Do all 67-69 small block Barracuda's run hot? Rant

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bluefish1967

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Owned our convertible for 12 years now, and have tried various combinations of radiators, water pumps, shrouds , fan blades etc. to no avail. Finally determined ( in my head LOL ) that it was an engine problem after finding 18% - 24% leak down in the cylinders.
Built a fresh 340. everything new. Engine ran at a rock steady 180 over the winter months. Now that the heat and humidity is back. it's starting up again. Engine runs 180 for a while, then shoots up to 210. After a while, it then skyrockets. Happens when idling for a long time
Have again verified timing and harmonic balancer, carb jetting etc. Has a brand new 22 inch US radiator's 3 core radiator, larger than the 2 core original. Seems like the engine compartment is so small that the heat gets trapped in when you idle for a long time. Can see the heat waves radiating off the hood after you idle for a while, can't begin to touch the hood. Everything's fine when rolling down the road. Any thoughts?
 
I've read a bunch of posts lately about the champion radiator with a clutch fan w/shroud.

I personally use a two speed taurus fan. But it won't fit without modifications and upgraded charging.
 
It's not the size of engine compartment. Yes, the heat does play a factor. Are you running a shroud? It does help. Your re-built motor. What is the over bore?
 
To answer your question, no they dont all run hot. You say its fine going down the road, that says your radiator is probally fine, suggests that its a lack of airflow while sitting still. Fan/shroud combo, and correct pulleys are the key here. Also make sure the hood is sealed to the top of the rad support
 
A good 180 or 195 T stat helps keep water in the heads longer and has cured a lot of heating issues.
 
R4Sedan said:
It's not the size of engine compartment. Yes, the heat does play a factor. Are you running a shroud? It does help. Your re-built motor. What is the over bore?
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Current combo is .020 over 340, stock cam and exhaust manifolds. Wiend intake with Holley 570 carb.
Cooling system consist of New 3 core radiator, Milidon performance water pump and matching thermostat, new factory fan shroud and MP clutch fan from Mancini racing. Fan is app. 1/2 inch from radiator.
Base timing is 10 degrees, engine idles smooth with 15 inches of vacuum at idle in gear.
Last night, I replaced the MP clutch fan with a solid 7 blade fan. Have not had time to test it other than it seemed to be louder at idle and was pulling more air through the radiator. We'll see.
 
replicaracer43 said:
To answer your question, no they dont all run hot. You say its fine going down the road, that says your radiator is probally fine, suggests that its a lack of airflow while sitting still. Fan/shroud combo, and correct pulleys are the key here. Also make sure the hood is sealed to the top of the rad support
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Pulleys are the factory originals. as far as I know. Never gave it any thought about the hood being sealed to the radiator support...Have to give that a look.
 
Best read so far is the quote below.

replicaracer43 said:
To answer your question, no they dont all run hot. You say its fine going down the road, that says your radiator is probally fine, suggests that its a lack of airflow while sitting still...
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I run a factory flex fan, no shroud, recored original radiator to 3 cores, ac water pump, and a 160 degree thermostat. No problems, ever. Even the 383.
 
195 is more thermodynamically efficient than 160 or 180. Many cars won't maintain 160, anyway, so it's the same as running without a thermostat -- it would be wide open all the time in the summer. Timing definitely can affect the running temp, as does low oil level. The solid fan will pull more air at idle and at low speed, which is when you need it. The clutch actually makes the fan less effective, with the idea of saving horsepower at higher RPM, but it's a trade off. You might want a thermostatic fan clutch instead, that tightens up at higher temps.
 
mderoy340 said:
You need to put more initial timing in it.
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Got some time in tonight on the car.
When hooking up the timing light and vacuum gauge, noticed 2 things.
First, the lock-down bolt on the distributor was loose. Timing was at 20 degrees instead of 10 where I had set it. Also, the cap to block off the vacuum port under the carb was split.
So i adjusted the base timing to 12 degrees, and re-adjusted the idle mix with the vacuum gauge. Have 18 inches of vacuum at idle.
Did a short test in the garage, so far the temp stayed at 180. It's not as hot or humid tonight, but it's a start. Will give it a test drive this weekend. Thanks for all of the input. Larry
 
Hey Larry, this might sound a little funny to you but go to your local auto parts store and buy a bottle of water wetter. My 66 Barracuda was running a little hot at idle and a friend of mine told me that he adds a bottle or two to every build. Guess what my Barracuda can sit there and idle for a long time and it won't over heat anymore, give it a try.
Bob
 
AJ/FormS said:
Well it sounds like you have it under control.
But if it acts up again, maybe have another look at the LD test.....
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Yeah, this is a fresh rebuild, but a long-term project. Have less than 50 miles on the new engine. Haven't had time to do a leak-down on this one yet. Maybe this weekend?
 
bluefish1967 said:
Yeah, this is a fresh rebuild, but a long-term project. Have less than 50 miles on the new engine. Haven't had time to do a leak-down on this one yet. Maybe this weekend?
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Sounds pretty simple! The factory componets did the job just fine back in the day! Do not over think it!!! Make sure you have the hood to core support seal and all the pieces are up to the task. Aftermarket radiators are not all the same, and up to factory spec! I would suggest a factory radiator design from Glen Rays and all the complementing pieces. Sometimes we try to enhance something that was proven fine for no reason other than to seemingly make it better in our mind. Use the correct thermostat and high flow is smart. "Kiss" it is my moto!
 
My rad, shroud,and 7-blade fan all are circa 1973 teener A/C stuff. There are three non stock items in the system; The Milodon pump and stat, and the Ford Thermostatic clutch.
The pump is just an 8 blader with an anti-cavitation plate.
This combo flat out works.
 
What is the antifreeze concentration? 50/50 is a good all around mixture. But if you increase the amount of antifreeze in the ratio, say to 70/30, you reduce the coolant's ability to shed heat. If all else fails, try a 30/70 mixture….30% antifreeze, 70% water.
 
69swinger340391 said:
What is the antifreeze concentration? 50/50 is a good all around mixture. But if you increase the amount of antifreeze in the ratio, say to 70/30, you reduce the coolant's ability to shed heat. If all else fails, try a 30/70 mixture….30% antifreeze, 70% water.
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Not sure exactly on the mix other than it is not 50/50. Probably more like 70/30. One more thing to look at. Thanks.
 
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