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Discussion Starter #1
I am having heat issues with my 496. I was built with help from Straub and a Local Shop.

When I start it and it runs and get up to temp in stays in the desired range. Fans on at 185 and off at 170. It cycles and all works well.
The problems begin when I drive the car. The temp gets up to 210-215 and stays there while I am driving. It never boils Over.
Once I get back home if I leave it idling in the driveway it drops to 200 but no lower (well i only let it Idle for 10 min or so).

Its an Automatic car, Total Timing is about 35 @3500 rpms, Its bin about 4 years - lost info but I believe this is the radiator I have Northern Radiator | Muscle Car Radiators - 27 3/4 x 18 7/8 x 3 1/8 . I also have Dual Spal Fans (2700 cfm total) with a Shroud on the System. Thermostat is a 160 but I was thinking about changing it to 180 to try and match the Fan switch. Short high-volume Aluminum water pump.

SO My theory at this point is perhaps the Radiator itself is Undersized? I had a few Buddies tell me that I need to get 4th Gen Fans cause they move more air but if air movement was the fix seems like it would not get hot when driving down the Hwy? I am kinda at a Loss - The Radiator is Not rated for the Engine I have - I think I read it was good for 350-400 HP. My setup is supposedly 600+.

That is all I can think of. What do you guys think? AM I missing something? Any tips or Ideas I could try to pinpoint the Issue?

Thanks, Cory C
 

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I don’t think changing the thermostat will make things better unless it failing to open. Can you post a picture of the fan and shroud?
 
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I don’t use electric fans so I’ll let some others chime in but it looks awfully restricted for airflow going down the road.
 

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Cory,

My 496 is 600+ HP as well, in front of a 4L80e. I'm running the exact same Northern radiator, and my engine temps are always in the happy zone. I don't think the radiator is the issue. I'm running dual electric fans as well, but don't recall any specs off the top of my head. I'll go see what I have. Not sure it would matter, but I am running a LWP.
 

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Discussion Starter #6 (Edited)
Thank you, That is HELPFUL

PS - Sixgun, what Pressure Radiator cap are u running?

Cory,

My 496 is 600+ HP as well, in front of a 4L80e. I'm running the exact same Northern radiator, and my engine temps are always in the happy zone. I don't think the radiator is the issue. I'm running dual electric fans as well, but don't recall any specs off the top of my head. I'll go see what I have. Not sure it would matter, but I am running a LWP.
 

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Cory,

My 496 is 600+ HP as well, in front of a 4L80e. I'm running the exact same Northern radiator, and my engine temps are always in the happy zone. I don't think the radiator is the issue. I'm running dual electric fans as well, but don't recall any specs off the top of my head. I'll go see what I have. Not sure it would matter, but I am running a LWP.
Are you running that same shroud? Seems restrictive. I’m running a stock set up but my highway temps improved with a HD clutch fan.
 

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I'm running a 16# radiator cap. I'm also running Northern's Z40015 fan package. It's only rated to 390HP, but has no problem keeping my rig cool and crisp.
 

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Agreed, it most certainly does look restrictive, but I can't argue with how it works.
 

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Once you go over 45 mph or so, you shouldn't need any fan. Both of mine shut off at those speeds after a couple of minutes.
when parked with two good electric fans running full speed it should be pulling more air than a mechanical at idle rpm of 700-900 rpm.

Something else must be going on, water pump,undersized radiator... ?
 

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Agreed, it most certainly does look restrictive, but I can't argue with how it works.
That shroud look like it has two 11" open areas for the electric fans,
what does a stock mechanical shroud have, one open 16"-18" area ?
 

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Discussion Starter #12
That shroud look like it has two 11" open areas for the electric fans,
That's correct - its two 11" Spal fans. Both pump and Radiator are new. I am leaning towards undersized Radiator but I just dont know. I plan to go threw some trouble shooting soon to eliminate any possibilities I can think of B4 i throw new radiator at it. That's Kinda the point of this thread lol =)
 

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Was the block drilled for new style head gaskets?
 

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Discussion Starter #14
Was the block drilled for new style head gaskets?
That I do not know off the top of my head - I cant remember that detail. I can contact the Shop that did the work or look at the invoice and verify that. I worked closely with the Shop that did the milling but I have a horrible memory and this was done 4 years ago
 

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Some head gaskets require the block to be drilled for parallel flow. Usually there is a note in with the head gasket.

i remember doing mine for the Cometics I got. Gen IV 454.

A lot of info here:
 

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Discussion Starter #16
I would have to look at the invoice to confirm but i believe these are the head gaskets I got from Straubtech
 

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Some can be used either way. It wouldn’t hurt to check with those guys. A mismatch could be a problem.
 

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Looks like maybe you could be on to something with the head gasket. I'd contact Straub and see what they say for sure.

As far as the fans,
I know the curved blades run quieter, but the straight bladed fans pull more air. But that's only and issue at lower speeds. If you're hot at highway speeds, definitely not a fan issue.

I'm not at your HP level, I'm around 500 @ the wheels,
my radiator core is 22.5"x 19"x 2.68" with two 1.25" tubes. (Griffen)
two spal straight blade 12" fans 1722 cfm each.
I flog it hard in the heat when I get to autocross(pre-covid) ,with pretty quick back to back runs in 90f+temps, no heat issues at all, 195-200F max.
around town in the summer I'm at 185-190F,on the highway it's stays right around the thermostat temp,180-185.

Hope you figure it out, sounds like a beast of an engine.
 

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Discussion Starter #19
I just Spoke with Chris at Straub Technologies. The Head Gasket did not require any Extra milling work. We talked a little about timing and other possibilities. He was talking about airflow issues at Hwy speeds. I will be doing some trouble shooting this weekend to try and see if I can pinpoint anything. I will keep you guys posted and if U think of anything else please throw it out there.

Thanks, Cory C
 

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Brett - Leander, Texas 1969 SS396
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How 'bout this? If your fans are spinning the wrong direction (push instead of pull), it could be fighting the air that gets forced through when your driving, causing your heat up when driving. Just a thought.

Brett.....
 
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