radiator??

[fishy68]

My 408 runs a little hotter than I like at all speeds. It only has about 2500 miles on it and I had it hot tanked twice and recently flushed it twice and didn't get much out so I'm reasonably sure it's real clean inside. I had a 6 blade water pump on it and thought maybe it just wasn't flowing enough because I have March power and amp serpentine pulleys that slow the pump and alternator down a little so I just installed a high volume 8 blade pump and it made very little difference. I'm sure it's not running lean, got a A/F gauge in it and have read the plugs and if anything it's a tad rich, but not much. Timing is dialed in good too so I'm sure it's not the tune. First I had a 6 blade flex fan with a shroud properly mounted and in my quest to find lower temps I have tried a 16" electric puller fan that made absolutely no difference except tax the electrical system more. It'll idle all day without going over 185 but as soon as I get on the road it goes up to 210~215 pretty fast. I've tried 2 high flow 180 thermostats with the exact same result. I'd like to get it down to 200 or below if possible. I used a laser temp gun and it shows the water coming out of the radiator is less than 10 degrees cooler than what's going in. IMO the radiator isn't doing it's job well enough because it has plenty of air flow as you can feel it sucking all the way to the front of the grills. It's an aftermarket aluminum radiator with a core size of 19.25" x 18.5". It kept my old loose goose 360 (approx. 350 hp) cool but not the 408 (approx. 450-460 hp). The core opening is 3" wider than the current radiators core so I can go bigger. When looking at what Summit had to offer I see they have what they call a triple pass radiator that's supposed to be better than a std. single pass but I've never heard of them or saw them used. Does anyone have any input on them? What's everybody else running with their 450'ish hp engines? Also can anyone tell me why a cross flow radiator is supposed to be better than the old style down flow? For the last 30 yrs. everyone has said cross flow is better but no one I know knows why.

 

[camd64]

Have you checked for any cold spots on the radiator with your temp gun? How close is the fan to the radiator? The only reason I found that made any sense when I too was looking at crossflow rads. was the tube length is generally longer so more time to get the water cooler. That would make sense since newer cars have less frontend height so it would make it necessary on certain models. On our era cars though I don't think it would be anything necessary more than just a good working standard downflow rad.

 

[autoxcuda]

Weird that is will idle fine. But only when moving, it will get hot. Usually that's radiator clogged or too small.

What is the exact radiator you have now? How many rows?

Have you tried an 17-18" factory viscous fan? Those blades are much wider than a flex fan.

I have a 421 stroker with about 450 HP and cam close to yours: Comp XS274S . I get 15-20 degrees from top to bottom of radiator.

Could you old motor have dumped rust/debris in your radiator and clogged certain portions?

Have you heat gunned different sections of your radiator core to see if maybe a certain section is clogged?

When I did my motor I hand picked the coolant passages clean of rust build up and debris. And water+shop air gunned the passages. I can't see how modern hot tanking could have chipped off that rust scale.

 

[fishy68]

Have you checked for any cold spots on the radiator with your temp gun? How close is the fan to the radiator? The only reason I found that made any sense when I too was looking at crossflow rads. was the tube length is generally longer so more time to get the water cooler. That would make sense since newer cars have less frontend height so it would make it necessary on certain models. On our era cars though I don't think it would be anything necessary more than just a good working standard downflow rad.

The temp seems to be uniform everywhere but my temp gun is kinda hard to get good readings off shiny objects. Right now I have the electric fan on it and it's about 1/4" away. When I had a flex fan on it was 3/4" away and centered in the shroud (1/2 in and 1/2 out). With both fans it pulls a lot of air. I can feel it at the front of the grill with either. I never compared tube length on down vs. cross flow but you may be right.

 

[fishy68]

Weird that is will idle fine. But only when moving, it will get hot. Usually that's radiator clogged or too small.

What is the exact radiator you have now? How many rows?

Have you tried an 17-18" factory viscous fan? Those blades are much wider than a flex fan.

I have a 421 stroker with about 450 HP and cam close to yours: Comp XS274S . I get 15-20 degrees from top to bottom of radiator.

Could you old motor have dumped rust/debris in your radiator and clogged certain portions?

Have you heat gunned different sections of your radiator core to see if maybe a certain section is clogged?

When I did my motor I hand picked the coolant passages clean of rust build up and debris. And water+shop air gunned the passages. I can't see how modern hot tanking could have chipped off that rust scale.

Sure is weird isn't it!

It's a 2 row. Their 1" rows. I don't remember the brand but I bought it from FBO. I told Don I was planning on building a 408 that'd make about 450 hp and he said it'd be plenty radiator for that.

No I haven't tried a viscous fan but that was my next step. But by how much air I feel it moving it'd surprise me it'd help.

Thanks for confirming the temp drop on yours. I was thinking I should see at least a 15 degree drop.

My old 360 was loose but I don't think it was rusty. From what I can tell the temp is real uniform all over the radiator but I will say this temp gun seeems kinda finicky when it comes to trying to get a reading off a shiny object. When I look down the fill neck it looks like it's flowing good. Wish I had a scope so I could look down inside the inlet side to verify it's not clogged as it sure seems like a radiator issue to me.

What radiator are you using?

I also spent a lot of time hand cleaning every passage when I built my 408. I shined a light through every passage and used anything and everything including 100+ psi of air to blow every last bit of trash out of it that I could.

 

[pettybludart]

Hi Tracy,I,ve been racing my 408(410)all summer long and have had no overheating problems.I run a stock 73 318 2 core rad(re-cored)with a 7 blade clutch fan,eddie alumi waterpump and add a small bottle of water-wetter(BeKool)with a 180 stat...no fan shroud.My car never goes over 180,even on the hottest summer days.This summer alone I have well over 125 passes and never once went over 180.Alot of racers kinda laugh at my simple setup,but hey..it works.I,m gonna say you have some blockage in your rad.I,d try some additive to your water or antifreeze??Maybe bad/cheap antifreeze??Good luck.

 

[fishy68]

Hi Tracy,I,ve been racing my 408(410)all summer long and have had no overheating problems.I run a stock 73 318 2 core rad(re-cored)with a 7 blade clutch fan,eddie alumi waterpump and add a small bottle of water-wetter(BeKool)with a 180 stat...no fan shroud.My car never goes over 180,even on the hottest summer days.This summer alone I have well over 125 passes and never once went over 180.Alot of racers kinda laugh at my simple setup,but hey..it works.I,m gonna say you have some blockage in your rad.I,d try some additive to your water or antifreeze??Maybe bad/cheap antifreeze??Good luck.

Yep.. I've seen setups like that many times that work good and guys with aftermarket stuff that looks trick doesn't work as good. I tried water wetter and it did help. I do have a 33% mix of antifreeze. Going from a 50/50 antifreeze/water mix to the 33% mix with water wetter dropped it a good 10 degrees.

BTW: how hot was your summer up there this year? It was well over 100 for nearly 4 weeks straight here. Hottest summer on record. I didn't even get the cuda out then it was so freakin hot. I'd hate to imagine how hot it would have ran in that temp.

 

[autoxcuda]

Yep.. I've seen setups like that many times that work good and guys with aftermarket stuff that looks trick doesn't work as good. I tried water wetter and it did help. I do have a 33% mix of antifreeze. Going from a 50/50 antifreeze/water mix to the 33% mix with water wetter dropped it a good 10 degrees.

BTW: how hot was your summer up there this year? It was well over 100 for nearly 4 weeks straight here. Hottest summer on record. I didn't even get the cuda out then it was so freakin hot. I'd hate to imagine how hot it would have ran in that temp.

I drive and fart around town in stoplight traffic. Was 100 degrees out here on and off last few weeks. It's the car I get groceries in.

No overheating here. I have a 4 row Champion, Milodon water pump, Milodon thermostat (to Milodon spec only from US plant)

On the highway with steady airflow no issues at all. About 170 to 180 degrees cruising at 70-80 mph at 3500-3800 rpm. Even in 100 degree heat outside.

 

[winstoninwisc]

like she said get a 180 and punch 2 holes in it with a screwdriver just for slow flo but gets the job done other wise get scoops theylok nice find old dart scoops

 

[winstoninwisc]

hey check your water pump also may have broken blade or slippn
other wise go aliminum or i have an old 1 thqat dopest leak but io dont think thats your prob

 

[winstoninwisc]

check for casting in air gap its not letting fluid move when your rpms are higher
like reverb hold back or your water pump has a busted blade

 

[fishy68]

I drive and fart around town in stoplight traffic. Was 100 degrees out here on and off last few weeks. It's the car I get groceries in.

No overheating here. I have a 4 row Champion, Milodon water pump, Milodon thermostat (to Milodon spec only from US plant)

On the highway with steady airflow no issues at all. About 170 to 180 degrees cruising at 70-80 mph at 3500-3800 rpm. Even in 100 degree heat outside.

When I replaced my original radiator I ordered a Champion. What a POS. Looked like a kid welded it together and it was twisted. I had a thread about it a long time back, it's been so long (2-3 yrs.) I wouldn't be able to find it easy. I've heard they work good if you get a good one. Oh yeah, mine was also supposed to bolt right in and the factory fan shroud work. Not even close. I lost $30 in shipping it back to them. Glad to hear you got a good one.

What Milodon thermostat are you using (part #)?

Thanks

 

[fishy68]

Update, I installed a new Autometer temp gauge and cruised it around for about an hour (all the time I had) and it never went above 185 so now I'm wondering if it was never running as hot as I thought and my high dollar laser temp gun is off??? Going to pick up a new temp gun next week and see what it says. Thanks for the input guys

 

[autoxcuda]

When I replaced my original radiator I ordered a Champion. What a POS. Looked like a kid welded it together and it was twisted. I had a thread about it a long time back, it's been so long (2-3 yrs.) I wouldn't be able to find it easy. I've heard they work good if you get a good one. Oh yeah, mine was also supposed to bolt right in and the factory fan shroud work. Not even close. I lost $30 in shipping it back to them. Glad to hear you got a good one.

Yes, my Champion was tweaked too. I just un-tweaked it. And you are correct, the factory fan shroud would not fit at all.

I knew from the price not to have my hopes up too high on that. IIRC, it was after you posted your experiance here on FABO. I remember reading it. So I was ready for it.

.

[/What Milodon thermostat are you using (part #)?

Thanks

160 degree. Pn: 16405

160° Thermostat - Chrysler (All) and Ford 390-428 (pre '67) 16405

 

[fishy68]

Yes, my Champion was tweaked too. I just un-tweaked it. And you are correct, the factory fan shroud would not fit at all.

I knew from the price not to have my hopes up too high on that. IIRC, it was after you posted your experiance here on FABO. I remember reading it. So I was ready for it.

.

160 degree. Pn: 16405

160° Thermostat - Chrysler (All) and Ford 390-428 (pre '67) 16405

Sounds like you got lucky. Mine was twisted so bad and the welds looked terrible so I was affraid to try to tweak it in shape for fear it'd leak. Tnx for the part # on the Milodon thermost.