximum airflow.

Plus while I have the front end apart I've toyed with the idea of lightly painting the core of the radiator black. I've heard it really helps with radiating heat while sitting still. I'd hate to fuck up a $650 radiator though. I figure if it all goes wrong, I can use acetone or something to strip the paint off. MCM did a video about how this works for intercoolers - the theory is still sound for radiators I believe.

Something went wrong. Please make sure you added the video correctly.

Video URL: http://www.youtube.com/watch?v=f1QL9veQaNg


And thanks for the comments. I promise I'm far from finished with this car, so it'll continue to get more absurd / bad ass as the years go by.
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Unread 2014-07-03, 07:40 AM   #16
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Im not sure I'd paint a radiator that, especially since it's "designed" to make it cooler when idling, which isn't where your problem is. That'd be the last thing I'd do.

Move the fans to the back, make sure they are pulling air through and i'm betting you'll be just fine. Thermostat is working correctly i'm assuming? Water pump too?
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Unread 2014-07-05, 08:27 PM   #17
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Took a look with a TIC. The DS is running about 60-80 degrees hotter than the PS.

Strange.


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Unread 2014-07-05, 08:35 PM   #18
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Updates:

I changed the fans to a pair of 1400 cfm straight blade pullers, cut out some more of the core support, flushed /replaced the coolant, changed the oil.

No signs of head gasket problems. Hoses look great. Total timing is now locked at 36* by 3000, (initial around 10).

Still overheating.

New 'stat is next, then a water pump.
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Unread 2014-07-11, 10:38 PM   #19
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I drove the car to fast Fridays tonight with no hood, and that solved the problem. That confirms it's definitely an air flow issue.
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Unread 2014-07-11, 10:39 PM   #20
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I drove the car to fast Fridays tonight with no hood on in that solved the problem. That confirms it's definitely an air flow issue.
The Roadkill method always works.

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Unread 2014-07-12, 03:22 AM   #21
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I drove the car to fast Fridays tonight with no hood, and that solved the problem. That confirms it's definitely an air flow issue.
damn, we didn't get there until late after most everyone left.
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Unread 2014-07-12, 11:05 AM   #22
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Maybe you are under driving the waterpump, have you tried switching pulleys yet? Curious to see whats going on here.. Is the pump a reverse rotation water pump? I didnt see what kind you are running.
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Unread 2014-07-12, 12:42 PM   #23
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It's pretty unlikely that it has a reverse rotation WP as one would have to go out of their way to get one since they were used for a relatively short period of time.

10 model years I think, maybe?

I still think it's an airflow issue.

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Unread 2014-07-12, 12:49 PM   #24
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It's pretty unlikely that it has a reverse rotation WP as one would have to go out of their way to get one since they were used for a relatively short period of time.

10 model years I think, maybe?

I still think it's an airflow issue.

This is true. Didnt think of that..
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Unread 2014-07-25, 12:51 PM   #25
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2x1400 cfm isn't a lot for a motor that size. Mark VIII fans pull around 4500 cfm on high and that's for a much smaller motor. What are the dimensions of your radiator and how much clearance do you have between the rad and the engine?
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